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 esterday
saw the release of yet another cookie-cutter global-warming report
claiming that the world is warming and that man is to blame. This
one is from the prestigious National Academy of Sciences, but what
we find within is unimpressive and disappointing.
Indeed, it is 23 pages of linguistic trickery that when parsed
says little. It is likely to alarm those who don't understand scientific
methodology or the nuances of the global warming-debate, i.e., most
of the public. Judging by the way it has been reported in the press,
this is clearly an area of concern.
The report states, "Despite the uncertainties, there is general
agreement that the observed warming is real and particularly strong
within the past 20 years. Whether it is consistent with the change
that would be expected in response to human activities is dependent
upon what assumptions one makes about the time history of
atmospheric concentrations of the various forcing agents, particularly
aerosols" (emphasis added).
It also says, "The predicted warming of 3 degrees C (5.4 degrees
F) by the end of the 21st century is consistent with the assumptions
about how clouds and atmospheric relative humidity will react to
global warming" (emphasis added).
Of course the predictions are consistent with the assumptions.
But the assumptions are the issue here. If the assumptions are correct,
then the global-warming advocates have a case; if not, they don't.
That is where the scientific debate rages today and pretending that
it isn't is useless and uninformative.
Assumptions need to be tested by empirical evidence, however, and
many of the most important ones haven't been. The report correctly
points out that the primary assumption driving speculations about
global warming is the water vapor feedback effect. According to
this assumption, a small temperature increase caused by rising atmospheric
concentrations of manmade greenhouse gases would lead to increased
evaporation. Higher water vapor levels — a major greenhouse gas
— in the atmosphere, would raise global temperatures even further.
Indeed, the lion's share of the predicted warming depends on this
assumption.
Absent climate feedbacks, says the report, Earth's temperature
would increase 1.2 degrees C (2.2 degrees F) at most. Until recently
the positive feedback assumption had not been tested. In March,
however, the Bulletin of the American Meteorological Society
published an empirical study that found the assumption to be wrong.
What it found was a negative feedback powerful enough to offset
all other positive feedback effects. Other important assumptions
have also gone by the wayside in the face of actual evidence. (For
a broader analysis of key global-warming assumptions see
http://www.cei.org/OnPointReader.asp?ID=1477.)
The report also discussed whether the Summary for Policymakers
of the Third Assessment Report of the United Nations' Intergovernmental
Panel on Climate Change (IPCC) accurately reflects the findings
of the underlying report. It concluded that the summary "reflects
less emphasis on communicating the basis for uncertainty and a stronger
emphasis on areas of major concern associated with human-induced
climate change," but that "most changes that did occur
lacked significant impact," implying that changes of significant
impact did occur.
Chapter 7 of the IPCC report on physical processes, for instance,
is 35 pages long. It discusses extensively the problems with the
ability to model the atmospheric processes that govern climate change.
One of the major problems it discusses is the inability to accurately
reflect cloud dynamics, which is directly relevant to the water
vapor issue.
This lengthy chapter was summarized in one sentence in the Summary
for Policymakers. It states, "Understanding of climate processes
and their incorporation in climate models have improved, including
water vapor, sea-ice dynamics, and ocean-heat transport." This
might be defensible as a stand-alone statement, but it hardly summarizes
the chapter.
To be fair to the members of the committee who wrote the report,
it does heavily qualify its claims. If you read the report carefully,
it becomes evident that there are serious problems with the global-warming
hypothesis. It points out, for example, that the inability of the
climate models to simulate natural variability makes it very difficult
to establish a causal link between rising concentrations of greenhouse
gases and rising global temperatures. In other words, if you don't
understand the climate's natural variations, you can't determine
whether the observed changes are natural or man-made.
Fortunately, the White House understands the gist of the report
and the importance of the caveats. "This report shows what
is known and certain, and that which is unknown or surmised,"
said White House press secretary Ari Fleischer. "For instance,
it concludes that the Earth is warming. But it is inconclusive on
why — whether it's man-made causes or whether it's natural causes."
There is no smoking gun here. The best available evidence still
suggests that the amount of warming likely to occur over the next
100 years will be trivial.
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