The Meaning of Global Warming Claims
On September 30, Richard S. Lindzen, the Alfred P. Sloan professor of meteorology at MIT, gave a presentation “On the Meaning of Global Warming Claims” at a congressional briefing sponsored by the Cooler Heads Coalition. Lindzen is one of the leading critics of the claim that increasing atmospheric levels of greenhouse gases have “ominous implications” for mankind or the environment.
He began the presentation with a quick climate history of the last one hundred years and what that history means within the context of this debate. The warming during this period, said Lindzen, is concentrated in two periods, 1919-1940 and 1976-1986. The Earth cooled between these warming periods, and since 1986 there has been no significant warming.
A doubling of atmospheric concentrations of carbon dioxide, according to model predictions, would increase the temperature by about 1.5 to 4.5 degrees Celsius. We are already more than halfway towards a doubling of carbon dioxide, which has increased from about 280 parts per million to about 370 ppm. If all the warming in the past century was due to manmade carbon dioxide emissions, said Lindzen, it would mean that the climate is not very sensitive to changes in greenhouse gases and that pronounced warming is unlikely.
Lindzen argued that, “If most current climate models, which predict about 4 degrees C warming for a doubling of CO2, are correct, then man has accounted for 3 – 4 times the observed warming over the past century with some unknown processes of unprecedented magnitude canceling the difference. Predictions for the future assume that these unknown processes will disappear.”
The real problem in the global warming debate, Lindzen said, isnt so much the disagreement between scientists. Indeed, “There really is relatively little disagreement among scientists on a number of basic aspects of this issue.” The problem has to do with how the basic facts are communicated to the public. Scientists who insist on pointing out the “profound disconnect between scientific meaning of common statements and the public interpretation,” are marginalized as “skeptics.”
Rather than trying to solve this communication problem, many scientists, as well as environmental advocacy groups and politicians, have decided it would be easier to exploit it and have become quite adept at doing so. Lindzen argued that probably the best example of how a statement can mean different things to scientists and the public is from the Intergovernmental Panel of Climate Changes Second Assessment Report. It stated, “The balance of evidence suggests a discernible human influence on global climate.” To a scientist this statement does not imply that there is a problem, yet it was the “smoking gun” for Kyoto.
Lindzen also presented examples of where the scientific consensus is actually the opposite of what is presented in public. It has often been claimed that global warming will lead to increased storminess in the extratropics, but in fact, theory and observational evidence does not support this claim and there is general agreement on this in the scientific community.
Finally, Lindzen noted that although many environmental advocates and politicians claim that Kyoto would “solve” global warming, scientists agree that, “Complete adherence to Kyoto will have no significant impact on climate, regardless of what one believes about climate sensitivity.”
Land Cover Changes Contribute to Climate Change
A NASA funded study, appearing in the August 2002 issue of Philosophical Transactions of the Royal Society of London, has found that land use changes may be at least as important as greenhouse gas emissions in accounting for climate change. Growing urban areas, deforestation and reforestation, agriculture and irrigation can have strong influences on regional temperatures, precipitation and large-scale atmospheric circulation.
Different land surfaces have different effects on how the Suns energy is distributed back to the atmosphere. Changes in land cover can significantly affect temperature and other climate variables. “Our work suggests that the impacts of human-caused landcover changes on climate are at least as important, and quite possibly more important than those of carbon dioxide,” said Roger Pielke, Sr., an atmospheric scientist at Colorado State University, and lead author of the study. “Through landcover changes over the last 300 years, we may have already altered the climate more than would occur associated with the radiative effect of a doubling of carbon dioxide” (www.sciencedaily.com, October 2, 2002).