TCS Daily

What Exactly Are the Global Warming Models Saying?

By Anthony Lupo - September 20, 2004 12:00 AM

It's fright month for adherents of global warming who, following upon Russia's failure to meet the Sept. 6 deadline for signing a global treaty to curb greenhouse gas emissions, apparently want to scare the public at large to pressure the Bush administration to support such measures.

Taking aim at a key electoral state -- Florida -- a former British Cabinet minister, Stephen Byers, opined that the United States was already experiencing the effects of global warming with the spate of hurricanes that have inundated or threatened that state's coasts.

And the Union of Concerned Scientists issued a study last week about catastrophic regional effects of global warming on the state with the most population and electoral votes -- California. The Union tried to give its work the aura of respectability by basing it on study published by the National Academy of Sciences on climate effects in California based upon an examination of results from various global climate models. Indeed, most of the reporting about catastrophic consequences of climate change are said to have been produced by the latest and most advanced computer modeling technique, so called Climate Circulation Models, or GCMs.

Those computer models claim to show global temperatures increasing anywhere from 1.4 C - 5.8 C (2.4 F to 10.4 F) by the year 2100 alone[1]. Some scientists playing the game "what if" then regionalize the results and claim the warming will have catastrophic impacts -- from drought and excessive heat waves in California that destroy its wine crops through violent weather events such as hurricanes in Florida. The truth of the matter is otherwise, however, and one must listen to what the scientists themselves say in order to know the actual facts.

Most scientific assessments[1] show that the climate scenarios generated by various GCMs cluster into the low end of the range for the global temperature rises given above. Moreover, if the observed trends are extrapolated outward, they fit into the GCM cluster in the low end of the spectrum as well[1]. And nearly all GCM simulations, as well as observational evidence using proxies from the past, favor a greater warming in the winter seasons over summers. All of these argue against the kind of frightening rise in temperatures predicted by the Union of Concerned Scientists for California.

More important, though, is that any application of GCM output to regions as small as California is not good scientific practice. Schemes are being developed currently by the scientific community to interpolate, reliably and soundly, GCM output down to regional scales. But logically, using GCM output to infer climate change for your state is like using a chain saw to do delicate wood carving. Additionally, the scenarios that would create such drastic climate change in the heartland of the USA in general necessarily must involve a drier climate as the UCS report does.

For every model simulation that shows California drying up, there are those that show increases in precipitation amounts for the same region under climate warming scenarios[2]. There is still a great degree of uncertainty about what the models are telling us, how to interpret what they tell us, and how they fit with current observations. To make matters even more complicated, some scientists have shown that even establishing the observational record can, in some cases, be a difficult task[3].

As for Byers' contention that a warmer world would cause more violent weather, any student who takes General Circulation Theory 101 would know that an increase in global temperatures, primarily at higher latitudes and altitudes, as most assessments show, would lead to a more placid climate.

Why? Because such a scenario would lead to weaker equator-to-pole temperature gradients, decreasing the strength of the poleward transport of energy in the atmosphere and oceans, and resulting in basically less vigorous clashes between air masses. There are abundant studies available in the literature to show there are no general trends toward increases in severe weather occurrences such as hurricanes or tornadoes.

Some are optimistic that the support for the global warming theory among the faithful scientists and activists may be about to collapse on itself[4] and it is possible that the increase in frightening rhetoric coming from this crowd through the media is a sign that they are growing more desperate.

If this is true, that is a good sign, but it must be cautioned that it took years to build up support for the theory among the general population through these scary scenarios. Since these activists tend to have a political agenda that accompanies their support for policies intended to fight global warming, they will not stop trying to implement this agenda, at least until "The Day After November 2nd".

[1] Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, D. Xiaosu, and K. Maskill (eds.) 2001: Climate Change 2001: The Scientific Basis. Cambridge University Press, Cambridge, UK and New York, NY.

[2] IPCC Reports: Climate Change 2001: Impacts, Adaptation and Vulnerability

[3] Soon, W., 2004: What is the Earth's 20th century temperature trend? June 24th,

[4] Labohm, H., 2004: The denouement is imminent. July 20th,


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