Water Vapor, NOT CO2 is the Most Effective Greenhouse Gas
In terms of mass, water vapour is much more prevalent (about 0.3% of atmospheric
mass, compared to about 0.06% for CO2), and so is ~80% of all greenhouse gases by
mass (~90% by volume). However, the radiative importance is less (since all molecules
are not created equal).
. . . it's clear that water vapour is the single most important absorber (between
36% and 66% of the greenhouse effect), and together with clouds makes up between
66% and 85%. CO2 alone makes up between 9 and 26%,
. . . the maximum supportable number for the importance of water vapour alone is
about 60-70% and for water plus clouds 80-90% of the present day greenhouse effect.
(Of course, using the same approach, the maximum supportable number for CO2 is 20-30%,
and since that adds up to more than 100%, there is a slight problem with such estimates!).</i>
Water vapour is the most important greenhouse gas in the atmosphere.” (IPCC AR4,
p 632). Local
The IPCC reports have minimized the effects of UHI on climate for quite some time.
From Warwick Hughes:
The IPCC drew that conclusion from the Jones et al 1990 Letter to Nature which
examined temperature data from regions in Eastern Australia, Western USSR and Eastern
China, to conclude that “In none of the three regions studied is there any indication
of significant urban influence..” That has led to the IPCC claim that for decades,
urban warming is less than 0.05 per century.
In it, Jones identifies an urban warming signal in China of 0.1 degrees C per decade.
Or, if you prefer, 1 degree C per century. Not negligible by any means. Here is
Global surface temperature trends, based on land and marine data, show warming
of about 0.8°C over the last 100 years. This rate of warming is sometimes questioned
because of the existence of well-known Urban Heat Islands (UHIs). We show examples
of the UHIs at London and Vienna, where city center sites are warmer than surrounding
rural locations. Both of these UHIs however do not contribute to warming trends over
the 20th century because the influences of the cities on surface temperatures have
not changed over this time. In the main part of the paper, for China, we compare
a new homogenized station data set with gridded temperature products and attempt
to assess possible urban influences using sea surface temperature (SST) data sets
for the area east of the Chinese mainland. We show that all the land-based data sets
for China agree exceptionally well and that their residual warming compared to the
SST series since 1951 is relatively small compared to the large-scale warming. Urban-related
warming over China is shown to be about 0.1°C decade−1 over the period 1951–2004,
with true climatic warming accounting for 0.81°C over this period.
Even though Jones tries to minimize the UHI effect elsewhere, saying the UHI trends
don’t contribute to warming in London and Vienna, what is notable about the paper
is that Jones has been minimizing the UHI issues for years and now does an about
face on China. And even more notable is that Jones result are directly at odds with
another researcher at Hadley, Dr. David Parker.
It seems that Parker is looking more and more foolish with his attempts to make UHI
“disappear” To back that up, the National Weather Service includes the UHI factor
in one of it’s training course ( NOAA Professional Competency Unit 6 ) using Reno,
In the PUC6 they were also kind enough to provide a photo essay of their own as well
as a graph. You can click the aerial photo to get a Google Earth interactive view
of the area. The ASOS USHCN station is right between the runways.
This is NOAA’s graph showing the changes to the official climate record when they
made station moves:
Source for 24a and 24b: NOAA Internal Training manual, 2004-2007
What is striking about this is that here we have NOAA documenting the effects of
an “urban heat bubble” something that Parker 2003 et al say “doesn’t exist“, plus
we have inclusion a site with known issues, held up as a bad example for training
the operational folks, being used in a case study for the new USHCN2 system.
So if NOAA trains for UHI placement, and Hadley’s Dr. Jones admits it is real and
quantifies it, I’m comfortable in saying that Parker’s claims of UHI being negligible
are pure rubbish.
Its all about location, location, location. And climate monitoring stations that
are poorly sited and that have been overrun by urban growth clearly don’t give a
pure signal for assessment of long term climate trends. This puts a real kink in
the validity of the surface temperature data in GISS and HadCRUT and could go a long
way towards explaining the divergence between satellite and surface temperatures
in recent years.