The abstracts of papers published from 2013-2015 are excerpted below. Visit Club du Soleil for the remainder of their compilation extending back to 2010. Hundreds of other papers finding evidence of solar influence of climate published prior to 2010 may be found in the citations for these more recent papers.
This citation list is incomplete even for the last few years, as many posts at the Hockey Schtick and elsewhere have highlighted numerous additional published papers finding solar influence upon climate and solar amplification mechanisms that do not appear in the Club du Soleil compilation of citations below.
The real hockey stick |
Papers reported in 2015
Solar Irradiance Variability and Climate
Solanki et al. 2013 Annu. Rev. Astron. Astrophys. 51, 311-351
The brightness of the Sun varies on all time scales on which it has been
observed, and there is increasing evidence that it has an influence on
climate. The amplitudes of such variations depend on the wavelength and
possibly on the time scale. Although many aspects of this variability
are well established, the exact magnitude of secular variations (going
beyond a solar cycle) and the spectral dependence of variations are
under discussion. The main drivers of solar variability are thought to
be magnetic features at the solar surface. The climate reponse can be,
on a global scale, largely accounted for by simple energetic
considerations, but understanding the regional climate effects is more
difficult. Promising mechanisms for such a driving have been identified,
including through the influence of UV irradiance on the stratosphere
and dynamical coupling to the surface. Here we provide an overview of
the current state of our knowledge, as well as of the main open
questions.
Robust Response of the East Asian Monsoon Rainband to Solar Variability
Zhao and Wang 2014 Journal of Climaten 27, 3043-3051
This study provides evidence of the robust response of the East Asian
monsoon rainband to the 11-yr solar cycle and first identify the exact
time period within the summer half-year (1958-2012) with the strongest
correlation between the mean latitude of the rainband (MLRB) over China
and the sunspot number (SSN). This period just corresponds to the
climatological-mean East Asian mei-yu season, characterized by a
large-scale quasi-zonal monsoon rainband (i.e., 22 May-13 July). Both
the statistically significant correlation and the temporal coincidence
indicate a robust response of the mei-yu rainband to solar variability
during the last five solar cycles. During the high SSN years, the mei-yu
MLRB lies 1.2 ° farther north, and the amplitude of its interannual
variations increases when compared with low SSN years. The robust
response of monsoon rainband to solar forcing is related to an anomalous
general atmospheric pattern with an up-down seesaw and a north-south
seesaw over East Asia.
Cosmic ray event of A.D. 774-775 shown in quasi-annual 10Be data from the Antarctic Dome Fuji ice core
Miyake et al. 2015 Geophysical Research Letters
14C content in tree rings and 10Be concentration records in polar ice
core provide information about past cosmic ray intensities. The A.D.
774-775 cosmic ray event has been identified by 14C measurement in
several tree rings from all over the world. Although the quasi-decadal
10Be Dome Fuji data in the Antarctic ice core also shows a sharp peak
around A.D. 775, annual 10Be variations in the Dome Fuji core or in
other cores have not been revealed. We have measured quasi-annual 10Be
concentrations from approximately A.D. 763-794 in the Dome Fuji ice
core, and detected a clear increase (c. 80% above the baseline) in 10Be
concentration around A.D. 775. However, an accurate height of this
increase is not straightforwardly estimated due to the background
variation in 10Be concentration. The 10Be increase can be due to the
same cosmic ray event as shown in the 14C content in A.D. 774-775.
Abrupt Holocene Indian Summer Monsoon failures: A primary response to solar activity?
Xu et al. 2015 The Holocene
Knowledge of the millennial abrupt monsoon failures is critical to
understanding the related causes. Here, we extracted proxy indices of
Indian Summer Monsoon (ISM) intensity during the early to mid-Holocene,
from peat deposits at Lake Xihu, in southwestern China. There are a
series of abrupt, millennial-scale episodes of ISM weakening inferred
from the Lake Xihu records, which are generally synchronous with those
inferred from other archives over ISM areas. An important feature is
that the ISM failures inferred from the Lake Xihu proxy indices
synchronize well with abrupt changes in solar activity. We argue that
changes in solar activity play a primary role in producing most of these
millennial ISM failures, while some other causes, including freshwater
outbursts into the North Atlantic Ocean and changes in sea surface
temperatures of the eastern tropical Pacific Ocean, may have also
exerted influences on parts of the millennial ISM failures.
Solar forcing of Earth's surface temperature in PMIP3 simulations of the last millennium
Le 2014 Atmospheric Science Letters
This study quantitatively diagnose the linkage between Total Solar
Irradiance (TSI) and Earth's near-surface air temperature (TAS) of past
1000-year as simulated by Paleoclimate Modeling Intercomparison Project 3
(PMIP3) models. The results demonstrate that there is causal feedback
of TAS from TSI variations, especially in the tropical and subtropical
regions. The consistency between models in simulating solar signal in
TAS responses is significant in these regions with more than 70%
selected models showing agreement. There is no agreement between models
in simulating TSI-TAS relationship in mid and high latitude regions.
papers reported in 2014
Evidence for the Gleissberg solar cycle at the high-latitudes of the Northern Hemisphere
Ogurtsov et al. 2014 Advances in Space Research
Time evolution of growing season temperatures in the Northern Hemisphere
was analysed using both wavelet and Fourier approaches. A century-scale
(60-140 year) cyclicity was found in the summer temperature
reconstruction from the Taymir peninsula (72 N, 105 E) and other
high-latitude (60-70 N) regions during the time interval AD 1576-1970.
This periodicity is significant and consists of two oscillation modes,
60-70 year and 120-140 year variations. In the summer temperatures from
the Yamal peninsula (70 N, 67 E) only a shorter-term (60-70 year)
variation is present. A comparison of the secular variation in the
Northern Hemisphere temperature proxies with the corresponding
variations in sunspot numbers and the fluxes of cosmogenic 10Be in
Greenland ice shows that a probable cause of this variability is the
modulation of temperature by the century-scale solar cycle of
Gleissberg. This is consistent with the results obtained previously for
Northern Fennoscandia (67-70 N, 19-33 E). Thus, evidence for a
connection between century-long variations in solar activity and climate
was obtained for the entire boreal zone of the Northern Hemisphere.
Ultraviolet radiation exposure of a high arctic lake in Svalbard during the Holocene
Nevalainen et al. 2014 Boreas
Long-term fluctuations in lake-water optical properties were examined
using a Holocene sediment sequence and multi-proxy palaeolimnological
approach in Lake Einstaken, Nordaustlandet, Svalbard. UV-absorbance of
sedimentary cladoceran remains provided information on underwater UV
exposure and changes in lake-catchment coupling processes were inferred
from sediment geochemistry. In addition, aquatic community succession
was used as an indicator for lake-water bio-optical properties and a
Holocene record of sun activity (sunspots) was utilized to evaluate
long-term solar forcing. The results indicated that the UV-absorbance of
cladoceran remains was highest (i.e. maximum UV-induced pigmentation)
for a short period during the early Holocene and for several millennia
during the mid-Holocene. Sun activity was high during these time
intervals, probably impacting the UV intensities, but it is probable
that the amount of UV-attenuating compounds (e.g. dissolved organic
carbon (DOC)) also significantly affected the underwater UV environment
and were low during high UV exposure. Benthic autotrophic communities
also responded to the millennial changes in lake-water optical
properties. UV-resistant Nostoc cyanobacterial colonies were established
during the mid-Holocene, indicative of high underwater UV intensities,
and Fontinalis mosses thrived during the early Holocene, indicating a
highly transparent water column. The results further suggested that
underwater UV exposure decreased during the late Holocene, which is
probably attributable to increased DOC and decreased solar forcing.
Owing to the location of Lake Einstaken and its catchment in the
periglacial barren landscape of the polar desert, the fluctuations of
bio-optical lake-water properties were apparently forced by postglacial
environmental processes and Holocene climate development. These factors
controlled sea shoreline proximity, water discharge, ice-cover duration
and littoral-benthic primary production and further affected the
underwater UV environment. Although the role of solar forcing cannot be
underestimated, the current record emphasizes the role of
climate-mediated lake-catchment interactions in impacting bio-optical
properties and UV exposure of high arctic aquatic systems.
Origin and palaeoenvironmental significance of C25 and C27n-alk-1-enes in a 25,000-year lake-sedimentary record from equatorial East Africa
van Bree et al. 2014 Geochimica et Cosmochimica Acta
We studied the distribution of long-chain alkenes (n-C23 to n-C31) in
well-dated sediments from Lake Challa, a deep crater lake near Mt.
Kilimanjaro in equatorial East Africa, to reveal signatures of
palaeo-environmental and palaeo-climatic changes affecting the
production of these compounds during the last 25 kyr. The apolar
fractions of organic sediment extracts dated to the last 16 kyr showed
an unusual dominance of d13C-depleted n-C25:1 and n-C27:1 alk-1-enes.
These alkenes were not detected in soil and litter from near the
shoreline and from the inner rim of the crater, pointing to an
autochthonous, aquatic source. Analysis of suspended particulate matter
indicated that the n-alk-1-enes are produced in the well-oxygenated
upper 30 m of the water column, indicating a phytoplanktonic origin.
Sedimenting particles collected monthly from December 2006 to November
2007 showed increased fluxes of n-alk-1-enes following the locally
prominent short rain season in November-December. Green algae and/or
cyanobacteria were identified as candidate sources of these alkenes.
Production of the n-C25:1 and n-C27:1 alkenes in Lake Challa was much
reduced during the Last Glacial Maximum and early late-glacial period,
suggesting a temperature or CO2 effect on habitat suitability. We
explored the potential of n-alk-1-ene accumulation rates, and of a
derived Alkene Index [n-C27:1]/([n-C25:1] + [n-C27:1]), to record
longer-term climatic changes. The Alkene Index record of Lake Challa
over the past 25 kyr shows clear periodicity with a dominant frequency
of c. 2.3 kyr, potentially indicative of monsoon variability directly or
indirectly forced by variation in solar radiation.
Influence of Solar Activity on the Climate Change
Kovalenko and Zherebtsov 2014 Atmospheric and Oceanic Optics 27, 506-510
We discuss problems which are of main importance for understanding the
nature of climate changes in the 20th century and basic physical
processes responsible for these changes. A possible role of solar
activity in the Earth's climate changes in the past and future is
considered. As shown, physical mechanisms which can provide for the
solar variability effect on the weather and climate are reduced to the
control of the energy flux from the Earth to space. A special emphasis
is given on the solar activity effect on climatic characteristics of the
troposphere through the atmospheric electricity. We consider
peculiarities of the response of thermal and dynamic regimes of the
World Ocean and atmosphere to solar activity changes and processes in
the atmosphere, ocean, and cryosphere. We also show and discuss results
of the analysis of regularities and peculiarities of troposphere and the
ocean surface temperature response to both isolated heliogeophysical
disturbances and long term changes in solar and geomagnetic activity.
Modulation of UK lightning by heliospheric magnetic field polarity
Owens et al. 2014 Environmental Research Letters 9 115009
Observational studies have reported solar magnetic modulation of
terrestrial lightning on a range of time scales, from days to decades.
The proposed mechanism is two-step: lightning rates vary with galactic
cosmic ray (GCR) flux incident on Earth, either via changes in
atmospheric conductivity and/or direct triggering of lightning. GCR flux
is, in turn, primarily controlled by the heliospheric magnetic field
(HMF) intensity. Consequently, global changes in lightning rates are
expected. This study instead considers HMF polarity, which doesn't
greatly affect total GCR flux. Opposing HMF polarities are, however,
associated with a 40-60% difference in observed UK lightning and thunder
rates. As HMF polarity skews the terrestrial magnetosphere from its
nominal position, this perturbs local ionospheric potential at high
latitudes and local exposure to energetic charged particles from the
magnetosphere. We speculate as to the mechanism(s) by which this may, in
turn, redistribute the global location and/or intensity of thunderstorm
activity.
Frequency Characteristic of Response of Surface Air Pressure to Changes in Flux of Cosmic Rays
Bogdanov 2014 Geomagnetism and Aeronomy 54, 813-818
We compare the series of daily-average values of the surface air
pressure for De Bilt and Lugano meteorological stations with subtracted
linear trends and seasonal harmonics, as well as the series of the flux
of galactic cosmic rays (GCRs) at Jungfraujoch station with subtracted
moving average over 200 days. Using the method of superposed epochs, we
show that the Forbush decreases at both stations are accompanied by
increased pressure. Spectral analysis allows us to conclude that the
analyzed series are characterized by nonzero coherence in almost the
entire frequency range: from 0.02 day-1 up to the Nyquist frequency of
0.5 day-1. Using changes in the GCR flux as a probing signal, we obtain
amplitude-frequency characteristics of the pressure reaction. For both
stations, these characteristics are in qualitative agreement with each
other and indicate that the atmospheric response can be described by a
second-order linear dynamic system that has wide resonance with a
maximum at a frequency of 0.15 day-1.
Do sunspot numbers cause global temperatures? Evidence from a frequency domain causality test
Gupta et al. 2014 Applied Economics
This article applies the causality test in the frequency domain,
developed by Breitung and Candelon (2006), to analyse whether sunspot
numbers (used as a partial approximation to solar irradiance) cause
global temperatures, using monthly data covering the time period
1880:1-2013:9. While standard time domain Granger causality test fails
to reject the null hypothesis that sunspot numbers do not cause global
temperatures for both full and sub-samples (identified based on tests of
structural breaks), the frequency domain causality test detects
predictability for both the full-sample and the last sub-sample at short
(2-2.6 months) and long (10.3 months and above) cycle lengths,
respectively. Our results highlight the importance of analysing
causality using the frequency domain test, which, unlike the time domain
Granger causality test, allows us to decompose causality by different
time horizons, and hence, could detect predictability at certain cycle
lengths even when the time domain causality test might fail to pick up
any causality. Further, given the widespread discussion in the
literature, those results for the full-sample causality, irrespective of
whether it is in time or frequency domains, cannot be relied upon when
there are structural breaks present, and one needs to draw inference
regarding causality from the sub-samples, we can conclude that there has
been an emergence of causality running from sunspot numbers to global
temperatures only recently at cycle length of 10.3 months and above.
A 2700 cal yr BP extreme flood event revealed by sediment accumulation in Amazon floodplains
Moreira-Turcq et al. 2014 Palaeogeography, Palaeoclimatology, Palaeoecology 415, 175-182
Climatic conditions are one of the most important factors affecting
hydrological processes in fluvial systems. Higher discharges are
responsible for higher erosion, greater transport, and also higher
deposition. Consequently, sediment accumulation in Amazonia floodplain
river-connected lakes can be directly related to hydrological patterns
of the Amazon River mainstream. In this context, we analyzed five
sediment cores taken in two floodplain systems situated in the lower
Amazon River, to investigate sediment accumulation patterns during the
Holocene. Our records show abrupt fluctuations in sedimentation rates in
lakes that can reach more than 2 cm/yr during some periods. We find
that in all cores, sediment stratigraphy is characterized by packages of
sediments of uniform age, which are typically 10-80 cm thick and
present a variegated color. The 14C age of the upper package is about
2700 cal yr BP. During this abrupt event, sediment accumulation rates in
floodplain lakes can be at least 200 times higher than those of
"normal" periods. This sedimentation event is interpreted as being the
consequence of one or several successive extreme floods. The 2700 cal yr
BP event has been also observed in other sites in South America and
other regions in the world, although different impacts can be observed
in each system. This event probably corresponds to a conjunction of
favorable conditions for extreme Amazon discharge associated with the
Middle to Late Holocene increase of austral summer insolation and shifts
of the Intertropical Convergence Zone (ITCZ) from northern to southern
positions. In this context, a marked negative peak in solar irradiance
at 2700 cal yrs BP seems to have provoked cooling on the continents and a
southward shift of the ITCZ associated with a probable reduction in the
Atlantic Meridian Overturning Circulation.
Ultra-high-resolution paleoenvironmental records via direct laser-based analysis of lipid biomarkers in sediment core samples
Wörmer et al. 2014 PNAS
Lipid biomarkers in geological samples are important informants
regarding past environments and ecosystems. Conventional biomarker
analysis is labor intensive and requires relatively large sediment or
rock samples; temporal resolution is consequently low. Here, we present
an approach that has the potential to revolutionize paleoenvironmental
biomarker research; it avoids wet-chemical sample preparation and
enables analysis of biomarkers directly on sediment cores at
submillimeter spatial resolution. Our initial application to a sediment
core deposited during the Holocene climate optimum in the Mediterranean
Sea reveals a new view of how small-scale variations in lipid
distribution are integrated into commonly reported signals obtained by
conventional analysis and demonstrates a strong influence of the c.200-y
de Vries solar cycle on sea-surface temperatures and planktonic
archaeal ecology.
A 449 year warm season temperature reconstruction in the southeastern Tibetan Plateau and its relation to solar activity
Duan & Zhang 2014 Journal of Geophysical Research: Atmospheres
There is a close relationship between solar activity and the Earth's
surface temperature, but this relationship has weakened with recent
global warming. To better understand this puzzle, temperature records
need to be extended, and the relationship between long-term variation in
temperature and solar activity needs to be examined. In this study, we
reconstruct April-September temperature variation back to 1563 using
tree ring maximum late wood density (MXD) data from Balfour spruce in
the southeastern Tibetan Plateau (TP). Spatial correlation analysis
indicates that our reconstruction is representative of temperature
variability over the large-scale TP. On the 22 year time scale, the
reconstructed April-September temperature corresponds generally to solar
activity over the past three centuries. Spectral analyses also indicate
that the significant periodicities of c. 11 years, 54 years, and 204
years observed in the MXD chronology correspond to the Schwabe cycle,
the fourth harmonic of the Suess cycle, and the Suess solar cycle,
respectively. However, disparities between temperature change and solar
activity are identified in two periods, the 1880s-1900s and the
1980s-present. These results suggest that solar forcing is the critical
driver for long-term temperature variability in the TP, but other
factors may uncouple surface temperature and solar activity in some
periods. One possible cause of the weak effect of solar activity on
temperature during the 1880s-1900s is internal climate variability,
while human-activity-induced greenhouse gas emissions have likely
superseded solar forcing as the major driver of the rapid warming
observed since the 1980s.
Mount Logan ice core record of tropical and solar influences on Aleutian Low variability: 500-1998 A.D.
Osterberg et al. 2014 Journal of Geophysical Research: Atmospheres
Continuous, high-resolution paleoclimate records from the North Pacific
region spanning the past 1500 years are rare; and the behavior of the
Aleutian Low (ALow) pressure center, the dominant climatological feature
in the Gulf of Alaska, remains poorly constrained. Here we present a
continuous, 1500 year long, calibrated proxy record for the strength of
the wintertime (December-March) ALow from the Mount Logan summit (PR
Col; 5200 m asl) ice core soluble sodium time series. We show that ice
core sodium concentrations are statistically correlated with North
Pacific sea level pressure and zonal wind speed. Our ALow proxy record
reveals a weak ALow from circa 900-1300 A.D. and 1575-1675 A.D., and a
comparatively stronger ALow from circa 500-900 A.D., 1300-1575 A.D., and
1675 A.D. to present. The Mount Logan ALow proxy record shows strong
similarities with tropical paleoclimate proxy records sensitive to the
El Niño-Southern Oscillation and is consistent with the hypothesis that
the Medieval Climate Anomaly was characterized by more persistent La
Niña-like conditions while the Little Ice Age was characterized by at
least two intervals of more persistent El Niño-like conditions. The
Mount Logan ALow proxy record is significantly (p < 0.05) correlated
and coherent with solar irradiance proxy records over various time
scales, with stronger solar irradiance generally associated with a
weaker ALow and La Niña-like tropical conditions. However, a step-like
increase in ALow strength during the Dalton solar minimum circa 1820 is
associated with enhanced Walker circulation. Furthermore, rising CO2
forcing or internal variability may be masking the twentieth century
rise in solar irradiance.
The cause of solar dimming and brightening at the Earth's surface during the last half century: Evidence from measurements of sunshine duration
Stanhill et al. 2014 Journal of Geophysical Research: Atmospheres
Analysis of the Angstrom-Prescott relationship between normalized values
of global radiation and sunshine duration measured during the last 50
years made at five sites with a wide range of climate and aerosol
emissions showed few significant differences in atmospheric
transmissivity under clear or cloud-covered skies between years when
global dimming occurred and years when global brightening was measured,
nor in most cases were there any significant changes in the parameters
or in their relationships to annual rates of fossil fuel combustion in
the surrounding 1° cells. It is concluded that at the sites studied
changes in cloud cover rather than anthropogenic aerosols emissions
played the major role in determining solar dimming and brightening
during the last half century and that there are reasons to suppose that
these findings may have wider relevance.
Holocene cyclic climatic variations and the role of the Pacific Ocean as recorded in varved sediments from northeastern China
Chu et al. 2014 Quaternary Science Reviews 102, 85-95
We present an n-alkane and compound-specific carbon isotope record of
the past 9 ka from the annually laminated sedimentary sequence of Lake
Xiaolongwan, northeastern China. The n-alkane distribution suggests that
Lake Xiaolongwan has undergone a shift from an oligotrophic state with
low algal production and little emergent/submerged macrophytes in the
early Holocene, to a eutrophic state with high algal production and
abundant emergent/submerged macrophytes since the middle Holocene. The
pattern of variation observed in the biomarker proxies ACL (the n-alkane
average chain length), Paq (aquatic macrophyte versus aquatic
macrophyte and terrestrial plant ratio), and LPTP (lake
productivity/terrigenous organic production) is throughout the record
similar to that of the total organic carbon. The variation of
compound-specific carbon isotopic values in the middle- and short-chain
alkanes was mainly regulated by lake productivity and the accumulating
organic pool through time. In this forested region, where the vegetation
is dominated by C3 plants, the long-chain n-alkanes (C27-C31) are
predominantly derived from leaf wax lipids. The compound-specific
δ13C27-31 value is sensitive to effective precipitation, and therefore
represents a useful indicator of regional monsoonal precipitation.
Spectral analysis on the δ13C27-31 time series reveals significant
periodicities of 87-89, 205-212, 1020-1050 and 1750-2041 years. On the
centennial timescale, the quasi-periodicities around 88 and 210 years
suggest a strong link between solar activity and monsoon rainfall. The
millennial monsoon cycle in northeastern China is associated with sea
surface temperature (SST) variations in two active centers of the summer
monsoon, the western Pacific Subtropical High (WPSH) and the Okhotsk
High. Increasing SST in the subtropical sea may cause a northwards shift
of the WPSH, which extends the monsoon rain band (Meiyu) to
northeastern China, and thus increasing rainfall in that region.
Meanwhile, decreasing SST in the Okhotsk Sea may strengthen the Okhotsk
high, bringing more moisture into northeastern China. We suggest that
the Pacific Ocean is a main regulator for summer monsoon rainfall in
northeastern China at present and at different time scales during the
Holocene.
Quasi-biennial oscillation and solar cycle influences on winter Arctic total ozone
Li and Tung 2014 Journal of Geophysical Research: Atmospheres 119, 5823-5835
The total column ozone (TCO) observed from satellites and assimilated in
the European Centre for Medium-Range Weather Forecasts since 1979 is
used as an atmospheric tracer to study the modulations of the winter
Arctic stratosphere by the quasi-biennial oscillation (QBO) and the
solar cycle. It is found that both the QBO and solar forcings in low
latitudes can perturb the late winter polar vortex, likely via planetary
wave divergence, causing an early breakdown of the vortex in the form
of sudden stratospheric warming. As a result, TCO within the vortex in
late winter can increase by ˜60 Dobson unit during either a solar
maximum or an easterly phase of the QBO, or both, relative to the least
perturbed state when the solar cycle is minimum and the QBO is in the
westerly phase. In addition, from the solar maximum to the solar minimum
during the QBO easterly phase, the change in TCO is found to be
statistically insignificant. Therefore, the "reversal" of the Holton-Tan
effect, reported in some previous studies using lower stratospheric
temperature, is not evident in the TCO behavior of both observation and
assimilation.
Solar forcing of Nile discharge and sapropel S1 formation in the early to middle Holocene eastern Mediterranean
Hennekam et al. 2014 Paleoceanography 29, 343-356
We present high-resolution records for oxygen isotopes of the planktic
foraminifer Globigerinoides ruber (d18Oruber) and bulk sediment
inorganic geochemistry for Holocene-age sediments from the southeast
Mediterranean. Our d18Oruber record appears to be dominated by Nile
discharge rather than basin-scale salinity/temperature changes. Nile
discharge was enhanced in the early to middle Holocene relative to
today. The timing of the long-term maximum in Nile discharge during the
early Holocene corresponds to the timing of maximum intensity of the
Indian Ocean-influenced Southwest Indian summer monsoon (SIM). This
coincidence suggests a major influence of an Indian Ocean moisture
source on Nile discharge in the early to middle Holocene, while,
presently, the Atlantic Ocean is the main moisture source. Nile
discharge was highly variable on multicentennial time scale during the
early to middle Holocene, being strongly influenced by variable solar
activity. This solar-driven variability is also recorded in
contemporaneous SIM records, however, not observed in an Atlantic
Ocean-derived West African summer monsoon record from the Holocene. This
supports the hypothesis that the Indian Ocean moisture source
predominantly controlled Nile discharge at that time. Solar-driven
variability in Nile discharge also influenced paleoenvironmental
conditions in the eastern Mediterranean. Bulk sediment Ba/Al and V/Al,
used as indicators for (export) productivity and redox conditions,
respectively, varied both in response to solar forcing on
multicentennial time scales. We suggest that changes in Nile discharge
on these time scales have been concordant with nutrient inputs to, and
shallow ventilation of, the eastern Mediterranean.
Solar-wind-driven geopotential height anomalies originate in the Antarctic lower troposphere
Lam et al. 2014 Geophysical Research Letters
We use NCEP/NCAR reanalysis data to estimate the altitude and timelag
dependence of the correlation between the interplanetary magnetic field
component, By, and the geopotential height anomaly above Antarctica. The
correlation is most statistically significant within the troposphere.
The peak in the correlation occurs at greater timelags at the tropopause
(c. 6-8 days) and in the mid-troposphere (c. 4 days), than in the lower
troposphere (c. 1 day). This supports a mechanism involving the action
of the global atmospheric electric circuit, modified by variations in
the solar wind, on lower tropospheric clouds. The increase in timelag
with increasing altitude is consistent with the upward propagation by
conventional atmospheric processes of the solar-wind-induced variability
in the lower troposphere. This is in contrast to the downward
propagation of atmospheric effects to the lower troposphere from the
stratosphere due to solar-variability-driven mechanisms involving
ultra-violet radiation or energetic particle precipitation.
Is a sudden increase of irregularity of sunspot numbers a precursor of a return to low solar activity?
Shapoval et al. 2014 Journal of Geophysical Research - Space Physics
We have recently introduced an irregularity index λ for daily sunspot
numbers International Sunspot Number (ISSN), derived from the well-known
Lyapunov exponent, that attempts to reflect irregularities in the
chaotic process of solar activity. Like the Lyapunov exponent, the
irregularity index is computed from the data for different embedding
dimensions m (2-32). When m = 2, λ maxima match ISSN maxima of the
Schwabe cycle, whereas when m = 3, λ maxima occur at ISSN minima. The
patterns of λ as a function of time remain similar from m = 4 to 16: the
dynamics of λ change between 1915 and 1935, separating two regimes, one
from 1850 to 1915 and the other from 1935 to 2005, in which λ retains a
similar structure. A sharp peak occurs at the time of the ISSN minimum
between cycles 23 and 24, possibly a precursor of unusual cycle 24 and
maybe a new regime change; λ is significantly smaller during the
ascending and descending phases of solar cycles. Differences in values
of the irregularity index observed for different cycles reflect
differences in correlations in sunspot series at a scale much less than
the 4 year sliding window used in computing them; the lifetime of
sunspots provides a source of correlation at that time scale. The burst
of short-term irregularity evidenced by the strong λ peak at the minimum
of cycles 23 and 24 would reflect a decrease in correlation at the time
scale of several days rather than a change in the shape of the cycle.
Natural variability, radiative forcing and climate response in the recent hiatus reconciled
Huber and Knutti 2014 Nature Geoscience 7, 651-656
Global mean surface warming over the past 15 years or so has been less
than in earlier decades and than simulated by most climate models.
Natural variability, a reduced radiative forcing, a smaller warming
response to atmospheric carbon dioxide concentrations8, 9 and coverage
bias in the observations10 have been identified as potential causes.
However, the explanations of the so-called 'warming hiatus' remain
fragmented and the implications for long-term temperature projections
are unclear. Here we estimate the contribution of internal variability
associated with the El Niño/Southern Oscillation (ENSO) using segments
of unforced climate model control simulations that match the observed
climate variability. We find that ENSO variability analogous to that
between 1997 or 1998 and 2012 leads to a cooling trend of about -0.06
°C. In addition, updated solar and stratospheric aerosol forcings from
observations explain a cooling trend of similar magnitude (-0.07 °C).
Accounting for these adjusted trends we show that a climate model of
reduced complexity with a transient climate response of about 1.8 °C is
consistent with the temperature record of the past 15 years, as is the
ensemble mean of the models in the Coupled Model Intercomparison Project
Phase 5 (CMIP5). We conclude that there is little evidence for a
systematic overestimation of the temperature response to increasing
atmospheric CO2 concentrations in the CMIP5 ensemble.
Indian summer monsoon rainfall: Dancing with the tunes of the sun
Hiremath et al. 2014 New Astronomy
There is strong statistical evidence that solar activity influences the
Indian summer monsoon rainfall. To search for a physical link between
the two, we consider the coupled cloud hydrodynamic equations, and
derive an equation for the rate of precipitation that is similar to the
equation of a forced harmonic oscillator, with cloud and rain water
mixing ratios as forcing variables. Those internal forcing variables are
parameterized in terms of the combined effect of external forcing as
measured by sunspot and coronal hole activities with several well known
solar periods (9, 13 and 27 days; 1.3, 5, 11 and 22 years). The equation
is then numerically solved and the results show that the variability of
the simulated rate of precipitation captures very well the actual
variability of the Indian monsoon rainfall, yielding vital clues for a
physical understanding that has so far eluded analyses based on
statistical correlations alone. We also solved the precipitation
equation by allowing for the effects of long-term variation of aerosols.
We tentatively conclude that the net effects of aerosols variation are
small, when compared to the solar factors, in terms of explaining the
observed rainfall variability covering the full Indian monsoonal
geographical domains.
Persistent link between solar activity and Greenland climate during the Last Glacial Maximum
Adolphi et al. 2014 Nature Geoscience
Changes in solar activity have previously been proposed to cause
decadal- to millennial-scale fluctuations in both the modern and
Holocene climates1. Direct observational records of solar activity, such
as sunspot numbers, exist for only the past few hundred years, so solar
variability for earlier periods is typically reconstructed from
measurements of cosmogenic radionuclides such as 10Be and 14C from ice
cores and tree rings. Here we present a high-resolution 10Be record from
the ice core collected from central Greenland by the Greenland Ice Core
Project (GRIP). The record spans from 22,500 to 10,000 years ago, and
is based on new and compiled data. Using 14C records to control for
climate-related influences on 10Be deposition, we reconstruct centennial
changes in solar activity. We find that during the Last Glacial
Maximum, solar minima correlate with more negative d18O values of ice
and are accompanied by increased snow accumulation and sea-salt input
over central Greenland. We suggest that solar minima could have induced
changes in the stratosphere that favour the development of high-pressure
blocking systems located to the south of Greenland, as has been found
in observations and model simulations for recent climate. We conclude
that the mechanism behind solar forcing of regional climate change may
have been similar under both modern and Last Glacial Maximum climate
conditions.
Rotation of the Earth, solar activity and cosmic ray intensity
Barlyaeva et al. 2014 Ann. Geophys. 32, 761-771
We analyse phase lags between the 11-year variations of three records:
the semi-annual oscillation of the length of day (LOD), the solar
activity (SA) and the cosmic ray intensity (CRI). The analysis was done
for solar cycles 20-23. Observed relationships between LOD, CRI and SA
are discussed separately for even and odd solar cycles. Phase lags were
calculated using different methods (comparison of maximal points of
cycles, maximal correlation coefficient, line of synchronization of
cross-recurrence plots). We have found different phase lags between SA
and CRI for even and odd solar cycles, confirming previous studies. The
evolution of phase lags between SA and LOD as well as between CRI and
LOD shows a positive trend with additional variations of phase lag
values. For solar cycle 20, phase lags between SA and CRI, between SA
and LOD, and between CRI and LOD were found to be negative. Overall, our
study suggests that, if anything, the length of day could be influenced
by solar irradiance rather than by cosmic rays.
On the detection of the solar signal in the tropical stratosphere
Chiodo et al. 2014 Atmos. Chem. Phys. 14, 5251-5269
We investigate the relative role of volcanic eruptions, El Niño-Southern
Oscillation (ENSO), and the quasi-biennial oscillation (QBO) in the
quasi-decadal signal in the tropical stratosphere with regard to
temperature and ozone commonly attributed to the 11 yr solar cycle. For
this purpose, we perform transient simulations with the Whole Atmosphere
Community Climate Model forced from 1960 to 2004 with an 11 yr solar
cycle in irradiance and different combinations of other forcings. An
improved multiple linear regression technique is used to diagnose the 11
yr solar signal in the simulations. One set of simulations includes all
observed forcings, and is thereby aimed at closely reproducing
observations. Three idealized sets exclude ENSO variability, volcanic
aerosol forcing, and QBO in tropical stratospheric winds, respectively.
Differences in the derived solar response in the tropical stratosphere
in the four sets quantify the impact of ENSO, volcanic events and the
QBO in attributing quasi-decadal changes to the solar cycle in the model
simulations. The novel regression approach shows that most of the
apparent solar-induced lower-stratospheric temperature and ozone
increase diagnosed in the simulations with all observed forcings is due
to two major volcanic eruptions (i.e., El Chichon in 1982 and Mt.
Pinatubo in 1991). This is caused by the alignment of these eruptions
with periods of high solar activity. While it is feasible to detect a
robust solar signal in the middle and upper tropical stratosphere, this
is not the case in the tropical lower stratosphere, at least in a 45 yr
simulation. The present results suggest that in the tropical lower
stratosphere, the portion of decadal variability that can be
unambiguously linked to the solar cycle may be smaller than previously
thought.
Study of the influence of solar variability on a regional (Indian) climate: 1901-2007
Aslam and Badruddin 2014 Advances in Space Research
We use Indian temperature data of more than 100 years to study the
influence of solar activity on climate. We study the Sun-climate
relationship by averaging solar and climate data at various time scales;
decadal, solar activity and solar magnetic cycles. We also consider the
minimum and maximum values of sunspot number (SSN) during each solar
cycle. This parameter SSN is correlated better with Indian temperature
when these data are averaged over solar magnetic polarity epochs (SSN
maximum to maximum). Our results indicate that the solar variability may
still be contributing to ongoing climate change and suggest for more
investigations.
Solar control on the cloud liquid water content and integrated water vapor associated with monsoon rainfall over India
Maitra et al. 2014 Journal of Atmospheric and Solar-Terrestrial Physics
A long-term observation over three solar cycles indicates a perceptible
influence of solar activity on rainfall and associated parameters in the
Indian region. This paper attempts to reveal the solar control on the
cloud liquid water content (LWC) and integrated water vapor (IWV) along
with Indian Summer Monsoon (ISM) rainfall during the period of 1977-2012
over nine different Indian stations. Cloud LWC and IWV are positively
correlated with each other. An anti-correlation is observed between the
Sunspot Number (SSN) and ISM rainfall for a majority of the stations and
a poor positive correlation obtained for other locations. Cloud LWC and
IWV possess positive correlations with Galactic Cosmic Rays (GCR) and
SSN respectively for most of the stations. The wavelet analyses of SSN,
ISM rainfall, cloud LWC and IWV have been performed to investigate the
periodic characteristics of climatic parameters and also to indicate the
varying relationship of solar activity with ISM rainfall, cloud LWC and
IWV. SSN, ISM rainfall and IWV are found to have a peak at around 10.3
years whereas a dip is observed at that particular period for cloud LWC.
Reconstruction and prediction of the total solar irradiance: From the Medieval Warm Period to the 21st century
Herrera et al. 2014 New Astronomy 34, 221-233
Total solar irradiance is the primary energy source of the Earth's
climate system and therefore its variations can contribute to natural
climate change. This variability is characterized by, among other
manifestations, decadal and secular oscillations, which has led to
several attempts to estimate future solar activity. Of particular
interest now is the fact that the behavior of the solar cycle 23 minimum
has shown an activity decline not previously seen in past cycles for
which spatial observations exist: this could be signaling the start of a
new grand solar minimum. The estimation of solar activity for the next
hundred years is one of the current problems in solar physics because
the possible occurrence of a future grand solar minimum will probably
have an impact on the Earth's climate. In this study, using the PMOD and
ACRIM TSI composites, we have attempted to estimate the TSI index from
year 1000 AD to 2100 AD based on the Least Squares Support Vector
Machines, which is applied here for the first time to estimate a solar
index. Using the wavelet transform, we analyzed the behavior of the
total solar irradiance time series before and after the solar grand
minima. Depending on the composite used, PMOD (or ACRIM), we found a
grand minimum for the 21st century, starting in c. 2004c. 2004 (or 2002)
and ending in c. 2075c. 2075 (or 2063), with an average irradiance of
1365.5 (or 1360.5) Wm-2+-1sd=0.3Wm-2+-1sd=0.3 (or 0.9) Wm-2Wm-2.
Moreover, we calculated an average radiative forcing between the present
and the 21st century minima of c. -0.1c. -0.1 (or -0.2) Wm-2Wm-2, with
an uncertainty range of -0.04-0.04 to -0.14-0.14 (or -0.12-0.12 to
-0.33-0.33) Wm-2Wm-2. As an indicator of the TSI level, we calculated
its annual power anomalies; in particular, future solar cycles from 24
to 29 have lower power anomalies compared to the present, for both
models. We also found that the solar activity grand minima periodicity
is of 120 years; this periodicity could possibly be one of the principal
periodicities of the magnetic solar activity not so previously well
recognized. The negative (positive) 120-year phase coincides with the
grand minima (maxima) of the 11-year periodicity.
Solar cycle effects on Indian summer monsoon dynamics
Ratnam et al. 2014 Journal of Atmospheric and Solar-Terrestrial Physics
Solar activity associated with sunspot number influences the atmospheric
circulation on various time scales. As Indian summer monsoon (ISM) is
the manifestation between warmer Asian continent and the cooler Indian
Ocean, changes in the solar cycle are expected to influence the ISM
characteristics. Among several elements of ISM, Tropical Easterly Jet
(TEJ), Low Level Jet (LLJ), and rainfall are important features. As a
part of CAWSES India Phase II theme 1 (solar influence on climate (0-100
km)) programme, we made an attempt to investigate the role of solar
cycle variability on these ISM features using long-term data available
from NECP/NCAR (1948-2010) and ERA-Interim (1979-2010) re-analysis
products. To check the suitability of these data sets, ground based
observations available over the Indian region are also considered. ISM
characteristics are studied separately for the maximum and minimum as
well as increasing and decreasing solar cycle conditions. Amplitudes
corresponding to the solar cycle observed in TEJ, LLJ and rainfall are
extracted using advanced statistical tool known as intrinsic mode
function. Long-term trends in TEJ reveal decreasing trend at the rate of
0.13 m/s/yr (between 1948 and 2000) and no perceptible trend in LLJ.
There exists inverse relation between TEJ strength and Central India
rainfall. Large difference of 2 m/s (5 m/s) in the zonal winds of TEJ
between solar maximum and minimum (increasing and decreasing trend) is
noticed. There exists a difference of c. 2 m/s in LLJ winds between
solar maximum and minimum and increasing and decreasing trend of the
solar cycle. However, no consistent relation between the ISM rainfall
and solar cycle is noticed over Indian region unlike reported earlier
but there exists a delayed effect around 13 years. We attribute the
observed features as linear and non-linear relation between dynamics of
ISM, rainfall and solar cycle, respectively.
Diurnal tide in the low-latitude troposphere and stratosphere: Long-term trends and role of the extended solar minimum
Ratnam et al. 2014 Journal of Atmospheric and Solar-Terrestrial Physics
In the present study, long-term trends in the diurnal tide in the
troposphere and stratosphere over a tropical station Gadanki (13.5 N,
79.2 E) are investigated using ERA-Interim wind and temperature products
available since 1979. Suitability of the ERA-Interim data for the
present study is ascertained using simultaneous radiosonde and MST radar
observations over Gadanki and good consistency was found between the
two. In general, diurnal tide amplitudes are found to increase from
troposphere to stratosphere, as expected. Amplitude of the diurnal tide
shows a long-term linear increasing trend, which becomes prominent in
the stratosphere. Interestingly, convection over Gadanki also exhibits
an increasing trend suggesting that they are related. Role of solar
cycle on the diurnal tide is investigated by separating the tidal
amplitudes during minimum and maximum of solar cycles 21, 22 and 23.
Significantly higher amplitudes in the recent extended solar minimum are
noticed though no consistent relation is found between solar activity
and tides, in general. These results are discussed in the light of role
of convection on the generation of the diurnal tide and their
propagation to the higher altitudes, coupling lower and middle
atmospheres. Special emphasis is made on the observed large amplitudes
of the diurnal tide in the extended solar minimum while relating the
observed changes to the background circulation.
Reconstructing the Holocene geomagnetic field
Korte et al. 2011 Earth and Planetary Science Letters 312, 497-505
Knowledge of the Holocene evolution of Earth's magnetic field is
important for understanding geodynamo processes in the core, is
necessary for studying long-term solar-terrestrial relationships, and
can provide useful age constraints for archeologicaland stratigraphic
applications. Continuous time-varying global field models based on
archeo- and paleomagnetic data are useful tools in this regard. We use a
comprehensive data compilation and recently refined modelling
strategies to produce CALS10k.1b, the first time-varying spherical
harmonic geomagnetic field model spanning 10 ky. The model is an average
obtained from bootstrap sampling to take account of uncertainties in
magnetic components and ages in the data (and hence has version number
1b instead of 1). This model shows less spatial and temporal resolution
than earlier versions for 0-3 ka, and particularly aims to provide a
robust representation of the large-scale field at the core-mantle
boundary (CMB). We discuss the geomagnetic dipole evolution and changes
in Holocene magnetic field morphology at the CMB as shown by the new
reconstruction. The results are compatible with earlier models (CALS3k.3
and CALS3k.4) for 0-3 ka, but reveal some clear deficiencies in the 0-7
ka CALS7K.2 model prior to 3 ka. CALS10k.1b is able to resolve mobile
and structurally-evolving high latitude radial field flux lobes at the
CMB in both hemispheres, as well as persistent non-zonal structure, in
the 10 ky average. Contributions to the average field from time-varying
structures in the equatorial Indonesian-Australian region are
particularly striking.
Investigations of temporal changes in climate and the geomagnetic field via high-resolution radiocarbon dating
Mellström, 2014 PhD thesis, Lund University
Geological archives have shown periods of abrupt climate change in the
relatively stable Holocene epoch (last ca. 11 700 years). One of these
periods was around 2800 cal BP. Several records, mainly from Europe,
reveal a shift towards wetter, cooler and windier conditions. There are,
however, indications for a global extent of the climate change. The
climate change coincides with a distinct increase in the atmospheric
radiocarbon (14C) concentration, which has been interpreted to be a
result of decreased solar activity. Therefore, a solar-induced climate
change has been suggested. In addition to changes in solar activity,
geomagnetic field records also show prominent variations around
3000-2000 cal BP. In order to investigate the temporal... [see url for
more of the abstract]
Stationarity of extreme bursts in the solar wind
Moloney and Davidsen 2014 Physical Review E
Recent results have suggested that the statistics of bursts in the solar
wind vary with solar cycle. Here, we show that this variation is
basically absent if one considers extreme bursts. These are defined as
threshold-exceeding events over the range of high thresholds for which
their number decays as a power law. In particular, we find that the
distribution of duration times and energies of extreme bursts in the
solar wind e parameter and similar observables are
independent of the solar cycle and in this sense stationary, and show
robust asymptotic power laws with exponents that are independent of the
specific threshold. This is consistent with what has been observed for
solar flares and, thus, provides evidence in favor of a link between
solar flares and extreme bursts in the solar wind.
Spatial distribution of northern hemisphere temperatures during different phases of the solar cycle
Maliniemi et al 2014 Journal of Geophysical Research: Atmospheres
Several recent studies have found variability in the Northern Hemisphere
winter climate related to different parameters of solar activity. While
these results consistently indicate some kind of solar modulation of
tropospheric and stratospheric circulation and surface temperature,
opinions on the exact mechanism and the solar driver differ. Proposed
drivers include, e.g., total solar irradiance (TSI), solar UV radiation,
galactic cosmic rays and magnetospheric energetic particles. While some
of these drivers are difficult to distinguish because of their closely
similar variation over the solar cycle, other suggested drivers have
clear differences in their solar cycle evolution. For example,
geomagnetic activity and magnetospheric particle fluxes peak in the
declining phase of the sunspot cycle, in difference to TSI and UV
radiation which more closely follow sunspots. Using 13 solar cycles
(1869-2009) we study winter surface temperatures and North Atlantic
oscillation (NAO) during four different phases of the sunspot cycle:
minimum, ascending, maximum and declining phase. We find significant
differences in the temperature patterns between the four cycle phases,
which indicates a solar cycle modulation of winter surface temperatures.
However, the clearest pattern of the temperature anomalies is not found
during sunspot maximum or minimum, but during the declining phase, when
the temperature pattern closely resembles the pattern found during
positive NAO. Moreover, we find the same pattern during the low sunspot
activity cycles of 100 years ago, suggesting that the pattern is largely
independent of the overall level of solar activity.
Galactic cosmic rays flux and geomagnetic activity coupling with cloud covering in Abastumani
Todua and Didebulidze 2013 Journal of the Georgian Geophysical Society, Issue B. Physics of Atmosphere, Ocean and Space Plasma, v.16b, 2013, pp 82-88
The analysis of long-term observations in Abastumani (41.75 N, 42.82 E)
revealed differences in the seasonal variations of Galactic Cosmic Rays
(GCRs) flux and geomagnetic activities at cloudless days and cloudless
nights. Particularly, in summer, the inter-annual distributions of the
planetary geomagnetic Ap index and Sudden Storm Commencement (SSC)
exhibited minima for cloudless days and maxima for cloudless nights,
where GCR flux showed deep minimum. This feature in the case of SSC was
demonstrated for the first time. The long-term trends of Ap index during
summer time also revealed various meanings for cloudless day and night.
These results can be regarded as the effect of cosmic factors on cloud
covering in Abastumani, which in turn may have an influence on climatic
variations.
A 2700 cal yr BP extreme flood event revealed by sediment accumulation in Amazon floodplains
Moreira-Turcq et al. in press Palaeogeography, Palaeoclimatology, Palaeoecology
Climatic conditions are one of the most important factors affecting
hydrological processes in fluvial systems. Higher discharges are
responsible for higher erosion, greater transport, and also higher
deposition. Consequently, sediment accumulation in Amazonia floodplain
river-connected lakes can be directly related to hydrological patterns
of the Amazon River mainstream. In this context, we analyzed five
sediment cores taken in two floodplain systems situated in the lower
Amazon River, to investigate sediment accumulation patterns during the
Holocene. Our records show abrupt fluctuations in sedimentation rates in
lakes that can reach more than 2 cm/yr during some periods. We find
that in all cores, sediment stratigraphy is characterized by packages of
sediments of uniform age, which are typically 10-80 cm thick and
present a variegated color. The 14C age of the upper package is about
2700 cal yr BP. During this abrupt event, sediment accumulation rates in
floodplain lakes can be at least 200 times higher than those of
"normal" periods. This sedimentation event is interpreted as being the
consequence of one or several successive extreme floods. The 2700 cal yr
BP event has been also observed in other sites in South America and
other regions in the world, although different impacts can be observed
in each system. This event probably corresponds to a conjunction of
favorable conditions for extreme Amazon discharge associated with the
Middle to Late Holocene increase of austral summer insolation and shifts
of the Intertropical Convergence Zone (ITCZ) from northern to southern
positions. In this context, a marked negative peak in solar irradiance
at 2700 cal yrs BP seems to have provoked cooling on the continents and a
southward shift of the ITCZ associated with a probable reduction in
Atlantic Meridian Overturning Circulation.
A History of Solar Activity over Millennia
Usoskin, 2008/2010/2013 [updated] Living Reviews in Solar Physics
Presented here is a review of present knowledge of the long-term
behavior of solar activity on a multi-millennial timescale, as
reconstructed using the indirect proxy method. The concept of solar
activity is discussed along with an overview of the special indices used
to quantify different aspects of variable solar activity, with special
emphasis upon sunspot number. Over long timescales, quantitative
information about past solar activity can only be obtained using a
method based upon indirect proxy, such as the cosmogenic isotopes 14C
and 10Be in natural stratified archives (e.g., tree rings or ice cores).
We give an historical overview of the development of the proxy-based
method for past solar-activity reconstruction over millennia, as well as
a description of the modern state. Special attention is paid to the
verification and cross-calibration of reconstructions. It is argued that
this method of cosmogenic isotopes makes a solid basis for studies of
solar variability in the past on a long timescale (centuries to
millennia) during the Holocene. A separate section is devoted to
reconstructions of strong solar-energetic-particle (SEP) events in the
past, that suggest that the present-day average SEP flux is broadly
consistent with estimates on longer timescales, and that the occurrence
of extra-strong events is unlikely. Finally, the main features of the
long-term evolution of solar magnetic activity, including the statistics
of grand minima and maxima occurrence, are summarized and their
possible implications, especially for solar/stellar dynamo theory, are
discussed.
On the relationship between global land-ocean temperature and various descriptors of solar-geomagnetic activity and climate
Wilson 2014 NASA Technical Report, 62p
Examined are sunspot cycle- (SC-) length averages of the annual
January-December values of the Global Land-Ocean Temperature Index
(GLOTI) in relation to SC-length averages of annual values of various
descriptors of solar-geomagnetic activity and climate, incorporating
lags of 0-5 yr. For the overall interval SC12-SC23, the GLOTI is
inferred to correlate best against the parameter aa(I:SSN) incorporating
lag = 5 yr, where the parameter aa(I:SSN) refers to the resultant aa
value having removed that portion of the annual aa average value due to
the yearly variation of sunspot number (SSN). The inferred correlation
between the GLOTI and aa(I:SSN) is statistically important at confidence
level cl >99.9%, having a coefficient of linear correlation r =
0.865 and standard error of estimate se = 0.149 degC. Excluding the most
recent cycles SC22 and SC23, the inferred correlation is stronger,
having r = 0.969 and se = 0.048 degC. With respect to the overall trend
in the GLOTI, which has been upwards towards warmer temperatures since
SC12 (1878-1888), solar-geomagnetic activity parameters are now trending
downwards (since SC19). For SC20-SC23, in contrast, comparison of the
GLOTI against SC-length averages of the annual value of the Mauna Loa
carbon dioxide (MLCO2>) index is found to be highly statistically
important (cl >> 99.9%), having r = 0.9994 and se = 0.012 degC for
lag = 2 yr. On the basis of the inferred preferential linear
correlation between the GLOTI and MLCO2, the current ongoing SC24 is
inferred to have GLOTI warmer than was seen in SC23 (i.e., >0.526
degC), probably in excess of 0.68 degC (relative to the 1951-1980 base
period).
The asymmetry of the climate system's response to solar forcing changes and its implications for geoengineering scenarios
Schaller et al. 2014 Journal of Geophysical Research - Atmospheres
Motivated by proposals to compensate CO2-induced warming with a decrease
in solar radiation, this study investigates how single-forcing
simulations should be combined to best represent the spatial patterns of
surface temperature and precipitation of idealized geoengineering
scenarios. Using instantaneous and transient simulations with changing
CO2 and solar forcings, we show that a geoengineering scenario, i.e., a
scenario where the solar constant is reduced as CO2 concentrations are
increased, is better represented by subtracting the response pattern of a
solar forcing increase simulation from the response pattern of a CO2
forcing increase simulation, than by adding the response pattern of a
solar forcing decrease simulation to a CO2 forcing increase simulation.
The reason is a asymmetric response of the climate system to a forcing
increase or decrease between both hemispheres. In particular, the
Atlantic meridional overturning circulation responds faster to a solar
forcing decrease compared to a solar forcing increase. Further, the
climate feedbacks are state and region dependent, which is particularly
apparent in the polar regions due to the sea ice-albedo feedback. The
importance of understanding the local response of the climate system to
geoengineering and single-forcing scenarios is highlighted, since these
aspects are hardly discernible when only global mean values are
considered.
Forcings and feedbacks in the GeoMIP ensemble for a reduction in solar irradiance and increase in CO2
Huneeus et al. 2014 Journal of Geophysical Research - Atmospheres
The effective radiative forcings (including rapid adjustments) and
feedbacks associated with an instantaneous quadrupling of the
preindustrial CO2 concentration and a counterbalancing reduction of the
solar constant are investigated in the context of the Geoengineering
Model Intercomparison Project (GeoMIP). The forcing and feedback
parameters of the net energy flux, as well as its different components
at the top-of-atmosphere (TOA) and surface, were examined in 10 Earth
System Models to better understand the impact of solar radiation
management on the energy budget. In spite of their very different
nature, the feedback parameter and its components at the TOA and surface
are almost identical for the two forcing mechanisms, not only in the
global mean but also in their geographical distributions. This
conclusion holds for each of the individual models despite intermodel
differences in how feedbacks affect the energy budget. This indicates
that the climate sensitivity parameter is independent of the forcing
(when measured as an effective radiative forcing). We also show the
existence of a large contribution of the cloudy-sky component to the
shortwave effective radiative forcing at the TOA suggesting rapid cloud
adjustments to a change in solar irradiance. In addition, the models
present significant diversity in the spatial distribution of the
shortwave feedback parameter in cloudy regions, indicating persistent
uncertainties in cloud feedback mechanisms.
Mid- to Late-Holocene AustralianeIndonesian summer monsoon variability
Steinke et al. 2014 Quaternary Science Reviews 93, 142-154
The Australian-Indonesian monsoon has a governing influence on the
agricultural practices and livelihood in the highly populated islands of
Indonesia. However, little is known about the factors that have
influenced past monsoon activity in southern Indonesia. Here, we present
a c. 6000 years high-resolution record of Australian-Indonesian summer
monsoon (AISM) rainfall variations based on bulk sediment element
analysis in a sediment archive retrieved offshore northwest Sumba Island
(Indonesia). The record suggests lower riverine detrital supply and
hence weaker AISM rainfall between c. 6000 yr BP and 3000 yr BP compared
to the Late Holocene. We find a distinct shift in terrigenous sediment
supply at around 2800 yr BP indicating a reorganization of the AISM from
a drier Mid Holocene to a wetter Late Holocene in southern Indonesia.
The abrupt increase in rainfall at around 2800 yr BP coincides with a
grand solar minimum. An increase in southern Indonesian rainfall in
response to a solar minimum is consistent with climate model simulations
that provide a possible explanation of the underlying mechanism
responsible for the monsoonal shift. We conclude that variations in
solar activity play a significant role in monsoonal rainfall variability
at multi-decadal and longer timescales. The combined effect of orbital
and solar forcing explains important details in the temporal evolution
of AISM rainfall during the last 6000 years. By contrast, we find
neither evidence for volcanic forcing of AISM variability nor for a
control by long-term variations in the El Ninho-Southern Oscillation
(ENSO).
Imprint of long-term solar signal in groundwater recharge fluctuation rates from Northwest China
Tiwari and Rajesh 2014 Geophysical Research Letters
Multiple spectral and statistical analyses of a 700 yearlong temporal
record of groundwater recharge from the dry lands, Badain Jaran Desert
(Inner Mongolia) of Northwest China reveal a stationary harmonic cycle
at ~200 +- 20 year. Interestingly, the underlying periodicity in
groundwater recharge fluctuations is similar to those of solar-induced
climate cycle "Suess wiggles" and appears to be coherent with phases of
the climate fluctuations and solar cycles. Matching periodicity of
groundwater recharge rates and solar and climate cycles renders a strong
impression that solar-induced climate signals may act as a critical
amplifier for driving the underlying hydrographic cycle through the
common coupling of long-term Sun-climate groundwater linkages.
Sunspot cycles recorded in Mesoproterozoic carbonate biolaminites
Tang et al. 2014 Precambian Research
Well-preserved carbonate biolaminites from the early Mesoproterozoic
Wumishan Formation (ca. 1.5-1.45 Ga) of North China show
submillimeter-scale yearly couplets that consist of alternating dark and
light laminae, and are texturally similar to those reported from
Holocene tufas. Power spectrum and wavelet transform analyses of laminar
couplet thickness variations and geochemical series (Ca, Fe, Co/Ti,
Cr/Ti, and Br) reveal a prominent periodicity at 9.0-11.7 and a less
prominent periodicity at 19.7-21.4 couplets. These coherent periodic
modes match well with the 11-yr Schwabe sunspot cycle and 22-yr solar
Hale cycle. The observed layering pattern is thus interpreted as
recording solar induced climate changes that may have modulated
microbial growth rate and biomass production in restricted subtidal
environments on a broad epicontinental platform. The documented example
represents the first reported solar signature in Mesoproterozoic marine
carbonates and implies the sensitivity of microbial life to
environmental changes prior to metazoan evolution.
Response of the Bering Sea to 11-year solar irradiance cycles during the Bølling-Allerød
Katsuki et al. 2014 Geophysical Research Letters
Previous studies find decadal climate variability possibly related to
solar activity, although the details regarding the feedback with the
ocean environment and ecosystem remain unknown. Here, we explore the
feedback system of solar irradiance change during the Bølling-Allerød
period, based on laminated sediments in the northern Bering Sea. During
this period, well-ventilated water was restricted to the upper
intermediate layer, and oxygen-poor lower intermediate water preserved
the laminated sediment. An 11-year cycle of diatom and radiolarian flux
peaks was identified from the laminated interval. Increased fresh
meltwater input and early sea-ice retreat in spring under the solar
irradiance maximum follow the positive phase of Arctic Oscillation which
impacted the primary production and volume of upper intermediate water
production in the following winter. Strength of this 11 year solar
irradiance effect might be further regulated by the pressure patterns of
Pacific decadal oscillation and/or El Niño-Southern Oscillation
variability.
Sensitivity of the surface temperature to changes in total solar irradiance calculated with the WRF model
Cipaguata et al. 2014 Geofisica Internacional 53
The temperature sensitivity of the WRF model to changes in Total Solar
Irradiance (TSI). The simulations were performed for a region centered
over the North Atlantic Ocean, including portions of Eastern North
America, Western Europe and Northwest Africa. Four simulations were run
with different TSI values. Also, a fifth simulation was performed in
which we varied the initial atmospheric conditions, in order to compare
the effect on the temperature of both, changes in the TSI and initial
atmospheric conditions. Comparing temperature monthly averages we found
that changes in TSI and in the initial conditions have a measurable
impact on temperature in the region of study. The sensitivity of the
model using non-dimensional parameters was also estimated. The numerical
experiments show some features that might allow to distinguish between
the effects on the temperature due to changes in TSI from those caused
by initial conditions. However, TSI changes are of the same order of
magnitude than those of disturbances in the initial conditions. We also
found that the mean monthly values of temperature over the full grid,
did not present significant variations due to changes of either initial
conditions or TSI.
Effect of solar variations on particle formation and cloud condensation nuclei
Yu anda Luo 2014 Environmental Research Letters 9, 045004
The impact of solar variations on particle formation and cloud
condensation nuclei (CCN), a critical step for one of the possible solar
indirect climate forcing pathways, is studied here with a global
aerosol model optimized for simulating detailed particle formation and
growth processes. The effect of temperature change in enhancing the
solar cycle CCN signal is investigated for the first time. Our global
simulations indicate that a decrease in ionization rate associated with
galactic cosmic ray flux change from solar minimum to solar maximum
reduces annual mean nucleation rates, number concentration of
condensation nuclei larger than 10 nm (CN10), and number concentrations
of CCN at water supersaturation ratio of 0.8% (CCN0.8) and 0.2% (CCN0.2)
in the lower troposphere by 6.8%, 1.36%, 0.74%, and 0.43%,
respectively. The inclusion of 0.2 C temperature increase enhances the
CCN solar cycle signals by around 50%. The annual mean solar cycle CCN
signals have large spatial and seasonal variations: (1) stronger in the
lower troposphere where warm clouds are formed, (2) about 50% larger in
the northern hemisphere than in the southern hemisphere, and (3) about a
factor of two larger during the corresponding hemispheric summer
seasons. The effect of solar cycle perturbation on CCN0.2 based on
present study is generally higher than those reported in several
previous studies, up to around one order of magnitude.
Seasonal temperature variability of the Neoglacial (3300-2500 BP) and Roman Warm Period (2500-1600 BP) reconstructed from oxygen isotope ratios of limpet shells (Patella vulgata), Northwest Scotland
Wang et al. 2012 Palaeogeography, Palaeoclimatology, Palaeoecology 317-318, 104-113
Seasonal sea-surface temperature variability for the Neoglacial
(3300-2500 BP) and Roman Warm Period (RWP; 2500-1600 BP), which
correspond to the Bronze and Iron Ages, respectively, was estimated
using oxygen isotope ratios obtained from high-resolution samples
micromilled from radiocarbon-dated, archaeological limpet (Patella
vulgata) shells. The coldest winter months recorded in Neoglacial shells
averaged 6.6 +- 0.3 C, and the warmest summer months averaged 14.7 +-
0.4 C. One Neoglacial shell captured a year without a summer, which may
have resulted from a dust veil from a volcanic eruption in the Katla
volcanic system in Iceland. RWP shells record average winter and summer
monthly temperatures of 6.3 +- 0.1 C and 13.3 +- 0.3 C, respectively.
These results capture a cooling transition from the Neoglacial to RWP,
which is further supported by earlier studies of pine history in
Scotland, pollen type analyses in northeast Scotland, and European
glacial events. The cooling transition observed at the boundary between
the Neoglacial and RWP in our study also agrees with the abrupt climate
deterioration at 2800-2700 BP (also referred to as the
Subboreal/Subatlantic transition) and therefore may have been driven by
decreased solar radiation and weakened North Atlantic Oscillation
conditions.
Ocean-atmosphere climate shift during the mid-to-late Holocene transition
Morley et al. 2014 Earth and Planetary Science Letters
Climate records of the mid-to-late Holocene transition, between 3-4
thousand years before present (ka), often exhibit a rapid change in
response to the gradual change in orbital insolation. Here we
investigate North Atlantic Central Water circulation as a possible
mechanism regulating the latitudinal temperature gradient (LTG), which,
in turn, amplifies climate sensitivity to small changes in solar
irradiance. Through this mechanism, sharp climate events and transitions
are the result of a positive feedback process that propagates and
amplifies climate events in the North Atlantic region. We explore these
linkages using an intermediate water temperature record reconstructed
from Mg/Ca measurements of benthic foraminifera (Hyalinea balthica) from
a sediment core off NW Africa (889 m depth) between 0 to 5.5 ka. Our
results show that Eastern North Atlantic Central Waters (ENACW) cooled
by c1 +- 0.7 C and densities decreased by dtheta = 0.4 +- 0.2 between
3.3 and 2.6 ka. This shift in ENACW hydrography illustrates a transition
towards enhanced mid-latitude atmospheric circulation after 2.7 ka in
particular during cold events of the late-Holocene. The presented
records demonstrate the important role of ENACW circulation in
propagating the climate signatures of the LTG by reducing the meridional
heat transfer from high to low latitudes during the transition from the
Holocene Thermal Maximum to the late-Holocene. In addition, the dynamic
response of ENACW circulation to the gradual climate forcing of LTGs
provides a prime example of an amplifying climate feedback mechanism.
Solar forcing of North Atlantic surface temperature and salinity over the past millennium
Moffa-Sánchez et al. 2014 Nature Geoscience
There were several centennial-scale fluctuations in the climate and
oceanography of the North Atlantic region over the past 1,000 years,
including a period of relative cooling from about AD 1450 to 1850 known
as the Little Ice Age. These variations may be linked to changes in
solar irradiance, amplified through feedbacks including the Atlantic
meridional overturning circulation. Changes in the return limb of the
Atlantic meridional overturning circulation are reflected in water
properties at the base of the mixed layer south of Iceland. Here we
reconstruct thermocline temperature and salinity in this region from AD
818 to 1780 using paired d18O and Mg/Ca ratio measurements of
foraminifer shells from a subdecadally resolved marine sediment core.
The reconstructed centennial-scale variations in hydrography correlate
with variability in total solar irradiance. We find a similar
correlation in a simulation of climate over the past 1,000 years. We
infer that the hydrographic changes probably reflect variability in the
strength of the subpolar gyre associated with changes in atmospheric
circulation. Specifically, in the simulation, low solar irradiance
promotes the development of frequent and persistent atmospheric blocking
events, in which a quasi-stationary high-pressure system in the eastern
North Atlantic modifies the flow of the westerly winds. We conclude
that this process could have contributed to the consecutive cold winters
documented in Europe during the Little Ice Age.
The Little Ice Age signature and subsequent warming seen in borehole temperature logs versus solar forcing model
Majorowicz et al. 2014 Int J Earth Sci
The 'low' in the transient temperature versus depth borehole profiles
around 120 m seen from deep temperature logs in the Canadian Prairies
(southern Alberta-southern Saskatchewan), as well as in some of the
European data, has been interpreted to be related to the Little Ice Age
(LIA). Data point to the lowest ground surface and subsurface
temperatures occurring in the very late eighteenth to nineteenth
centuries. Inversion of these logs shows that surface temperature lows
were followed by a recent warming period. Further, the synthetic
profiles built on the basis of solar forcing history, stretching as far
back as the beginning of the seventeenth century, suggest that the LIA
signatures interpreted from the inversion of the borehole temperature
logs would be difficult to be explained by known published models of
past solar irradiation despite large range of assumed sensitivities for
the couplings assumed, and that further forcing needs to be considered.
Evidence for external forcing of the Atlantic Multidecadal Oscillation since termination of the Little Ice Age
Knudsen et al. 2014 Nature Communications 5, 3323
The Atlantic Multidecadal Oscillation (AMO) represents a significant
driver of Northern Hemisphere climate, but the forcing mechanisms pacing
the AMO remain poorly understood. Here we use the available proxy
records to investigate the influence of solar and volcanic forcing on
the AMO over the last c. 450 years. The evidence suggests that external
forcing played a dominant role in pacing the AMO after termination of
the Little Ice Age (LIA; ca. 1400-1800), with an instantaneous impact on
mid-latitude sea-surface temperatures that spread across the North
Atlantic over the ensuing c.5 years. In contrast, the role of external
forcing was more ambiguous during the LIA. Our study further suggests
that the Atlantic Meridional Overturning Circulation is important for
linking external forcing with North Atlantic sea-surface temperatures, a
conjecture that reconciles two opposing theories concerning the origin
of the AMO.
The Impact of Different Absolute Solar Irradiance Values on Current Climate Model Simulations
Rind et al. 2013 J. Climate 27, 1100-1120
Simulations of the preindustrial and doubled CO2 climates are made with
the GISS Global Climate Middle Atmosphere Model 3 using two different
estimates of the absolute solar irradiance value: a higher value
measured by solar radiometers in the 1990s and a lower value measured
recently by the Solar Radiation and Climate Experiment. Each of the
model simulations is adjusted to achieve global energy balance; without
this adjustment the difference in irradiance produces a global
temperature change of 0.4°C, comparable to the cooling estimated for the
Maunder Minimum. The results indicate that by altering cloud cover the
model properly compensates for the different absolute solar irradiance
values on a global level when simulating both preindustrial and doubled
CO2 climates. On a regional level, the preindustrial climate simulations
and the patterns of change with doubled CO2 concentrations are again
remarkably similar, but there are some differences. Using a higher
absolute solar irradiance value and the requisite cloud cover affects
the model's depictions of high-latitude surface air temperature, sea
level pressure, and stratospheric ozone, as well as tropical
precipitation. In the climate change experiments it leads to an
underestimation of North Atlantic warming, reduced precipitation in the
tropical western Pacific, and smaller total ozone growth at high
northern latitudes. Although significant, these differences are
typically modest compared with the magnitude of the regional changes
expected for doubled greenhouse gas concentrations. Nevertheless, the
model simulations demonstrate that achieving the highest possible
fidelity when simulating regional climate change requires that climate
models use as input the most accurate (lower) solar irradiance value.
The solar influence on the probability of relatively cold UK winters in the future
Lockwood et al. 2011 Environ. Res. Lett. 6 034004
Recent research has suggested that relatively cold UK winters are more
common when solar activity is low (Lockwood et al 2010 Environ. Res.
Lett. 5 024001). Solar activity during the current sunspot minimum has
fallen to levels unknown since the start of the 20th century (Lockwood
2010 Proc. R. Soc. A 466 303-29) and records of past solar variations
inferred from cosmogenic isotopes (Abreu et al 2008 Geophys. Res. Lett.
35 L20109) and geomagnetic activity data (Lockwood et al 2009 Astrophys.
J. 700 937-44) suggest that the current grand solar maximum is coming
to an end and hence that solar activity can be expected to continue to
decline. Combining cosmogenic isotope data with the long record of
temperatures measured in central England, we estimate how solar change
could influence the probability in the future of further UK winters that
are cold, relative to the hemispheric mean temperature, if all other
factors remain constant. Global warming is taken into account only
through the detrending using mean hemispheric temperatures. We show that
some predictive skill may be obtained by including the solar effect.
Solar cycle modulation of the Pacific-North American teleconnection influence on North American winter climate
Liu et al. 2014 Environ. Res. Lett. 9 024004
We investigate the role of the 11-year solar cycle in modulating the
Pacific-North American (PNA) influence on North American winter climate.
The PNA appears to play an important conduit between solar forcing and
surface climate. The low solar (LS) activity may induce an atmospheric
circulation pattern that resembles the positive phase of the PNA,
resulting in a significant warming over northwestern North America and
significant dry conditions in the Pacific Northwest, Canadian Prairies
and the Ohio-Tennessee-lower Mississippi River Valley. The solar-induced
changes in surface climate share more than 67% and 14% of spatial
variances in the PNA-induced temperature and precipitation changes for
1950-2010 and 1901-2010 periods, respectively. These distinct solar
signatures in North American climate may contribute to deconvolving
modern and past continental-scale climate changes and improve our
ability to interpret paleoclimate records in the region.
Interactions between externally forced climate signals from sunspot peaks and the internally generated Pacific Decadal and North Atlantic Oscillations
van Loon and Meehl 2013 Geophysical Research Letters
When the Pacific Decadal Oscillation is in phase with the 11 year
sunspot cycle, there are positive sea level pressure (SLP) anomalies in
the Gulf of Alaska, nearly no anomalous zonal SLP gradient across the
equatorial Pacific, and a mix of small positive and negative sea surface
temperature (SST) anomalies there. When the two indices are out of
phase, positive SLP anomalies extend farther south in the Gulf of Alaska
and west into eastern Russia, with a strengthened anomalous zonal
equatorial Pacific SLP gradient and larger magnitude and more extensive
negative SST anomalies along the equatorial Pacific. In the North
Atlantic, when the North Atlantic Oscillation (NAO) is in phase with the
sunspot peaks, there is an intensified positive NAO SLP pattern. When
the NAO is out of phase with the peaks, there is the opposite pattern
(negative NAO). The relationships are physically consistent with
previously identified processes and mechanisms and point the way to
further research.
Possible effect of strong solar energetic particle events on polar stratospheric aerosol: a summary of observational results
Mironova and Usoskin 2014 Environmental Research Letters 9, 015002 This letter presents a summary of a phenomenological study of the response of the polar stratosphere to strong solar energetic particle (SEP) events corresponding to ground level enhancements (GLEs) of cosmic rays. This work is focused on evaluation of the possible influence of the atmospheric ionization caused by SEPs upon formation of aerosol particles in the stratosphere over polar regions. Following case studies of two major SEP/GLE events, in January 2005 and September 1989, and their possible effects on polar stratospheric aerosols, we present here the results of an analysis of variations of the daily profiles of the stratospheric aerosol parameters (aerosol extinction for different wavelengths, as well as Angstrom exponent) for both polar hemispheres during SEP/GLE events of July 2000, April 2001 and October 2003, which form already five clear cases corresponding to extreme and strong SEP/GLE events. The obtained results suggest that an enhancement of ionization rate by a factor of about two in the polar region with night/cold/winter conditions can lead to the formation/growing of aerosol particles in the altitude range of 10-25 km. We also present a summary of the investigated effects based on the phenomenological study of the atmospheric application of extreme SEP events.The nature of the solar activity during the Maunder Minimum revealed by the Guliya ice core record
Linglian et al 2000 Chinese Science Bulletin 45, 2118-2125
Whether the solar activity was very low, and especially whether the
solar cycle existed, during the Maunder Minimum (1645-1715 AD), have
been disputed for a long time. In this paper we use the Guliya NO3 data,
which can reflect the solar activity, to analyze the characteristics of
the solar activity during the Maunder Minimum. The results show that
the solar activity was indeed low, and solar cycle displayed normal as
present, i.e. about 11a, in that period. Moreover, it was found that the
solar activity contains a 36-year periodic component probably, which
might be related to the variations in the length of the sunspot cycle.
This finding is of importance for the study of the relationship between
the sun variability and the Earth climate change.
Influence of the Precipitating Energetic Particles on Atmospheric Chemistry and Climate
Rozanov et al. 2012 Surveys in Geophysics 33, 483-501
Abstract We evaluate the influence of the galactic cosmic rays (GCR),
solar proton events (SPE), and energetic electron precipitation (EEP) on
chemical composition of the atmosphere, dynamics, and climate using the
chemistry-climate model SOCOL. We have carried out two 46-year long
runs. The reference run is driven by a widely employed forcing set and,
for the experiment run, we have included additional sources of NOx and
HOx caused by all considered energetic particles. The results show that
the effects of the GCR, SPE, and EEP fluxes on the chemical composition
are most pronounced in the polar mesosphere and upper stratosphere;
however, they are also detectable and statistically significant in the
lower atmosphere consisting of an ozone increase up to 3 % in the
troposphere and ozone depletion up to 8 % in the middle stratosphere.
The thermal effect of the ozone depletion in the stratosphere propagates
down, leading to a warming by up to 1 K averaged over 46 years over
Europe during the winter season. Our results suggest that the energetic
particles are able to affect atmospheric chemical composition, dynamics,
and climate.
Possible effects of atmospheric teleconnections and solar variability on tropospheric and stratospheric temperatures in the Northern Hemisphere
Sfica and Voiculescu 2014 Journal of Atmospheric and Solar-Terrestrial Physics
Possible relationships between tropospheric and stratospheric
temperatures in the Northern Hemisphere and atmospheric oscillations,
solar and geomagnetic activity are described using correlation analysis.
The dependence of correlations on season, solar activity level and
phase of the Quasi Biennial Oscillation (QBO) is also investigated. An
important finding is that the variability of the hemispheric
tropospheric temperature is well connected to the Scandinavian Pattern,
to the Pacific North American teleconnection and less with the North
Atlantic Oscillation. There is also a possible link with the Southern
Oscillation (SO) for winter. Solar UV and cosmic ray flux might
influence tropospheric temperature during warm seasons, solar maximum or
QBO West. Significant correlations between the Northern stratospheric
temperature and the SO is observed especially during the Eastern phase
of QBO and solar minimum. Signatures of geomagnetic variability are seen
in the winter stratospheric temperature. The stratospheric temperature
correlates with the cosmic ray flux and solar UV at annual level at
solar maximum and QBO West. The UV effect at stratospheric level is less
clear than expected. The existence of some correlations between
tropospheric/stratospheric temperatures and internal and external
parameters under certain climatic circumstances and during different
solar cycle phases might help in identifying processes that transfer
energy from the Sun to different atmospheric layers and in assessing
their role in climate variability.
Reduced Solar Activity Disguises Global Temperature Rise
Stauning 2014 Atmospheric and Climate Sciences, 2014, 4, 60-63
The question whether human activities seriously affect climate is asked
with increasing voice these days. Quite understandable since the climate
appears to be out of control with the significant global temperature
increases already seen during the last three decades and with still
heavier temperature increases to come in the future according to
prognoses, among others, in the recent comprehensive IPCC reports [1].
However, the most recent climate data [2], show global temperature
development levelling off or even turning negative since 2001 in
contrast to the anticipated course related to the steady increases in
the concentration in the atmosphere of green-house gasses, primarily
carbon dioxide and methane [1]. The purpose of this communication is to
demonstrate that the reduced rate in the global temperature rise
complies with expectations related to the decaying level of solar
activity according to the relation published in an earlier analysis [3].
Without the reduction in the solar activity-related contributions the
global temperatures would have increased steadily from 1980 to present.
The effects of solar irradiation changes on the migration of the Congo Air Boundary and water levels of paleo-Lake Suguta, Northern Kenya Rift, during the African Humid Period (15-5 ka BP)
Junginger et al. 2014 Palaeogeography, Palaeoclimatology, Palaeoecology
The water-level record from the 300 m deep paleo-lake Suguta (Northern
Kenya Rift) during the African Humid Period (AHP, 15-5 ka BP) helps to
explain decadal to centennial intensity variations in the West African
Monsoon (WAM) and the Indian Summer Monsoon (ISM). This water-level
record was derived from three different sources: (1) grainsize
variations in radiocarbon dated and Rreservoir corrected lacustrine
sediments, (2) the altitudes and ages of paleo-shorelines within the
basin, and (3) the results of hydro-balance modeling, providing S
important insights into the character of water level variations (abrupt
or gradual) in the amplifier paleo-Lake Suguta. The results of this
comprehensive analyses suggest that the AHP N highstand in the Suguta
Valley was the direct consequence of a northeastwards shift in the Congo
Air Boundary (CAB), which was in turn caused by an enhanced atmospheric
pressure gradient between East Africa and India during a northern
hemisphere insolation maximum. Rapidly decreasing water levels of up to
90 m over less than a hundred years are best explained by changes in
solar irradiation either reducing the East African-Indian atmospheric
pressure P gradient and preventing the CAB from reaching the study area,
or reducing the overall humidity in the atmosphere, or a combination of
both these effects. In contrast, although not well documented C in our
record we hypothesize a gradual end of the AHP despite an abrupt change
in the source of precipitation when a decreasing pressure gradient
between Asia and Africa prevented the CAB from reaching the Suguta
Valley. The abruptness was probably buffered by a contemporaneous change
in precession producing an insolation maximum at the equator during
October. Whether or not this is the case, the water-level record from
the Suguta Valley demonstrates the importance of both
orbitally-controlled insolation variations and short-term changes in
solar irradiation as factors affecting the significant water level
variations in East African rift lakes.
Clouds blown by the solar wind
Voiculescu et al. 2013 Environ. Res. Lett. 8, 045032
In this letter we investigate possible relationships between the cloud
cover (CC) and the interplanetary electric field (IEF), which is
modulated by the solar wind speed and the interplanetary magnetic field.
We show that CC at mid-high latitudes systematically correlates with
positive IEF, which has a clear energetic input into the atmosphere, but
not with negative IEF, in general agreement with predictions of the
global electric circuit (GEC)-related mechanism. Thus, our results
suggest that mid-high latitude clouds might be affected by the solar
wind via the GEC. Since IEF responds differently to solar activity than,
for instance, cosmic ray flux or solar irradiance, we also show that
such a study allows distinguishing one solar-driven mechanism of cloud
evolution, via the GEC, from others.
Global warming and solar anomaly
Chakrabarty and Peshin 2013 Indian Journal of Radio & Space Physics
During 2002-2008, there was no increase in global temperature, though
green house gas concentrations had increased. Sun is the ultimate source
of energy. It has been, therefore, examined if there was any anomaly in
the solar characteristics during this period. The sunspot number data
has been used for this purpose. This parameter has an 11-year solar
activity cycle and the same is found in the global temperature. But the
trend in sun's output, after removing solar activity effect, does not
match with the long term trend of global temperature. Peculiarities in
the duration and in the peak value of solar cycle 23 were identified
which might have portended the increase of global temperature during
2002-2008. The possibility of the pause of increase in temperature could
also be that the heat generated due to the increase in the greenhouse
gas concentration was absorbed in deep ocean layer.
papers reported in 2013
Small influence of solar variability on climate over the past millennium
Schurer et al. 2013 Nature Geoscience
The climate of the past millennium was marked by substantial decadal and
centennial scale variability in the Northern Hemisphere. Low solar
activity has been linked to cooling during the Little Ice Age (AD
1450-1850) and there may have been solar forcing of regional warmth
during the Medieval Climate Anomaly (AD 950-1250). The amplitude of the
associated changes is, however, poorly constrained, with estimates of
solar forcing spanning almost an order of magnitude. Numerical
simulations tentatively indicate that a small amplitude best agrees with
available temperature reconstructions. Here we compare the climatic
fingerprints of high and low solar forcing derived from model
simulations with an ensemble of surface air temperature reconstructions
for the past millennium. Our methodology also accounts for internal
climate variability and other external drivers such as volcanic
eruptions, as well as uncertainties in the proxy reconstructions and
model output. We find that neither a high magnitude of solar forcing nor
a strong climate effect of that forcing agree with the temperature
reconstructions. We instead conclude that solar forcing probably had a
minor effect on Northern Hemisphere climate over the past 1,000 years,
while, volcanic eruptions and changes in greenhouse gas concentrations
seem to be the most important influence over this period.
Deep Solar Activity Minima, Sharp Climate Changes, and Their Impact on Ancient Civilizations
Raspopov et al. 2013 Geomagnetism and Aeronomy 53, 917-92
It is shown that, over the past c. 10000 years (the Holocene), deep
Maunder type solar minima have been accompanied by sharp climate
changes. These minima occurred every 2300-2400 years. It has been
established experimentally that, at ca 4.0 ka BP, there occurred a
global change in the structure of atmospheric circulation, which
coincided in time with the discharge of glacial masses from Greenland to
North Atlantic and a solar activity minimum. The climate changes that
took place at ca 4.0 ka BP and the deep solar activity minimum that
occurred at ca 2.5 ka BP affected the development of human society,
leading to the degradation and destruction of a number of ancient
civilizations.
Late Holocene ecohydrological and carbon dynamics of a UK raised bog: impact of human activity and climate change
Turner et al. 2014 Quaternary Science Reviews
Understanding the ecohydrological responses of peatlands to climate
change is particularly challenging over the late Holocene owing to the
confounding influence of anthropogenic activity. To address this, a core
spanning the last c. 2400 years from a raised bog in northern England
was analysed using a comprehensive suite of proxy methods in an attempt
to elucidate the drivers of change. A testate amoebae-based transfer
function was used to quantitatively reconstruct changes in water table
depth, supported by humification analysis and a plant
macrofossil-derived hydroclimatic index. Pollen and plant macrofossil
data were used to examine regional and local vegetation change, and
human impacts were inferred from charcoal and geochemistry.
Chronological control was achieved through a Bayesian age-depth model
based on AMS radiocarbon dates and spheroidal carbonaceous particles,
from which peat and carbon accumulation rates were calculated. Phases of
both increased and decreased bog surface wetness (inferred effective
precipitation) are present, with dry phases at c. AD 320-830, AD
920-1190 and AD 1850-present, and a marked period of increased effective
precipitation at c. AD 1460-1850. Coherence with other records from
across Northern Europe suggests that these episodes are primarily driven
by allogenic climatic change. Periods of high bog surface wetness
correspond to the Wolf, Sporer and Maunder sunspot activity minima,
suggesting solar forcing was a significant driver of climate change over
the last c. 1000 years. Following the intensification of agriculture
and industry over the last two centuries, the combined climatic and
anthropogenic forcing effects become increasingly difficult to separate
due to increases in atmospheric deposition of anthropogenically derived
pollutants, fertilising compounds, and additions of wind-blown soil
dust. We illustrate the need for multiproxy approaches based on
high-resolution palaeoecology and geochemistry to examine the recent
trajectories of peatlands.
The role of the oceans in shaping the tropospheric response to the 11 year solar cycle
Misios and Schmidt 2014 Geophysical Research Letters
Observational data indicate a weakening and poleward shift of the
subtropical tropospheric jets in the maximum phase of the 11 year solar
cycle, commonly explained in terms of a direct "top-down" propagation of
solar signals from the stratosphere to the troposphere. We here
demonstrate possible linkages to oceanic variability, instead. The
observed response of the jets is qualitatively and quantitatively
reproduced in an ensemble of simulations with a global model forced only
at the lower boundary by the observed sea surface temperatures and sea
ice concentrations, while keeping solar cycle forcing constant. The
twentieth century reanalysis, in which only surface observations are
assimilated, is characterized by a similar shift of the jets. These
findings suggest that changes at the ocean surface could contribute
considerably to the poleward shift of the subtropical tropospheric jets,
although a top-down influence on the oceans and hence indirectly on the
jets cannot be excluded.
A lagged response to the 11 year solar cycle in observed winter Atlantic/European weather patterns
Gray et al. 2014 Journal of Geophysical Research: Atmospheres
The surface response to 11 year solar cycle variations is investigated
by analyzing the long-term mean sea level pressure and sea surface
temperature observations for the period 1870-2010. The analysis reveals a
statistically significant 11 year solar signal over Europe, and the
North Atlantic provided that the data are lagged by a few years. The
delayed signal resembles the positive phase of the North Atlantic
Oscillation (NAO) following a solar maximum. The corresponding sea
surface temperature response is consistent with this. A similar analysis
is performed on long-term climate simulations from a coupled
ocean-atmosphere version of the Hadley Centre model that has an extended
upper lid so that influences of solar variability via the stratosphere
are well resolved. The model reproduces the positive NAO signal over the
Atlantic/European sector, but the lag of the surface response is not
well reproduced. Possible mechanisms for the lagged nature of the
observed response are discussed.
Reviewing the effect of CO2 and the sun on global climate
Florides et al. 2013 Renewable and Sustainable Energy Reviews
This paper discusses the effect of the greenhouse phenomenon and CO2 on
global climate and suggests that numerical models that lack adequate
knowledge of fundamental related factors cannot be used to extract
"sound" conclusions. A very basic demonstration of this is done through a
simple comparison between estimates of the forecast for global
temperature increase obtained by various independent studies. Observing
the global temperature and the CO2 atmospheric concentration though the
geological aeons implies no obvious correlation. Physical observation on
other planets like Mars and Venus, needing no numerical modeling,
demonstrates the effect of the atmospheric-CO2 partial pressure on the
temperature of the atmosphere. Moreover the CO2 role as a factor of
danger or a benefactor for life is also addressed. On the other hand the
role of the sun in the presently observed global warming has been
greatly underestimated. Scientific evidence shows that the orbit of the
earth and the Milankovitch cycles greatly affect the climate. A
discussion follows pointing out the prime role that the sun should have
on the earth's climate with regard to solar cycles' activity and
irradiance, cosmic rays and cloud formation. The conclusion drawn here
is that a natural signal of solar forcing has been mistakenly overlooked
for an anthropogenic change, maybe owing to their quite similar effects
on climate. For the moment science does not really have a complete and
total understanding of the factors affecting the earth's complex climate
system and therefore no sound conclusions can be drawn.
Influence of the Pacific Decadal Oscillation, El Nino-Southern Oscillation and solar forcing on climate and primary productivity changes in the northeast Pacific
Patterson et al. 2013 Quaternary International
Evidence of 11-year Schwabe solar sunspot cycles, El Nino-Southern
Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) were
detected in an annual record of diatomaceous laminated sediments from
anoxic Effingham Inlet, Vancouver Island, British Columbia. Radiometric
dating and counting of annual varves dates the sediments from AD
1947-1993. Intact sediment slabs were X-rayed for sediment structure
(lamina thickness and composition based on gray-scale), and subsamples
were examined for diatom abundances and for grain size. Wavelet analysis
reveals the presence of c. 2-3, 4.5, 7 and 9-12 year cycles in the
diatom record and an c. 11-13 year record in the sedimentary varve
thickness record. These cycle lengths suggest that both ENSO and the
sunspot cycle had an influence on primary productivity and sedimentation
patterns. Sediment grain size could not be correlated to the sunspot
cycle although a peak in the grain size data centered around the
mid-1970s may be related to the 1976-1977 Pacific climate shift, which
occurred when the PDO index shifted from negative (cool conditions) to
positive (warm conditions). Additional evidence of the PDO regime shift
is found in wavelet and cross-wavelet results for Skeletonema costatum, a
weakly silicified variant of S. costatum, annual precipitation and
April to June precipitation. Higher spring (April/May) values of the
North Pacific High pressure index during sunspot minima suggest that
during this time, increased cloud cover and concomitant suppression of
the Aleutian Low (AL) pressure system led to strengthened coastal
upwelling and enhanced diatom production earlier in the year. These
results suggest that the 11-year solar cycle, amplified by cloud cover
and upwelling changes, as well as ENSO, exert significant influence on
marine primary productivity in the northeast Pacific. The expression of
these cyclic phenomena in the sedimentary record were in turn modulated
by the phase of PDO, as indicated by the change in period of ENSO and
suppression of the solar signal in the record after the 1976-1977 regime
shift.
Prediction of solar activity for the next 500 years
Steinhilber and Beer 2013 Journal of Geophysical Research
Recently, a new low-noise record of solar activity has been
reconstructed for the past 10 149400 years by combining two Be records
from Greenland and Antarctica with C from tree rings [Steinhilber et
al., 2012]. This record confirms earlier results, namely, that the Sun
has varied with distinct periodicities in the past. We present a
prediction of mean solar magnetic activity averaged over 22 years for
the next 500 years mainly based on the spectral information derived from
the solar activity record of the past. Assuming that the Sun will
continue to vary with the same periodicities for the next centuries, we
extract the spectral information from the past and apply it to two
different methods to predict the future of solar magnetic activity.
First, the two methods are tested by predicting past changes. Our
methods are able to predict periods of high and low solar activities for
a few centuries in the past. However, they are less successful in
predicting the correct amplitude. Then, the methods were used to predict
the period 2000-2500. Both methods predict a period of low activity
around 2100 A.D. Between 2100 and 2350 A.D., the results are
inconsistent regarding the duration of the low-activity state in 2100
A.D. and the level of activity until 2250 A.D. Around 2250 A.D., both
methods predict a period of moderate activity. After 2350 A.D., both
methods point to a period of high activity. The period of high activity
will end around 2400 A.D. and will be followed by a period of moderate
activity.
Lengths of Schwabe cycles in the seventh and eighth centuries indicated by precise measurement of carbon-14 content in tree rings
Miyake et al. 2013 Journal of Geophysical Research
Radiocarbon (14C) is produced in the atmosphere by galactic cosmic rays,
which are modulated by solar magnetic activity. Its content in tree
rings is retained and provides a record of past cosmic ray intensity and
solar activity. We have measured, with 2 year resolution, the 14C
content in Japanese cedar tree rings for the period A.D. 600 to 760,
which includes a small grand solar minimum in the seventh to eighth
centuries. Periodicity analysis of the 14C data shows that there is a
component in the frequency band of the Schwabe cycle, with a period of
12-13 years continuing throughout the minimum. This is the fourth case
in which an increase in the length of the Schwabe cycle has been
observed in a grand solar minimum, after the Maunder Minimum, the
Spoerer Minimum, and the Fourth Century B.C. Minimum.
Global temperatures and sunspot numbers. Are they related?
Gil-Alana et al. 2013 Physica A
This paper deals with the analysis of global temperatures and sunspot
numbers and the relationship between the two. We use techniques based on
the concept of long range dependence. For the temperatures, the best
specification seems to be a fractionally integrated or I(d) model with
an order of integration d of about 0.46 and an estimated time trend
coefficient that suggests that temperatures have increased by about 0.57
C over the last one hundred years. However, for the sunspot numbers, a
cyclical fractional model seems to be more appropriate, with a
periodicity of 11 years per cycle and an order of integration of about
0.40. Thus, the two series display long memory and fractional
integration. However, the fact that both series display poles in the
spectrum at different frequencies implies that we fail to reject the
null hypothesis of no relationship between the two variables in the long
run. Moreover, assuming that the sunspots are exogenous, the results
show no statistical significance of this variable on the global
temperatures, which is one of the main contributions of the present
work.
Does the diurnal temperature range respond to changes in the cosmic ray flux?
Laken and Calogovic 2013 Environmental Research Letters 8, 045018
Recent studies have suggested that measurements of the diurnal
temperature range (DTR) over Europe may provide evidence of a
long-hypothesized link between the cosmic ray (CR) flux and cloud cover.
Such propositions are interesting, as previous investigations of
CR-cloud links are limited by data issues including long-term
reliability and view-angle artifacts in satellite-based cloud
measurements. Consequently, the DTR presents a further independent
opportunity for assessment. Claims have been made that during infrequent
high-magnitude increases (ground level enhancements, GLE) and decreases
(Forbush decreases, Fd) in the CR flux significant anti-correlated DTR
changes may be observed, and the magnitude of the DTR deviations
increases with the size of the CR disturbance. If confirmed this may
have important consequences for the estimation of natural climate
forcing. We analyze these claims, and conclude that no statistically
significant fluctuations in DTR (p < 0.05) are observed. Using
detailed Monte Carlo significance testing we show that past claims to
the contrary result from a methodological error in estimating
significance connected to the effects of sub-sampling.
Terrestrial ground temperature variations in relation to solar magnetic variability, including the present Schwabe cycle
de Jager and Nieuwenhuijzen 2013 Natural Science 5, 1112-1120
We study the influence of solar activity on climate by investigating the
relation between the long-term components of the total magnetic fluxes
of both the equatorial and polar fields of the sun and the average
terrestrial ground temperature. This is done for the period 1610
(beginning of systematic sunspot observations) till present with an
extrapolation to 2015. It is found that from 1610 till about the first
half of the 20th century the variation of the long-term average
terrestrial ground temperatures is chiefly due to the variation of solar
activity, with seemingly random, non-solar residuals. Around 2007,
after the Grand Maximum of the 20th century, solar activity, after
having gone through a remarkable transition period (c. 2005 to c. 2010),
entered into another Grand Episode. That Episode started with the
present solar cycle, in shape comparable to the equally weak Schwabe
cycle #14. The transition period, in combination with the present low
Schwabe cycle causes that the solar contribution to the total
terrestrial temperature variation is small during the on-going decade.
It results in a slowing down of the rise of temperature after c. 2005.
Holocene flood frequency across the Central Alps - solar forcing and evidence for variations in North Atlantic atmospheric circulation
Wirth et al. 2013 Quaternary Science Reviews 80, 112-128
The frequency of large-scale heavy precipitation events in the European
Alps is expected to undergo substantial changes with current climate
change. Hence, knowledge about the past natural variability of floods
caused by heavy precipitation constitutes important input for climate
projections. We present a comprehensive Holocene (10,000 years)
reconstruction of the flood frequency in the Central European Alps
combining 15 lacustrine sediment records. These records provide an
extensive catalog of flood deposits, which were generated by
flood-induced underflows delivering terrestrial material to the lake
floors. The multi-archive approach allows suppressing local weather
patterns, such as thunderstorms, from the obtained climate signal. We
reconstructed mainly late spring to fall events since ice cover and
precipitation in form of snow in winter at high-altitude study sites do
inhibit the generation of flood layers. We found that flood frequency
was higher during cool periods, coinciding with lows in solar activity.
In addition, flood occurrence shows periodicities that are also observed
in reconstructions of 14C and 10B solar activity from C and Be records
(2500-3000, 900-1200, as well as of about 710, 500, 350, 208 (Suess
cycle), 150, 104 and 87 (Gleissberg cycle) years). As atmospheric
mechanism, we propose an expansion/shrinking of the Hadley cell with
increasing/decreasing air temperature, causing dry/wet conditions in
Central Europe during phases of high/low solar activity. Furthermore,
differences between the flood patterns from the Northern Alps and the
Southern Alps indicate changes in North Atlantic circulation. Enhanced
flood occurrence in the South compared to the North suggests a
pronounced southward position of the Westerlies and/or blocking over the
northern North Atlantic, hence resembling a negative NAO state (most
distinct from 4.2 to 2.4 kyr BP and during the Little Ice Age).
South-Alpine flood activity therefore provides a qualitative record of
variations in a paleo-NAO pattern during the Holocene. Additionally,
increased South Alpine flood activity contrasts to low precipitation in
tropical Central America (Cariaco Basin) on the Holocene and centennial
time scale. This observation is consistent with a Holocene southward
migration of the Atlantic circulation system, and hence of the ITCZ,
driven by decreasing summer insolation in the Northern hemisphere, as
well as with shorter-term fluctuations probably driven by solar
activity.
Paleoclimate data-model comparison and the role of climate forcings over the past 1500 years
Phipps et al. 2013 Journal of Climate 26, 6915-6936
The past 1500 years provide a valuable opportunity to study the response
of the climate system to external forcings. However, the integration of
paleoclimate proxies with climate modeling is critical to improving the
understanding of climate dynamics. In this paper, a climate system
model and proxy records are therefore used to study the role of natural
and anthropogenic forcings in driving the global climate. The inverse
and forward approaches to paleoclimate data-model comparison are
applied, and sources of uncertainty are identified and discussed. In the
first of two case studies, the climate model simulations are compared
with multiproxy temperature reconstructions. Robust solar and volcanic
signals are detected in Southern Hemisphere temperatures, with a
possible volcanic signal detected in the Northern Hemisphere. The
anthropogenic signal dominates during the industrial period. It is also
found that seasonal and geographical biases may cause multiproxy
reconstructions to overestimate the magnitude of the long-term
preindustrial cooling trend. In the second case study, the model
simulations are compared with a coral d18O record from the central
Pacific Ocean. It is found that greenhouse gases, solar irradiance, and
volcanic eruptions all influence the mean state of the central Pacific,
but there is no evidence that natural or anthropogenic forcings have any
systematic impact on El Nino-Southern Oscillation. The proxy climate
relationship is found to change over time, challenging the assumption of
stationarity that underlies the interpretation of paleoclimate proxies.
These case studies demonstrate the value of paleoclimate data-model
comparison but also highlight the limitations of current techniques and
demonstrate the need to develop alternative approaches.
Solar forcing of Caribbean drought events during the last millennium
Burn and Palmer 2013 Journal of Quaternary Science
Anthropogenic climate change is expected to increase the frequency of
drought events in the earth's subtropical regions. However, the climate
dynamics of these regions are not fully understood and debate surrounds
how external forcing factors such as solar and volcanic forcing
influence long-term rainfall patterns in the subtropics. Here, we
present the first high-resolution reconstruction of Caribbean drought
events over the last millennium based on analyses of sediment
geochemical data from a continuous high-resolution coastal lake-sediment
record in Jamaica. The record suggests extended episodes of drought
occurred during the so-called Little Ice Age (1400-1850 CE), which were
associated with El-Nino-like conditions in the eastern equatorial
Pacific Ocean and controlled by low natural radiative forcing.
Comparison of the Jamaican drought record with previously published
palaeoclimatic archives from within the circum-Caribbean region suggests
that dry conditions were associated with the southward migration of the
Hadley Cell, a stronger North Atlantic High and the concomitant
intensification of the north-east trade winds and the Caribbean Low
Level Jet. We conclude that pre-industrial climatic change in the region
was probably controlled by solar forcing and modulated by the combined
influence of El Nino Southern Oscillation and the North Atlantic
Oscillation.
North-south palaeohydrological contrasts in the central Mediterranean during the Holocene: tentative synthesis and working hypotheses
Magny et al. 2013 Climate of the Past 9, 2043-2071
On the basis of a multi-proxy approach and a strategy combining
lacustrine and marine records along a north-south transect, data
collected in the central Mediterranean within the framework of a
collaborative project have led to reconstruction of high-resolution and
well-dated palaeohydrological records and to assessment of their spatial
and temporal coherency. Contrasting patterns of palaeohydrological
changes have been evidenced in the central Mediterranean: south (north)
of around 40N of latitude, the middle part of the Holocene was
characterised by lake-level maxima (minima), during an interval dated to
ca. 10 300-4500 cal BP to the south and 9000-4500 cal BP to the north.
Available data suggest that these contrasting palaeohydrological
patterns operated throughout the Holocene, both on millennial and
centennial scales. Regarding precipitation seasonality, maximum humidity
in the central Mediterranean during the middle part of the Holocene was
characterised by humid winters and dry summers north of ca. 40N, and
humid winters and summers south of ca. 40N. This may explain an apparent
conflict between palaeoclimatic records depending on the proxies used
for reconstruction as well as the synchronous expansion of tree species
taxa with contrasting climatic requirements. In addition, south of ca.
40N, the first millennium of the Holocene was characterised by very dry
climatic conditions not only in the eastern, but also in the central-
and the western Mediterranean zones as reflected by low lake levels and
delayed reforestation. These results suggest that, in addition to the
influence of the Nile discharge reinforced by the African monsoon, the
deposition of Sapropel 1 has been favoured (1) by an increase in winter
precipitation in the northern Mediterranean borderlands, and (2) by an
increase in winter and summer precipitation in the southern
Mediterranean area. The climate reversal following the Holocene climate
optimum appears to have been punctuated by two major climate changes
around 7500 and 4500 cal BP. In the central Mediterranean, the Holocene
palaeohydrological changes developed in response to a combination of
orbital, ice-sheet and solar forcing factors. The maximum humidity
interval in the south-central Mediterranean started ca. 10 300 cal BP,
in correlation with the decline (1) of the possible blocking effects of
the North Atlantic anticyclone linked to maximum insolation, and/or (2)
of the influence of the remnant ice sheets and fresh water forcing in
the North Atlantic Ocean. In the north-central Mediterranean, the
lake-level minimum interval began only around 9000 cal BP when the
Fennoscandian ice sheet disappeared and a prevailing positive NAO-(North
Atlantic Oscillation) type circulation developed in the North Atlantic
area. The major palaeohydrological oscillation around 4500-4000 cal BP
may be a non-linear response to the gradual decrease in insolation, with
additional key seasonal and interhemispheric changes. On a centennial
scale, the successive climatic events which punctuated the entire
Holocene in the central Mediterranean coincided with cooling events
associated with deglacial outbursts in the North Atlantic area and
decreases in solar activity during the interval 11 700-7000 cal BP, and
to a possible combination of NAO-type circulation and solar forcing
since ca. 7000 cal BP onwards. Thus, regarding the centennial-scale
climatic oscillations, the Mediterranean Basin appears to have been
strongly linked to the North Atlantic area and affected by solar
activity over the entire Holocene. In addition to model experiments, a
better understanding of forcing factors and past atmospheric circulation
patterns behind the Holocene palaeohydrological changes in the
Mediterranean area will require further investigation to establish
additional high-resolution and well-dated records in selected locations
around the Mediterranean Basin and in adjacent regions. Special
attention should be paid to greater precision in the reconstruction, on
millennial and centennial timescales, of changes in the latitudinal
location of the limit between the northern and southern
palaeohydrological Mediterranean sectors, depending on (1) the intensity
and/or characteristics of climatic periods/oscillations (e.g. Holocene
thermal maximum versus Neoglacial, as well as, for instance, the 8.2 ka
event versus the 4 ka event or the Little Ice Age); and (2) on varying
geographical conditions from the western to the eastern Mediterranean
areas (longitudinal gradients). Finally, on the basis of projects using
strategically located study sites, there is a need to explore possible
influences of other general atmospheric circulation patterns than NAO,
such as the East Atlantic-West Russian or North Sea-Caspian patterns, in
explaining the apparent complexity of palaeoclimatic
(palaeohydrological) Holocene records from the Mediterranean area.
A reconstruction of radiocarbon production and total solar irradiance from the Holocene 14C and CO2 records: implications of data and model uncertainties
Roth and Joos 2013 Climate of the Past 9, 1879-1909
Radiocarbon production, solar activity, total solar irradiance (TSI) and
solar-induced climate change are reconstructed for the Holocene (10 to 0
kyr BP), and TSI is predicted for the next centuries. The
IntCal09/SHCal04 radiocarbon and ice core CO2 records, reconstructions
of the geomagnetic dipole, and instrumental data of solar activity are
applied in the Bern3D-LPJ, a fully featured Earth system model of
intermediate complexity including a 3-D dynamic ocean, ocean sediments,
and a dynamic vegetation model, and in formulations linking radiocarbon
production, the solar modulation potential, and TSI. Uncertainties are
assessed using Monte Carlo simulations and bounding scenarios. Transient
climate simulations span the past 21 thousand years, thereby
considering the time lags and uncertainties associated with the last
glacial termination. Our carbon-cycle-based modern estimate of
radiocarbon production of 1.7 atoms cm-2 s-1 is lower than previously
reported for the cosmogenic nuclide production model by Masarik and Beer
(2009) and is more in line with Kovaltsov et al. (2012). In contrast to
earlier studies, periods of high solar activity were quite common not
only in recent millennia, but throughout the Holocene. Notable
deviations compared to earlier reconstructions are also found on decadal
to centennial timescales. We show that earlier Holocene
reconstructions, not accounting for the interhemispheric gradients in
radiocarbon, are biased low. Solar activity is during 28% of the time
higher than the modern average (650 MeV), but the absolute values remain
weakly constrained due to uncertainties in the normalisation of the
solar modulation to instrumental data. A recently published solar
activity-TSI relationship yields small changes in Holocene TSI of the
order of 1 W m-2 with a Maunder Minimum irradiance reduction of 0.85 +-
0.16 W m-2. Related solar-induced variations in global mean surface air
temperature are simulated to be within 0.1 K. Autoregressive modelling
suggests a declining trend of solar activity in the 21st century towards
average Holocene conditions.
Reconstruction and Prediction of Variations in the Open Solar Magnetic Flux and Interplanetary Conditions
Lockwood 2013 Living Reviews Solar Physics 10, 4
Historic geomagnetic activity observations have been used to reveal
centennial variations in the open solar flux and the near-Earth
heliospheric conditions (the interplanetary magnetic field and the solar
wind speed). The various methods are in very good agreement for the
past 135 years when there were sufficient reliable magnetic
observatories in operation to eliminate problems due to site-specific
errors and calibration drifts. This review underlines the physical
principles that allow these reconstructions to be made, as well as the
details of the various algorithms employed and the results obtained.
Discussion is included of: the importance of the averaging timescale;
the key differences between "range" and "interdiurnal variability"
geomagnetic data; the need to distinguish source field sector structure
from heliospherically-imposed field structure; the importance of
ensuring that regressions used are statistically robust; and uncertainty
analysis. The reconstructions are exceedingly useful as they provide
calibration between the in-situ spacecraft measurements from the past
five decades and the millennial records of heliospheric behaviour
deduced from measured abundances of cosmogenic radionuclides found in
terrestrial reservoirs. Continuity of open solar flux, using sunspot
number to quantify the emergence rate, is the basis of a number of
models that have been very successful in reproducing the variation
derived from geomagnetic activity. These models allow us to extend the
reconstructions back to before the development of the magnetometer and
to cover the Maunder minimum. Allied to the radionuclide data, the
models are revealing much about how the Sun and heliosphere behaved
outside of grand solar maxima and are providing a means of predicting
how solar activity is likely to evolve now that the recent grand maximum
(that had prevailed throughout the space age) has come to an end.
Discussion on climate oscillations: CMIP5 general circulation models versus a semi-empirical harmonic model based on astronomical cycles
Scafetta 2013 Earth Science Reviews
Power spectra of global surface temperature (GST) records (available
since 1850) reveal periodities at about 9.1, 10-11, 19-22 and 59-62
years. Equivalent oscillations are found in numerous multisecular
paleoclimatic records. The CMIP5 general circulation models (GCMs), to
be used in the 2013 IPCC AR5 report, are analyzed and found not able to
reconstruct this variability. In particular, from 2000 to 2013.5 a GST
plateau is observed, while the GCMs predicted a warming of about 2
C/century. In contrast, the hypothesis that the climate is regulated by
specific natural oscillations better interprets the GST records at
multiple time scales. For example, a quasi 60-year natural oscillation
explains the 1850-1880, 1910-1940 and 1970-2000 warming periods, the
1880-1910 and 1940-1970 cooling periods and the post 2000 plateau. This
hypothesis implies that about 50% of the c. 0.5 C global surface warming
observed from 1970 to 2000 was due to natural oscillations of the
climate system, not to anthropogenic forcing as modeled by the GCMs. The
climate sensitivity to CO2 doubling should be reduced from the claimed
2.0-4.5 C range to 1.0-2.3 C with a likely median of c. 1.5 C instead of
c. 3.0 C. Also modern paleoclimatic temperature reconstructions showing
a larger preindustrial variability than the hockey-stick shaped
temperature reconstructions developed in early 2000 imply a lower
anthropogenic effect and a larger solar effect. The observed natural
oscillations could be driven by astronomical forcings. The c. 9.1 year
oscillation appears to be a combination of long soli-lunar tidal
oscillations, while quasi 10-11, 20 and 60 year oscillations are
typically found among major solar and heliospheric oscillations driven
mostly by Jupiter and Saturn movements. Solar models based on
heliospheric oscillations also predict quasi secular (e.g. c. 115 year)
and millennial (e.g. c. 983 year) solar oscillations, which hindcast
observed climate oscillations during the Holocene. It is proposed a
semi-empirical climate model made of six specific astronomical
oscillations as constructors of the natural climate variability spanning
from the decadal to the millennial scales plus a 50% attenuated
radiative warming component deduced from the GCM mean simulation as a
measure of the anthropogenic plus volcano effect. The semi-empirical
model reconstructs the 1850-2012 climatic patterns significantly better
than any CMIP5 GCM simulation. Under the same CMIP5 anthropogenic
emission scenarios, the model projects a possible 2000-2100 average
warming ranging from about 0.3 C to 1.8 C. This range is significantly
below the original CMIP5 GCM ensemble mean projections spanning from
about 1 C to 4 C. Future research should better investigate
space-climate coupling mechanisms and develop more advanced
semi-empirical climate models. HadCRUT3 and HadCRUT4, UAH MSU, RSS MSU,
GISS and NCDC temperature reconstructions are analyzed.
On the insignificance of Herschel's sunspot correlation
Love, 2013 Geophysical Research Letters
We examine William Herschel's hypothesis that solar-cycle variation of
the Sun's irradiance has a modulating effect on the Earth's climate, and
that this is, specifically, manifest as an anticorrelation between
sunspot number and the market price of wheat. Since Herschel first
proposed his hypothesis in 1801, it has been regarded with both interest
and skepticism. Recently, reports have been published that either
support Herschel's hypothesis or rely on its validity. As a test of
Herschel's hypothesis, we seek to reject a null hypothesis of a
statistically random correlation between historical sunspot numbers,
wheat prices in London and the United States, and wheat-farm yields in
the United States. We employ binary-correlation, Pearson-correlation,
and frequency-domain methods. We test our methods using an historical
geomagnetic-activity index, well known to be causally correlated with
sunspot number. As expected, the measured correlation between sunspot
number and geomagnetic activitywould be an unlikely realization of
random data; the correlation is "statistically significant". On the
other hand, measured correlations between sunspot number and wheat-price
and wheat-yield data would be very likely realizations of random data;
these correlations are "insignificant". Therefore, Herschel's hypothesis
must be regarded with skepticism. We compare and contrast our results
with those of other researchers. We discuss procedures for evaluating
hypotheses that are formulated from historical data.
The role of the Sun in atmosphere-ocean coupling
Roy 2013 International Journal of Climatology
An overview of the processes involved in determining the Sun''s
influence on climate is presented in the form of a flow chart. Evidence
and hypotheses concerning the combined influences of the El
Niño-Southern Oscillation, the Quasi-Biennial Oscillation and the Solar
Cycle on the Hadley and Walker circulations are discussed in the context
of atmosphere-ocean coupling, focussing on the Pacific region. It is
shown that the Sun plays a crucial role in ocean-atmosphere coupling but
that this coupling appears to be disturbed during the latter half of
the 20th century, probably related to climate change. The identification
of a solar influence can lead to improved skill in prediction so as to
better inform communities to address/mitigate some of the crucial issues
that are associated with climate change.
Solar and planetary oscillation control on climate change: hind-cast, forecast and a comparison with the CMIP5 GCMs
Scafetta 2013 Energy and Environment 24, 455-496
Global surface temperature records (e.g. HadCRUT4) since 1850 are
characterized by climatic oscillations synchronous with specific solar,
planetary and lunar harmonics superimposed on a background warming
modulation. The latter is related to a long millennial solar oscillation
and to changes in the chemical composition of the atmosphere (e.g.
aerosol and greenhouse gases). However, current general circulation
climate models, e.g. the CMIP5 GCMs, to be used in the AR5 IPCC Report
in 2013, fail to reconstruct the observed climatic oscillations. As an
alternate, an empirical model is proposed that uses: (1) a specific set
of decadal, multidecadal, secular and millennial astronomic harmonics to
simulate the observed climatic oscillations; (2) a 0.45 attenuation of
the GCM ensemble mean simulations to model the anthropogenic and volcano
forcing effects. The proposed empirical model outperforms the GCMs by
better hind-casting the observed 1850-2012 climatic patterns. It is
found that: (1) about 50-60% of the warming observed since 1850 and
since 1970 was induced by natural oscillations likely resulting from
harmonic astronomical forcings that are not yet included in the GCMs;
(2) a 2000-2040 approximately steady projected temperature; (3) a
2000-2100 projected warming ranging between 0.3 C and 1.6 C, which is
significantly lower than the IPCC GCM ensemble mean projected warming of
1.1 oC to 4.1 oC ; (4) an equilibrium climate sensitivity to CO2
doubling centered in 1.35 oC and varying between 0.9 oC and 2.0 oC.
IPCC underestimates the sun's role in climate change
van Geel and Ziegler 2013 Energy and Environment 24, 431-453
For the understanding of current and future climate change it is a basic
pre requisite to properly understand the mechanisms, which controlled
climate change after the Last Ice Age. According to the IPCC 5th
assessment report (in prep.) the Sun has not been a major driver of
climate change during the post-Little Ice Age slow warming, and
particularly not during the last 40 years. This statement requires
critical review as the IPCC neglects strong paleo-climatologic evidence
for the high sensitivity of the climate system to changes in solar
activity. This high climate sensitivity is not alone due to variations
in total solar irradiance-related direct solar forcing, but also due to
additional, so-called indirect solar forcings. These include
solar-related chemical-based UV irradiance-related variations in
stratospheric temperatures and galactic cosmic ray-related changes in
cloud cover and surface temperatures, as well as ocean oscillations,
such as the Pacific Decadal Oscillation and the North Atlantic
Oscillation that significant affect the climate. As it is still
difficult to quantify the relative contribution of combined direct and
indirect solar forcing and of increased atmospheric CO2 concentrations
to the slow warming of the last 40 years, predictions about future
global warming based exclusively on anthropogenic CO2 emission scenarios
are premature. Nevertheless, the cyclical temperature increase of the
20th century coincided with the buildup and culmination of the Grand
Solar Maximum that commenced in 1924 and ended in 2008. The anticipated
phase of declining solar activity of the coming decades will be a
welcome "natural laboratory" to clarify and quantify the present and
future role of solar variation in climate change.
Impact of a potential 21st century "grand solar minimum" on surface temperatures and stratospheric ozone
Anet et al. 2013 Geophysical Research Letters
We investigate the effects of a recently proposed 21st century
Dalton-minimum-like decline of solar activity on the evolution of
Earths' climate and ozone layer. Three sets of 2-member ensemble
simulations, radiatively forced by a mid-level emission scenario (IPCC
RCP4.5), are performed with the atmosphere-ocean chemistry climate model
AOCCM SOCOL3-MPIOM, one with constant solar activity, the other two
with reduced solar activity and different strength of the solar
irradiance forcing. A future grand solar minimum will reduce the global
mean surface warming of 2K between 1986-2005 and 2081-2100 by 0.2 to 0.3
K. Furthermore, the decrease in solar UV radiation leads to a
significant delay of stratospheric ozone recovery by 10 years and
longer. Therefore, the effects of a solar activity minimum, should it
occur, may interfere with international efforts for the protection of
global climate and the ozone layer.
A Holocene paleoclimate reconstruction for eastern Canada based on d18O cellulose of Sphagnum mosses from Mer Bleue Bog
El Bilali et al. 2013 The Holocene
We present a c. 9200 yr high-resolution oxygen isotope record of plant
cellulose (d18Ocel) from the peat deposits of Mer Bleue Bog, Ontario and
apply it as a proxy for paleotemperature reconstruction in Eastern
Canada. The results show that d18Ocel of Sphagnum follows the general
pattern of the Northern Hemisphere reconstructed paleotemperature record
for the last 2000 years at a ratio of c. 0.2%d18Ocel/°C. The d18Ocel
record of ombrotrophic phase of Mer Bleue Bog is also in accordance with
major features of the Holocene sunspot number reconstruction. Three
distinct time intervals have low d18Ocel values: 200-800 cal. BP
("Little Ice Age"); 2800-3400 cal. BP synchronous to a cooling period
reported elsewhere in North America; and 4200-4600 cal. BP corresponding
to a cooling interval in the North Atlantic region. These cooling
periods also correlate well with negative excursions in the Holocene
sunspot and cosmogenic 10Be records. A fourth period of low d18Ocel
values between AD 1810 and 1820 may be related to the extremely cold
summer of 1816 and cooler subsequent years, which occurred in the
aftermath of the Tambora volcanic eruption, or possibly cooling
associated with the early 19th century Dalton solar minimum. The results
also indicate the presence of millennial-scale cycles possibly
comparable with the globally recognized Bond cycles that have been
correlated to fluctuations in solar irradiance.
A modern Maunder Minimum would not stave off global warming
Schultz 2013 EOS 94, 276
Roughly every 11 years, the Sun's activity swings, a peak-to-peak
oscillation in the presence of sunspots on the solar surface. From
around 1645 to 1715, however, researchers think that this largely
reliable trend in solar activity stalled. Now known as the Maunder
Minimum, the period saw not just a prolonged dearth of sunspot activity
but also a likely reduction in the output of energy from the Sun.
Researchers estimate that the Maunder Minimum could have caused a
reduction in solar irradiance of around 0.01% to 0.25%, a shift that
contributed to a drop of globally averaged surface air temperature of a
few tenths of a degree.
Climate change and decadal to centennial-scale climate periodicities recorded in a late Holocene NE Pacific marine record: Examining the role of solar forcing
Galloway et al. 2013 Palaeogeography, Palaeoclimatology, Palaeoecology
We present a decadal-scale late Holocene climate record based on
diatoms, biogenic silica, and grain size from a 12-m sediment core
(VEC02A04) obtained from Frederick Sound in the Seymour-Belize Inlet
Complex of British Columbia, Canada. Sediments are characterized by
graded, massive, and laminated intervals. Laminated intervals are most
common between c. 2948-2708 cal. yr BP and c. 1992-1727 cal. yr BP.
Increased preservation of laminated sediments and diatom assemblage
changes at this time suggest that climate became moderately drier and
cooler relative to the preceding and succeeding intervals. Spectral and
wavelet analyses are used to test for statistically significant
periodicities in time series of proxies of primary production (total
diatom abundance, biogenic silica) and hydrology (grain size) preserved
in the Frederick Sound record. Periodicities of c. 42-53, 60-70, 82-89,
241-243, and 380 yrs are present. Results are compared to reconstructed
sunspot number data of Solanki et al. (2004) using cross wavelet
transform to evaluate the role of solar forcing on NE Pacific climate.
Significant common power of periodicities between c. 42-60, 70-89,
204-243, and of 380 yrs occur, suggesting that celestial forcing
impacted late Holocene climate at Frederick Sound. Replication of the c.
204-243 yr periodicity in sunspot time series is most pronounced
between c. 2900 cal. yr BP and c. 2000 cal. yr BP, broadly correlative
to the timing of maximum preservation of laminated sedimentary
successions and diatom assemblage changes. High solar activity at the
Suess/de Vries band may have been manifested as a prolonged westward
shift and/or weakening of the Aleutian Low in the mid-late Holocene,
which would have diverted fewer North Pacific storms and resulted in the
relatively dry conditions reconstructed for the Seymour-Belize Inlet
Complex.
The Effects of Solar Variability on Earth's Climate: A Workshop Report (September 8-9, 2011)
NAS 2012 The National Academies Press, Washington, 71 pp.
On September 8-9, 2011, experts in solar physics, climate models,
paleoclimatology, and atmospheric science assembled at the National
Center for Atmospheric Research (NCAR) in Boulder, Colorado for a
workshop to consider the Sun's variability over time and potential
Sun-climate connections. While it does not provide findings,
recommendations, or consensus on the current state of the science, The
Effects of Solar Variability on Earth's Climate: A Workshop Report
briefly introduces the primary topics discussed by presenters at the
event. As context for these topics, the summary includes background
information on the potential Sun-climate connection, the measurement
record from space, and potential perturbations of climate due to
long-term solar variability. This workshop report also summarizes some
of the science questions explored by the participants as potential
future research endeavors.
Reconciliation of modeled climate responses to spectral solar forcing
Wen et al. 2013 Journal of Geophysical Research
The SIM (Spectral Irradiance Monitor) on SORCE (Solar Radiation and
Climate Experiment) provides more spectrally complete daily SSI
(spectral solar irradiance) measurements than ever before, allowing us
to explore chemical and physical processes in the Earth's ocean and
atmosphere system. However, the newly observed SSI instigated
controversies in the Sun-climate community on whether the SIM-observed
trends are true solar variations and on whether climate responses are in
phase or out of phase with solar forcing. In this study, we focus on
resolving two apparently contradictory results published on possible
temperature responses to SIM-derived solar forcing. When applying
extreme scenarios of SIM-based spectral solar forcing in a
radiative-convective model (RCM), we find that some apparently
contradictory results can be explained by the different methods used to
apply the SIM SSI data. It is clear that accurate SSI data are essential
for accurate climate simulations and that climate modelers need to take
care how they apply these data.
Atmospheric annular modes in simulation over the past millennium: No long-term response to external forcing
Gómez-Navarro and Zorita 2013 Geophysical Research Letters 40, 1-5
This study analyzes whether the imprint of external forcings can be
detected in the long-term evolution of the main atmospheric circulation
patterns in climate simulations over the last millennium. The external
forcing is not found to significantly add variability in any frequency
band compared to control simulations where the external drivers are kept
constant. Additionally, a method designed to detect a common signal in
the time evolution of these circulation patterns among all simulations
is proposed, and employed to demonstrate that the null hypothesis of an
evolution dominated by internal variability cannot be rejected
regardless of the time smoothing applied to the series. Given that the
fingerprint of external forcings on atmospheric circulation has been
successfully detected in simulations of the 20th century climate and in
future climate change projections, we argue that either the effect of
past natural forcing is too small, state-of-the-art climate models
underestimate their climate sensitivity, or the anthropogenic forcing
qualitatively differs from the natural forcing in its effect on main
circulation patterns.
Cosmic-ray-driven reaction and greenhouse effect of halogenated molecules: culprits for atmospheric ozone depletion and global climate change
Lu, 2012. International Journal of Modern Physics B 27, 1350073
This study is focused on the effects of cosmic rays (solar activity) and
halogen-containing molecules (mainly chlorofluorocarbons - CFCs) on
atmospheric ozone depletion and global climate change. Brief reviews are
first given on the cosmic-ray-driven electron-induced-reaction (CRE)
theory for O3 depletion and the warming theory of halogenated molecules
for climate change. Then natural and anthropogenic contributions to
these phenomena are examined in detail and separated well through
in-depth statistical analyses of comprehensive measured datasets of
quantities, including cosmic rays (CRs), total solar irradiance, sunspot
number, halogenated gases (CFCs, CCl4 and HCFCs), CO2, total O3, lower
stratospheric temperatures and global surface temperatures. For O3
depletion, it is shown that an analytical equation derived from the CRE
theory reproduces well 11-year cyclic variations of both polar O3 loss
and stratospheric cooling, and new statistical analyses of the CRE
equation with observed data of total O3 and stratospheric temperature
give high linear correlation coefficients >= 0.92. After the removal
of the CR effect, a pronounced recovery by 20~25% of the Antarctic O3
hole is found, while no recovery of O3 loss in mid-latitudes has been
observed. These results show both the correctness and dominance of the
CRE mechanism and the success of the Montreal Protocol. For global
climate change, in-depth analyses of the observed data clearly show that
the solar effect and human-made halogenated gases played the dominant
role in Earth's climate change prior to and after 1970, respectively.
Remarkably, a statistical analysis gives a nearly zero correlation
coefficient (R = -0.05) between corrected global surface temperature
data by removing the solar effect and CO2 concentration during
1850-1970. In striking contrast, a nearly perfect linear correlation
with coefficients as high as 0.96-0.97 is found between corrected or
uncorrected global surface temperature and total amount of stratospheric
halogenated gases during 1970-2012. Furthermore, a new theoretical
calculation on the greenhouse effect of halogenated gases shows that
they (mainly CFCs) could alone result in the global surface temperature
rise of ~0.6°C in 1970-2002. These results provide solid evidence that
recent global warming was indeed caused by the greenhouse effect of
anthropogenic halogenated gases. Thus, a slow reversal of global
temperature to the 1950 value is predicted for coming 5~7 decades. It is
also expected that the global sea level will continue to rise in coming
1~2 decades until the effect of the global temperature recovery
dominates over that of the polar O3 hole recovery; after that, both will
drop concurrently. All the observed, analytical and theoretical results
presented lead to a convincing conclusion that both the CRE mechanism
and the CFC-warming mechanism not only provide new fundamental
understandings of the O3 hole and global climate change but have
superior predictive capabilities, compared with the conventional models.
Multidecadal to multicentury scale collapses of Northern Hemisphere monsoons over the past millennium
Asmerom et al. 2013 PNAS
Late Holocene climate in western North America was punctuated by periods
of extended aridity called megadroughts. These droughts have been
linked to cool eastern tropical Pacific sea surface temperatures (SSTs).
Here, we show both short-term and long-term climate variability over
the last 1,500 y from annual band thickness and stable isotope
speleothem data. Several megadroughts are evident, including a
multicentury one, AD 1350-1650, herein referred to as Super Drought,
which corresponds to the coldest period of the Little Ice Age.
Synchronicity between southwestern North American, Chinese, and West
African monsoon precipitation suggests the megadroughts were hemispheric
in scale. Northern Hemisphere monsoon strength over the last millennium
is positively correlated with Northern Hemisphere temperature and North
Atlantic SST. The megadroughts are associated with cooler than average
SST and Northern Hemisphere temperatures. Furthermore, the megadroughts,
including the Super Drought, coincide with solar insolation minima,
suggesting that solar forcing of sea surface and atmospheric
temperatures may generate variations in the strength of Northern
Hemisphere monsoons. Our findings seem to suggest stronger (wetter)
Northern Hemisphere monsoons with increased warming.
Solar influence on climate variability and human development during the Neolithic: evidence from a high-resolution multi-proxy record from Templevanny Lough, County Sligo, Ireland
Stolze et al. 2013 Quaternary Science Reviews 67, 138-159
The relationship between climatic variations, vegetation dynamics and
early human activity between c. 4150-2860 BC was reconstructed from a
high-resolution pollen and geochemical record obtained from a small lake
located in County Sligo, Ireland. The proxy record suggests the
existence of a woodland with a largely closed canopy at the start of the
fourth millennium BC. Only minor human disturbance is recorded.
Following an episode of increased rainfall at c. 3990 BC, a decrease in
the elm population occurred between c. 3970 and 3820 BC. This coincided
with a period of warming and drying climatic conditions and an initial
increase in anthropogenic activities. A second episode of high
precipitation between c. 3830-3800 BC was followed by a steep increase
in human impact on the landscape, which became most pronounced between
c. 3740 and 3630 BC. At this time, the lake level of Templevanny Lough
was at its lowest during the Neolithic. The onset of wetter and cooler
conditions after c. 3670 BC, representing the transition from the Early
to the Middle Neolithic, coincided with a period of woodland recovery.
The Middle Neolithic was characterised by pronounced climatic
oscillations including periods of substantial rainfall between c. 3600
and 3500 BC and between c. 3500 and 3460 BC. A nearly century-long
climatic amelioration between c. 3460-3370 BC facilitated a revival of
human activity on a small scale around the lake. Abandonment of the area
and full woodland recovery occurred after a period of particularly wet
and cool conditions ranging from c. 3360-3290 BC. The pollen and
geochemistry data suggest that the Late Neolithic was marked by a period
of ameliorated conditions between c. 3110-3050 BC that was followed by
two episodes of high rainfall at c. 3060-3030 BC and c. 2940-2900 BC.
The timing of the climatic shifts inferred from the Templevanny Lough
record is in agreement with those of moisture/precipitation and
temperature reconstructions from northern and western Europe and the
Alps, suggesting that the studied period was characterised by a
high-frequency climate variability. The results of the present study
imply that human development during the Irish Neolithic was influenced
by climatic variations. These climatic shifts correspond to variations
in solar activity, suggesting a solar forcing on climate.
Claim of solar influence is on thin ice: are 11-year cycle solar minima associated with severe winters in Europe?
van Oldenborgh et al. 2013 Environmental Research Letters 8, 024014
A recent paper in Geophysical Research Letters, 'Solar influence on
winter severity in central Europe', by Sirocko et al (2012 Geophys. Res.
Lett. 39 L16704) claims that 'weak solar activity is empirically
related to extremely cold winter conditions in Europe' based on analyses
of documentary evidence of freezing of the River Rhine in Germany and
of the Reanalysis of the Twentieth Century (20C). However, our attempt
to reproduce these findings failed. The documentary data appear to be
selected subjectively and agree neither with instrumental observations
nor with two other reconstructions based on documentary data. None of
these datasets show significant connection between solar activity and
winter severity in Europe beyond a common trend. The analysis of Sirocko
et al of the 20C circulation and temperature is inconsistent with their
time series analysis. A physically-motivated consistent methodology
again fails to support the reported conclusions. We conclude that
multiple lines of evidence contradict the findings of Sirocko et al.
The importance of time-varying forcing for QBO modulation of the atmospheric 11-year solar cycle signal
Matthes et al. 2013 Journal Of Geophysical Research Atmospheres
We present results from three multi-decadal sensitivity experiments with
time-varying solar cycle and Quasi-Biennial Oscillation (QBO) forcings
using NCAR's Whole Atmosphere Community Climate Model (WACCM3.1). The
model experiments are unique compared to earlier studies as they use
time-varying forcings either for the solar cycle only and the QBO, both
individually and combined. The results show that the annual mean solar
response in the tropical upper stratosphere is independent of the
presence of the QBO. The response in the middle to lower stratosphere
differs depending on the presence of the QBO and the solar cycle but is
statistically indistinguishable in the three experiments. The seasonal
evolution of the solar and the combined solar-QBO signals reveals a
reasonable agreement with observations only for the experiment in which
both the solar cycle and the QBO forcing are present, suggesting that
both forcings are important to generate the observed response. More
stratospheric warmings occur during solar maximum and QBO west
conditions. This appears to be the result of a QBO modulation of the
background zonalmean wind climatology, which modifies the solar signal.
Depending on the background wind the small initial early winter solar
signal in the subtropical upper stratosphere/lower mesosphere is
enhanced during QBO east and diminished during QBO west conditions. This
consequently influences the transfer of the solar-QBO signal during
winter and results in the observed differences during late winter.
Could a future "Grand Solar Minimum" like the Maunder Minimum stop global warming?
Meehl et al. 2013 Geophysical Research Letters
A future Maunder Minimum type grand solar minimum, with total solar
irradiance reduced by 0.25% over a 50 year period from 2020 to 2070, is
imposed in a future climate change scenario experiment (RCP4.5) using,
for the first time, a global coupled climate model that includes ozone
chemistry and resolved stratospheric dynamics (Whole Atmosphere
Community Climate Model). This model has been shown to simulate two
amplifying mechanisms that produce regional signals of decadal climate
variability comparable to observations, and thus is considered a
credible tool to simulate the Sun's effects on Earth's climate. After
the initial decrease of solar radiation in 2020, globally averaged
surface air temperature cools relative to the reference simulation by up
to several tenths of a degree Centigrade. By the end of the grand solar
minimum in 2070, the warming nearly catches up to the reference
simulation. Thus, a future grand solar minimum could slow down but not
stop global warming.
Solar influenced late Holocene temperature changes on the northern Tibetan Plateau
YuXin et al. 2013 Chinese Science Bulletin 58, 1053-1059
Considerable efforts have been made to extend temperature records beyond
the instrumental period through proxy reconstructions, in order to
further understand the mechanisms of past climate variability. Yet, the
global coverage of existing temperature records is still limited,
especially for some key regions like the Tibetan Plateau and for earlier
times including the Medieval Warm Period (MWP). Here we present
decadally-resolved, alkenone-based, temperature records from two lakes
on the northern Tibetan Plateau. Characterized by marked temperature
variability, our records provide evidence that temperatures during the
MWP were slightly higher than the modern period in this region. Further,
our temperature reconstructions, within age uncertainty, can be well
correlated with solar irradiance changes, suggesting a possible link
between solar forcing and natural climate variability, at least on the
northern Tibetan Plateau.
The AD775 cosmic event revisited: the Sun is to blame
Usoskin et al. 2013 Astronomy & Astrophysics 552, L3
Aims. Miyake et al. (2012, Nature, 486, 240, henceforth M12) recently
reported, based on 14C data, an extreme cosmic event in about AD775.
Using a simple model, M12 claimed that the event was too strong to be
caused by a solar flare within the standard theory. This implied a new
paradigm of either an impossibly strong solar flare or a very strong
cosmic ray event of unknown origin that occurred around AD775. However,
as we show, the strength of the event was significantly overestimated by
M12. Several subsequent works have attempted to find a possible exotic
source for such an event, including a giant cometary impact upon the Sun
or a gamma-ray burst, but they are all based on incorrect estimates by
M12. We revisit this event with analysis of new datasets and consistent
theoretical modelling. Methods. We verified the experimental result for
the AD775 cosmic ray event using independent datasets including 10Be
series and newly measured 14C annual data. We surveyed available
historical chronicles for astronomical observations for the period
around the AD770s to identify potential sightings of aurorae borealis
and supernovae. We interpreted the 14C measurements using an appropriate
carbon cycle model. Results. We show that: (1) The reality of the AD775
event is confirmed by new measurements of 14C in German oak; (2) by
using an inappropriate carbon cycle model, M12 strongly overestimated
the event''s strength; (3) the revised magnitude of the event (the
global 14C production Q = (1.1 - 1.5) x 108 atoms/cm2) is consistent
with different independent datasets (14C, 10Be, 36Cl) and can be
associated with a strong, but not inexplicably strong, solar energetic
particle event (or a sequence of events), and provides the first
definite evidence for an event of this magnitude (the fluence >30 MeV
was about 4.5 x 1010 cm-2) in multiple datasets; (4) this
interpretation is in agreement with increased auroral activity
identified in historical chronicles. Conclusions. The results point to
the likely solar origin of the event, which is now identified as the
greatest solar event on a multi-millennial time scale, placing a strong
observational constraint on the theory of explosive energy releases on
the Sun and cool stars.
Terrestrial effects of possible astrophysical sources of an AD 774-775 increase in 14C production
Thomas et al. 2013 Geophysical Research Letters
We examine possible sources of a substantial increase in tree ring 14C
measurements for the years AD 774-775. Contrary to claims regarding a
coronal mass ejection (CME), the required CME energy is not several
orders of magnitude greater than known solar events. We consider solar
proton events (SPEs) with three different fluences and two different
spectra. The data may be explained by an event with fluence about one
order of magnitude beyond the October 1989 SPE. Two hard spectrum cases
considered here result in moderate ozone depletion, so no mass
extinction is implied, though we do predict increases in erythema and
damage to plants from enhanced solar UV. We are able to rule out an
event with a very soft spectrum that causes severe ozone depletion and
subsequent biological impacts. Nitrate enhancements are consistent with
their apparent absence in ice core data. The modern technological
implications of such an event may be extreme, and considering recent
confirmation of superflares on solar-type stars, this issue merits
attention.
Modeled rapid adjustments in diurnal temperature range response to CO2 and solar forcings
Jackson and Foster 2013 Journal Of Geophysical Research: Atmospheres
We used the National Center for Atmospheric Research single column
climate model to determine if rapid adjustments to surface heat fluxes
contribute to a change in skin surface or surface air diurnal
temperature range (DTR) under 2 × CO2 and -2% solar forcings. An
ensemble of model runs was employed with locations selected to represent
a range of different climatic conditions and with forcing implemented
hourly throughout the diurnal cycle. The change in skin surface DTR and
surface energy fluxes during the 3 days after forcing were used to
quantify the rapid adjustment response and temperature related feedback.
Averaged over all locations, skin surface DTR reduced by 0.01C after
CO2 forcing and included a rapid adjustment to skin surface DTR of
-0.12C. Skin surface DTR reduced by 0.17C after solar forcing and
included a rapid adjustment of -0.01C. The rapid adjustments in skin
surface DTR were associated with rapid adjustments in surface sensible
and latent heat fluxes necessary to balance the energy budget
immediately after forcing. We find that the sensitivity of skin surface
DTR to mean temperature related feedback is the same for CO2 and solar
forcings when skin surface DTR rapid adjustments are allowed for. Rapid
adjustments played a key role in the geographic variation of the skin
surface DTR response to forcing. Our results suggest that diurnal
variations in trends of downwelling longwave radiation and rapid
reductions in DTR associated with CO2 forcing potentially contributed to
the observed global trend in surface air DTR.
On the origin of multidecadal to centennial Greenland temperature anomalies over the past 800 yr
Kobashi et al. 2013 Climate of the Past 9, 583-596
The surface temperature of the Greenland ice sheet is among the most
important climate variables for assessing how climate change may impact
human societies due to its association with sea level rise. However, the
causes of multidecadal-to-centennial temperature changes in Greenland
temperatures are not well understood, largely owing to short
observational records. To examine these, we calculated the Greenland
temperature anomalies (GTA[G-NH]) over the past 800 yr by subtracting
the standardized northern hemispheric (NH) temperature from the
standardized Greenland temperature. This decomposes the Greenland
temperature variation into background climate (NH); polar amplification;
and regional variability (GTA[G-NH]). The central Greenland polar
amplification factor as expressed by the variance ratio Greenland/NH is
2.6 over the past 161 yr, and 3.3-4.2 over the past 800 yr. The
GTA[G-NH] explains 31-35 % of the variation of Greenland temperature in
the multidecadal-to-centennial time scale over the past 800 yr. We found
that the GTA[G-NH] has been influenced by solar-induced changes in
atmospheric circulation patterns such as those produced by the North
Atlantic Oscillation/Arctic Oscillation (NAO/AO). Climate modeling and
proxy temperature records indicate that the anomaly is also likely
linked to solar-paced changes in the Atlantic meridional overturning
circulation (AMOC) and associated changes in northward oceanic heat
transport.
Solar influence on climate variability and human development during the Neolithic: evidence from a high-resolution multi-proxy record from Templevanny Lough, County Sligo, Ireland
Stolze et al. 2013 Quaternary Science Reviews 67, 138-159
The relationship between climatic variations, vegetation dynamics and
early human activity between c. 4150-2860 BC was reconstructed from a
high-resolution pollen and geochemical record obtained from a small lake
located in County Sligo, Ireland. The proxy record suggests the
existence of a woodland with a largely closed canopy at the start of the
fourth millennium BC. Only minor human disturbance is recorded.
Following an episode of increased rainfall at c. 3990 BC, a decrease in
the elm population occurred between c. 3970 and 3820 BC. This coincided
with a period of warming and drying climatic conditions and an initial
increase in anthropogenic activities. A second episode of high
precipitation between c. 3830-3800 BC was followed by a steep increase
in human impact on the landscape, which became most pronounced between
c. 3740 and 3630 BC. At this time, the lake level of Templevanny Lough
was at its lowest during the Neolithic. The onset of wetter and cooler
conditions after c. 3670 BC, representing the transition from the Early
to the Middle Neolithic, coincided with a period of woodland recovery.
The Middle Neolithic was characterised by pronounced climatic
oscillations including periods of substantial rainfall between c. 3600
and 3500 BC and between c. 3500 and 3460 BC. A nearly century-long
climatic amelioration between c. 3460-3370 BC facilitated a revival of
human activity on a small scale around the lake. Abandonment of the area
and full woodland recovery occurred after a period of particularly wet
and cool conditions ranging from c. 3360-3290 BC. The pollen and
geochemistry data suggest that the Late Neolithic was marked by a period
of ameliorated conditions between c. 3110-3050 BC that was followed by
two episodes of high rainfall at c. 3060-3030 BC and c. 2940-2900 BC.
The timing of the climatic shifts inferred from the Templevanny Lough
record is in agreement with those of moisture/precipitation and
temperature reconstructions from northern and western Europe and the
Alps, suggesting that the studied period was characterised by a
high-frequency climate variability. The results of the present study
imply that human development during the Irish Neolithic was influenced
by climatic variations. These climatic shifts correspond to variations
in solar activity, suggesting a solar forcing on climate.
Geomagnetic field variations in Western Europe from 1500BC to 200 AD. Part II: new intensity secular variation curve
Hervé et al. in press Physics of the Earth and Planetary Interiors
In order to extend the secular variation curve (SVC) of archaeointensity
in Western Europe to the first millennium BC, we studied 24 kilns and
hearths in place, 2 displaced hearths and 6 sets of pottery sherds from
French archaeological sites. Archaeological artefacts, radiocarbon and
dendrochronology dated the acquisition of the thermoremanent
magnetization (TRM) carried by the studied objects. Rock magnetism
experiments suggest that the main carrier of the magnetization is a
Ti-poor titanomagnetite. Archaeointensity was determined by the
Thellier-Thellier classical protocol with pTRM-checks. A strict criteria
set was applied to select only the most reliable results with linear
NRM-TRM diagrams (55% of total specimens). This study demonstrates that
pottery sherds with two TRMs give reliable archaeointensities in the
low-temperature interval, if the NRM-TRM diagram is adequately adjusted.
Eighteen new mean archaeointensities (14 corrected from the anisotropy
of TRM and 16 from cooling rate) were computed. The comparison with
previously published Western Europe paleointensities show a strong
dispersion between data primarily due to their variable quality. Western
Europe data were weighted following the archaeointensity protocol, the
number of specimens per site and the type of studied materials, in order
to better highlight the secular variation of archaeointensity during
the first millennium BC. The SVC, built with sliding windows of 160
years shifted every 50 years, presents (at Paris) a maximum of 90uT
around 800BC and a minimum of 60uT around 250BC. These archaeointensity
maximum and minimum correspond to cusps of the geomagnetic field
direction in Western Europe. This new curve is consistent with
Mesopotamian and Eastern Europe data. The archaeointensity secular
variation in Western Europe predicted by global geomagnetic models
CALS3k.4, ARCH3k.1 and ARCH3k_cst.1 is smoother than our SVC. We used
our directional dataset (Hervé et al., 2012a) to build a new Western
Europe VGPs and VDMs mean curves. Comparison with the predictions given
by the global models points out a possible persistent non-dipole fields
effect over Europe between 1000BC and 600-500BC. Finally, we note that
the strong variations of intensity of the geomagnetic field (with a mean
decrease rate per century close to 6uT) will be useful for
archaeomagnetic dating purposes.
A synthesis of the Antarctic surface mass balance during the last 800 yr
Frezotti et al. 2013 The Cryosphere 7, 303-319
Global climate models suggest that Antarctic snowfall should increase in
a warming climate and mitigate rises in the sea level. Several
processes affect surface mass balance (SMB), introducing large
uncertainties in past, present and future ice sheet mass balance. To
provide an extended perspective on the past SMB of Antarctica, we used
67 firn/ice core records to reconstruct the temporal variability in the
SMB over the past 800 yr and, in greater detail, over the last 200 yr.
Our SMB reconstructions indicate that the SMB changes over most of
Antarctica are statistically negligible and that the current SMB is not
exceptionally high compared to the last 800 yr. High-accumulation
periods have occurred in the past, specifically during the 1370s and
1610s. However, a clear increase in accumulation of more than 10 % has
occurred in high SMB coastal regions and over the highest part of the
East Antarctic ice divide since the 1960s. To explain the differences in
behaviour between the coastal/ice divide sites and the rest of
Antarctica, we suggest that a higher frequency of blocking anticyclones
increases the precipitation at coastal sites, leading to the advection
of moist air in the highest areas, whereas blowing snow and/or erosion
have significant negative impacts on the SMB at windy sites. Eight
hundred years of stacked records of the SMB mimic the total solar
irradiance during the 13th and 18th centuries. The link between those
two variables is probably indirect and linked to a teleconnection in
atmospheric circulation that forces complex feedback between the
tropical Pacific and Antarctica via the generation and propagation of a
large-scale atmospheric wave train.
Variation of the Schwabe Cycle length during the Grand Solar Minimum in the 4th Century BC deduced from radiocarbon content in tree rings
Nagaya et al. 2012 Solar Physics 280, 223-236
Solar activity alternates between active and quiet phases with an
average period of 11 years, and this is known as the Schwabe cycle.
Additionally, solar activity occasionally falls into a prolonged quiet
phase (grand solar minimum), as represented by the Maunder Minimum in
the 17th century, when sunspots were almost absent for 70 years and the
length of the Schwabe cycle increased to 14 years. To examine the
consistency of the cycle length characteristics during the grand solar
minima, the carbon-14 contents in single-year tree rings were measured
using an accelerator mass spectrometer as an index of the solar
variability during the grand solar minimum of the 4th century BC. The
signal of the Schwabe cycle was detected with a statistical confidence
level of higher than 95% by wavelet analysis. This is the oldest
evidence for the Schwabe cycle at the present time, and the cycle length
is considered to have increased to approximately 16 years during the
grand solar minimum of the 4th century BC. This result confirms the
association between the increase of the Schwabe cycle length and the
weakening of solar activity, and indicates the possible prolonged
absence of sunspots in the 4th century BC as during the Maunder Minimum.
Theoretical implications from solar dynamo theory are discussed in
order to identify the trigger of prolonged sunspot absence. A possible
association between the long-term solar variation around the 4th century
BC and terrestrial cooling in this period is also discussed.
Phytolith records of the climate change since the past 15000 years in the middle reach of the Yangtze River in China
Gu et al. 2012 Frontiers of Earth Science 6, 10-17
Based on 14C dating and core sediments survey, phytolith records are
employed to reconstruct paleovegetation and paleoclimate in the Jianghan
Plain in the middle reach of the Yangtze River. Phytoliths identified
are assigned into 21 well-described morphotypes and divided into four
groups (Poaceae, fern, coniferous and broad-leaved). The phytolith
assemblages together with warmth index (Iw) are divided into 18
ecological zones, which reflect a complete vegetation history related to
climate change in the middle reach of the Yangtze River during the past
15000 years. On the basis of the correlation of phytolith records with
the paleoclimatic indicators from stalagmite, peatland, North Atlantic
deep-sea sediments, Loess Plateau of Central China, and Arabic Sea
sediments, eight climatic phases are identified included Last Glacial
Maximum (LGM) (20 - 14.8 cal kaBP), Last Deglaciation (LDG) (14.8 - 11.9
cal kaBP), low-temperature phase in the Early Holocene (11.9 - 8 cal
kaBP), Holocene Optimum (8 - 4.9 cal kaBP), Holocene Katathermal (4.9 -
1.1 cal kaBP), Medieval Warmth Period (MWP) (1.1 - 0.7 cal kaBP), Little
Ice Age (LIA) (0.7 - 0.15 cal kaBP), and Modern Warming (0.15 cal kaBP -
present). Climatic events such as Bolling-Allerod warm intervals, Older
Dryas, Inter-Allerod Cold Period, and Younger Dryas, and eight Holocene
Bond events (B1-8) have been identified since the LDG. Our results
demonstrate that the evolution of the climate in the research area has a
strong link with the Indian Summer Monsoon (SW Monsoon), Asian Summer
Monsoon (SE Monsoon), and Holocene events in North Atlantic
simultaneously, which might indicate that solar variability affects the
Earth surface climate system at the centennial and millennial scales.
A possible solar pacemaker for Holocene fluctuations of a salt-marsh in southern Italy
Di Rita 2013 Quaternary International 288, 239-248
This study is aimed at verifying the possible influence of solar
activity on the coastal vegetation development in the Tavoliere Plain
(south Adriatic region, Italy) between 6350 and 4000 cal BP, when
regular fluctuations of halophilic vegetation are recorded by pollen. A
wavelet analysis, applied to the percentage values of glasswort
vegetation is consistent with periodicities of solar activity and other
palaeoenvironmental and palaeoclimate proxies in the literature. A
comparison of salt-marsh pollen indicators (Salicornia type and Ruppia
maritima) with the 10Be dataset from the Greenland ice core GISP2, on
the basis of their independent chronologies, reveals a strong visual
correlation, indicating that the minima of salt-marsh percentages match
minima in the 10Be curve, corresponding to solar activity maxima,
associated with warm and arid phases at the middle latitudes. The
Tavoliere salt-marsh appears to have contracted during the arid/warm
phases associated to maxima of solar activity and to have expanded
during the wet/cold phases of solar minima. This coastal area,
characterized by a very flat topography and arid climate, appears to
have been very sensitive to even minor hydrological and climate changes.
Changes of solar activity, determining extensive environmental
transformations, were also possibly responsible for the abandonment of
the human coastal settlements of one of the most important Neolithic
archaeological districts of Italy.
Influence of the Pacific Decadal Oscillation, El Nino-Southern Oscillation and solar forcing on climate and primary productivity changes in the northeast Pacific
Patterson et al. in press Quaternary International
Evidence of 11-year Schwabe solar sunspot cycles, El Niño-Southern
Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) were
detected in an annual record of diatomaceous laminated sediments from
anoxic Effingham Inlet, Vancouver Island, British Columbia. Radiometric
dating and counting of annual varves dates the sediments from AD
1947-1993. Intact sediment slabs were X-rayed for sediment structure
(lamina thickness and composition based on gray scale), and subsamples
were examined for diatom abundances and for grain size. Wavelet analysis
reveals the presence of c. 2-3, c. 4.5, c. 7 and c. 9-12-year cycles in
the diatom record and an c. 11-13 year record in the sedimentary varve
thickness record. These cycle lengths suggest that both ENSO and the
sunspot cycle had an influence on primary productivity and sedimentation
patterns. Sediment grain size could not be correlated to the sunspot
cycle although a peak in the grain size data centered around the
mid-1970s may be related to the 1976-1977 Pacific climate shift, which
occurred when the PDO index shifted from negative (cool conditions) to
positive (warm conditions). Additional evidence of the PDO regime shift
is found in wavelet and cross wavelet results for Skeletonema costatum, a
weakly silicified variant of S. costatum, annual precipitation and
April to June precipitation. Higher spring (April/May) values of the
North Pacific High pressure index during sunspot minima suggest that
during this time, increased cloud cover and concomitant suppression of
the Aleutian Low (AL) pressure system led to strengthened coastal
upwelling and enhanced diatom production earlier in the year. These
results suggest that the 11-year solar cycle, amplified by cloud cover
and upwelling changes, as well as ENSO, exert significant influence on
marine primary productivity in the northeast Pacific. The expression of
these cyclic phenomena in the sedimentary record were in turn modulated
by the phase of PDO, as indicated by the change in period of ENSO and
suppression of the solar signal in the record after the 1976-1977 regime
shift.
A study on possible solar and geomagnetic effects on the precipitation over Northwestern Argentina
Heredia and Elias 2013 Advances in Space Research
The precipitation over Tucuman (26.8 S; 65.2 W), which is representative
of the Northwestern region of Argentina, is analyzed in search of an
association with solar and geomagnetic activity, with the purpose of
contributing to the controversial issue on the connection between
climate variation and anthropogenic vs. natural forcing. Monthly time
series of precipitation, sunspot number (Rz), and aa index were used for
the period 1884-2010. A wavelet analysis was performed first which, due
to the time series length, shows significant results only for
periodicities lower than 32 years. Due to the transient character and
non-constant phase of the results, any sustained wavelet coherence
between precipitation and either sunspots or aa could be noticed. Moving
averages and correlations were also assessed. The 11 and 22-year
running mean of precipitation is positively correlated to Rz and aa when
the whole period of analysis is considered. However, a shift in the
long-term behavior of precipitation is noticed around 1940, which
implies different correlation values with Rz and aa when the period
before or after this year are considered. The solar cycle length is also
considered for this statistical study and partly confirms the results
obtained with Rz and aa. We propose plausible physical explanations
based on geomagnetic activity and total solar irradiance effects over
atmospheric circulation that could support the statistical result. A
deeper analysis and broader geographical coverage is needed in order to
detect a connection between precipitation and solar variability
discernible from greenhouse gases effects. We emphasize the idea of the
importance of recognizing and quantifying the different forcing acting
on precipitation (or any other climate parameter), which sometimes can
be barely evident from a solely statistical analysis.
The planetary hypothesis revived
Charbonneau 2013 Nature 493, 613-614
The Sun's magnetic activity varies cyclically over a period of about 11
years. An analysis of a new, temporally extended proxy record of this
activity hints at a possible planetary influence on the amplitude of the
cycle.
Using data to attribute episodes of warming and cooling in instrumental records
Tung and Zhou 2013 PNAS
The observed global-warming rate has been nonuniform, and the cause of
each episode of slowing in the expected warming rate is the subject of
intense debate. To explain this, nonrecurrent events have commonly been
invoked for each episode separately. After reviewing evidence in both
the latest global data (HadCRUT4) and the longest instrumental record,
Central England Temperature, a revised picture is emerging that gives a
consistent attribution for each multidecadal episode of warming and
cooling in recent history, and suggests that the anthropogenic global
warming trends might have been overestimated by a factor of two in the
second half of the 20th century. A recurrent multidecadal oscillation is
found to extend to the preindustrial era in the 353-y Central England
Temperature and is likely an internal variability related to the
Atlantic Multidecadal Oscillation (AMO), possibly caused by the
thermohaline circulation variability. The perspective of a long record
helps in quantifying the contribution from internal variability,
especially one with a period so long that it is often confused with
secular trends in shorter records. Solar contribution is found to be
minimal for the second half of the 20th century and less than 10% for
the first half. The underlying net anthropogenic warming rate in the
industrial era is found to have been steady since 1910 at 0.07-0.08
C/decade, with superimposed AMO-related ups and downs that included the
early 20th century warming, the cooling of the 1960s and 1970s, the
accelerated warming of the 1980s and 1990s, and the recent slowing of
the warming rates. Quantitatively, the recurrent multidecadal internal
variability, often underestimated in attribution studies, accounts for
40% of the observed recent 50-y warming trend.
High-resolution analysis of upper Miocene lake deposits: Evidence for the influence of Gleissberg-band solar forcing
Kern et al. 2013 Palaeogeography, Palaeoclimatology, Palaeoecology 370, 167-183
A high-resolution multi-proxy analysis was conducted on a 1.5-m-long
core of Tortonian age (~ 10.5 Ma; Late Miocene) from Austria (Europe).
The lake sediments were studied with a 1-cm resolution to detect all
small-scale variations based on palynomorphs (pollen and dinoflagellate
cysts), ostracod abundance, geochemistry (carbon and sulfur) and
geophysics (magnetic susceptibility and natural gamma radiation). Based
on an already established age model for a longer interval of the same
core, this sequence can be limited to approx. two millennia of Late
Miocene time with a resolution of ~ 13.7 years per sample. The previous
study documented the presence of solar forcing, which was verified
within various proxies on this 1.5-m core by a combination of REDFIT
spectra and Gaussian filters. Significant repetitive signals ranged in
two discrete intervals corresponding roughly to 55-82 and 110-123 years,
fitting well within the lower and upper Gleissberg cycle ranges. Based
on these results, the environmental changes along the 2000-year Late
Miocene sequence are discussed. No major ecological turnovers are
expected in this very short interval. Nonetheless, even within this
brief time span, dinoflagellates document rapid changes between
oligotrophic and eutrophic conditions, which are frequently coupled with
lake stratification and dysoxic bottom waters. These phases prevented
ostracods and molluscs from settling and promoted the activity of sulfur
bacteria. The pollen record indicates rather stable wetland vegetation
with a forested hinterland. Shifts in the pollen spectra can be mainly
attributed to variations in transport mechanisms. These are represented
by a few phases of fluvial input but mainly by changes in wind intensity
and probably also wind direction. Such influence is most likely caused
by solar cycles, leading to a change in source area for the input into
the lake. Furthermore, these solar-induced variations seem to be
modulated by longer solar cycles. The filtered data display comparable
patterns and modulations, which seem to be forced by the 1000-year and
1500-year cycles. The 1000-year cycle modulated especially the lake
surface proxies, whereas the 1500-year cycle is mainly reflected in
hinterland proxies, indicating strong influence on transport mechanisms.
Paleoclimate of the Southern Adriatic Sea region during the 'Medieval Climate Anomaly' reflected by organic walled dinoflagellate cysts
Chen et al. 2013 The Holocene
To obtain insight into the character and forcing of southern Italian
climate change during the 'Medieval Climate Anomaly' (c. AD 900-1200),
marine sediments deposited between AD 990 and 1200 from the Gulf of
Taranto have been analyzed for their dinoflagellate cyst content with a
3.5 yr resolution. The reconstructed sea surface temperature (SST)
appears to be lower than today. We observe a clear 11.4 yr cyclicity in
the reconstructed SST series. Furthermore, there is a good matching
between SST and global 14C anomalies. This suggests that solar activity
might have had an important influence on the local climate during
Medieval time. Short-term fluctuations in accumulation rates of aerobic
degradation resistant species that react sensitively on the trophic
state of the upper waters and/or are characteristic for river plume
waters indicate that the trophic state of the upper waters is closely
linked to river discharge, which in turn is strongly related to
precipitation in Italy. We reconstruct low river
discharge/precipitations in the Adriatic area synchronous to widespread
drought events in other nearby subtropical regions. We attribute this to
NAO and ENSO related large-scale ocean-atmosphere circulation shifts
during the Medieval period. Furthermore, we suggest that eruptions of
southern Italian volcanoes might have influenced the local upper water
nutrient conditions as well.
Influence of solar activity on breaching, overflowing and course-shifting events of the Lower Yellow River in the late Holocene
Wang & Su 2013 The Holocene
The Lower Yellow River (LYR) has been characterized as a frequently
breaching, overflowing and shifting river in historical periods.
Understanding the factors that influence the LYR variations is critical
for river management and disaster prevention. This study constructed a
spatio-temporal data base of the LYR's breaching and overflowing events
(BOEs) and course-shifting events (CSEs) occurring in the late Holocene.
The data base and corresponding solar activity data were analyzed to
determine the overall influence, temporal influence and spatial
influence of solar activity on the LYR. Results showed that 75.5% of the
LYR CSEs and 61.7% of the LYR BOEs occurred in sunspot number decline
phases of 11 yr solar cycles, suggesting that the LYR changed more
frequently during the sunspot number decline phases. The underlying
mechanism of this phenomenon was further interpreted as the high
correlation between sunspot decline phases and heavy rainfall in the
middle reaches of Yellow River (MYR). Five of the six heavy rainfall
years over the last 60 years and 14 of the 16 well-known heavy rainfall
records from 132 BC to AD 1933 in the MYR occurred in sunspot decline
phases. Heavy rainfall in the MYR promoted the increase of the LYR
runoff and the sediment rate and then raised the possibility of the
occurrence of BOEs and CSEs. The study also found that the frequency of
BOEs was positively related to the fluctuation amplitude of the sunspot
maximum intensity in long time series. The flow directions of the LYR
courses were found to affect the influence of solar activity on BOEs.
The highest correlation between sunspot decline phases and BOEs was
presented during the lifetime of eastward flows while the lowest during
the lifetime of northward flows. In addition, human activities may
undermine the impact of solar activities on the LYR changes.
Are the sunspots really vanishing? Anomalies in solar cycle 23 and implications for long-term models and proxies
Clete and Lefevre 2012 J. Space Weather Space Clim. 2 A06
Context: The elapsed solar cycle (23) ended with an exceptionally long
period of low activity and with unprecedented low levels for various
series of solar irradiance and particle flux measurements. This
unpredicted evolution of solar activity raised multiple questions about a
future decline of the solar cycles and launched a quest for precursor
signs of this possible deep solar transition over the last decade. Aim:
We present here a review and overall interpretation of most current
diagnostics of solar cycle 23, including the recent disagreements that
appeared among solar reference indices and standard solar-based
geo-indices, the indication of a changed pattern of internal torsional
waves (helioseismology) or the announced fading and magnetic weakening
of sunspots. Methods: Based on a statistical analysis of detailed
sunspot properties over the last 24 years, we complete the picture with
new evidence of a strong global deficit of the smallest sunspots
starting around 2000, in order to answer the question: are all sunspots
about to disappear? Results: This global scale-dependent change in
sunspot properties is confirmed to be real and not due to uncontrolled
biases in some of the indices. It can also explain the recent
discrepancies between solar indices by their different sensitivities to
small and weak magnetic elements (small spots). The International
Sunspot Index Ri, based on unweighted sunspot counts, proved to be
particularly sensitive to this particular small-scale solar evolution.
Conclusions: Our results and interpretation show the necessity to look
backwards in time, more than 80 years ago. Indeed, the Sun seems to be
actually returning to a past and hardly explored activity regime ending
before the 1955-1995 Grand Maximum, which probably biased our current
space-age view of solar activity.
Influence of orbital forcing and solar activity on water isotopes in precipitation during the mid- and late Holocene
Dietrich et al. 2013 Climate of the Past 9, 13-26
In this study we investigate the impact of mid- and late Holocene
orbital forcing and solar activity on variations of the oxygen isotopic
composition in precipitation. The investigation is motivated by a
recently published speleothem d18O record from the well-monitored Bunker
Cave in Germany. The record reveals some high variability on
multi-centennial to millennial scales that does not linearly correspond
to orbital forcing. Our model study is based on a set of novel climate
simulations performed with the atmosphere general circulation model
ECHAM5-wiso enhanced by explicit water isotope diagnostics. From the
performed model experiments, we derive the following major results: (1)
the response of both orbital and solar forcing lead to changes in
surface temperatures and d18O in precipitation with similar magnitudes
during the mid- and late Holocene. (2) Past d18O anomalies correspond to
changing temperatures in the orbital driven simulations. This does not
hold true if an additional solar forcing is added. (3) Two orbital
driven mid-Holocene experiments, simulating the mean climate state
approximately 5000 and 6000 yr ago, yield very similar results. However,
if an identical additional solar activity-induced forcing is added, the
simulated changes of surface temperatures as well as d18O between both
periods differ. We conclude from our simulation results that non-linear
effects and feedbacks of the orbital and solar activity forcing
substantially alter the d18O in precipitation pattern and its relation
to temperature change.
Summed radiocarbon probability density functions cannot prove solar forcing of Central European lake-level changes
Bleicher, 2013 The Holocene
It has been argued that Central European lake levels were driven by
solar activity. This interpretation rests on the comparison of a score
record of radiocarbon dates with the 14C residual curve. This score
record is a variant of a cumulative probability density function (CPF).
In this paper it is argued that this method is not valid because the
shape of the CPF is determined by the calibration curve. This hypothesis
is tested by a set of null models. An alternative interpretation is
given according to which only few episodes of Holocene lake-level
changes were climatically driven, while most of the time non-climatic
factors were dominating. On a more general level some methodological
issues of CPFs are discussed and exemplified by the comparison of
dendrochronological results from archaeological settlements and a CPF
created using radiocarbon dates from the same settlements.
A Mechanism for Lagged North Atlantic Climate Response to Solar Variability
Scaife et al. 2013 Geophysical Research Letters, in press
Variability in solar irradiance has been connected to changes in surface
climate in the North Atlantic through both observational and climate
modelling studies which suggest a response in the atmospheric
circulation that resembles the North Atlantic Oscillation or its
hemispheric equivalent the Arctic Oscillation. It has also been noted
that this response appears to follow the changes in solar irradiance by a
few years, depending on the exact indicator of solar variability. Here
we propose and test a mechanism for this lag based on the known impact
of atmospheric circulation on the Atlantic Ocean, the extended memory of
ocean heat content anomalies and their subsequent feedback onto the
atmosphere. We use results from climate model experiments to develop a
simple model for the relationship between solar variability and North
Atlantic climate.
Circulation changes in the winter lower atmosphere and long-lasting solar/geomagnetic activity
Bochnicek et al. 2012 Ann. Geophys. 30, 1719-1726
The paper describes the association between high long-lasting
solar/geomagnetic activity and geopotential height (GPH) changes in the
winter lower atmosphere, based on their development in the Northern
Hemisphere in the winter periods (December-March) of 1950-1969 and
1970-2002. Solar/geomagnetic activity is characterised by the 60-day
mean of the sunspot number R/by the 60-day mean of the daily sum of the
Kp index. The GPH distributions in the lower atmosphere are described by
60-day anomalies from their long-term daily average at 20 hPa/850 hPa.
The data have been adopted from the NCEP/NCAR reanalysis. The 60-day
mean values of solar/geomagnetic activity and GPH anomalies were
calculated in five-day steps over the whole winter period. The analysis
was carried out using composite maps which represent their distribution
of the GPH anomalies during high solar activity (R > 100) and high
geomagnetic activity ( Kp > 20). Analysis has shown that the dis-
tribution of GPH anomalies depends on solar activity, geo-magnetic
activity and the phase of winter period (early or late winter). The
nature of this relationship then depends on the time interval involved,
i.e. 1950-1969 or 1970-2002. Positive anomalies in the polar
stratosphere (20 hPa) were detected during the whole winter periods of
the years 1950-1969. Significant anomalies were detected in the lower
tropo- sphere (850 hPa) during the second half of the winter period. The
distribution of GPH anomalies on the maps compiled with regard to solar
activity was similar to the distribution on maps compiled with regard
to geomagnetic activity. In the interval 1970-2002, significant negative
GPH anomalies were detected in the stratosphere at high latitudes, and
positive anomalies were detected in the region of low latitudes. The
distribution of GPH anomalies in the lower troposphere was substantially
affected by situations in which, together with high solar activity,
also high geomagnetic activity occurred.
Orbital and solar forcing of shifts in Mid- to Late Holocene flood intensity from varved sediments of pre-alpine Lake Ammersee (southern Germany)
Czymzik et al. 2013 Quaternary Science Reviews 61, 96-110
Microfacies analyses and X-ray fluorescence scanning (u-XRF) at sub-mm
resolution were conducted on the varved Mid- to Late Holocene interval
of two sediment profiles from pre-alpine Lake Ammersee (southern
Germany). The coring sites are located in a proximal (AS10prox) and
distal (AS10dist) position towards the main tributary River Ammer, in
1.8 km distance from each other. To shed light on sediment distribution
within the lake, particular emphasis was (1) the detection of
intercalated detrital layers and their micro-sedimentological features,
and (2) intra-basin correlation of these event deposits. Detrital layers
were dated by microscopic varve counting, verified by accelerator mass
spectrometry 14C dating of terrestrial plant macrofossils. Since c. 5500
varve years (vyr) BP, in total 1573 detrital layers were detected in
either one or both of the investigated sediment profiles. Based on their
microfacies, geochemistry, and proximal-distal deposition pattern,
detrital layers were interpreted as River Ammer flood deposits. Earlier
studies on flood layer seasonality have proven that flood layer
deposition occurs predominantly during spring and summer, the flood
season at Lake Ammersee. Most prominent features of the record are the
onset of regular flood layer deposition at c. 5500 vyr BP in AS10prox
and c. 2800 vyr BP in AS10dist as well as three major increases in mean
flood layer thickness at c. 5500, 2800, and 400 vyr BP. Integrating
information from both sediment profiles allowed to interpret these
changes in terms of shifts towards higher mean flood intensity. Proposed
triggering mechanisms are gradual reduction in Northern Hemisphere
orbital summer forcing and superimposed centennial-scale solar activity
minima. Likely responses to this forcing are enhanced equator-to-pole
temperature gradients and changes in synoptic-scale atmospheric
circulation. The consequences for the Ammersee region are more intense
cyclones leading to extremer rainfall and flood events in spring and
summer.
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.
Links to this post
Create a Link