TCS Daily

Politics foils objective U.N. Climate Change Report -- again

By Kenneth Green - February 26, 2001 12:00 AM

Once again, climate change is in the news, as the United Nations Intergovernmental Panel on Climate Change (IPCC) has released a "Summary for Policymakers" based on the massive second volume of its "Third Assessment Report" on climate change.

IPCC Volume 2 picks up where the Volume 1 left off, asking how temperature increases predicted in Volume 1 might lead to climate changes in the future. The new Volume 2 Summary (all that's been released to date) raises the specter of coastal inundation; violent weather; droughts; increased spread of mosquito-borne illnesses; crop failures; and more.

In fact, there is evidence that the Earth's atmosphere has been heating up a bit for the past 150 years, and there is good reason for people to be concerned about a changing climate -- so far as a changing climate can produce such extreme conditions -- delicate ecosystems, agriculture, transportation systems, coastal structures could face additional risk.

But for environmental policies to provide the best return on investment, they have to be prioritized against all the other environmental concerns facing individuals and society, and that prioritization requires scientifically rigorous risk characterization. Unfortunately, the 19-page Volume 2 Summary fails several tests of scientific rigor, such as substantiating assumptions, using sound statistics to indicate certainty, and using meaningful peer-review. Unlike the 1,000 page underlying report, the Summary was written by only a few governmental officials; was reviewed only by a small selection of the original authors, and was not subject to expert review.

The biggest failing of the Volume 2 Summary is its tendency to exaggerate the scientific certainty of the predictions it makes. Though specific words meant to convey certainty are paired with numerical estimates of certainty (high confidence, for example, is supposed to imply greater than 95 percent certainty), the assignment of these "confidence" terms and numbers is an exercise in nearly pure subjectivity. The Volume 2 Summary describes how terms like "very high confidence" are derived as follows: "In this Summary for Policymakers, the following words have been used where appropriate to indicate judgmental estimates of confidence (based upon the collective judgment of the authors using the observational evidence, modeling results, and theory that they have examined..."

The Volume 2 also fails to explain that its predictions are based on highly criticized modeling of dubious worst-case scenarios. The predictions made in the new report are not based on independent observation and extrapolation of real-world trends, but are based upon an estimated range of predicted warming from the Volume 1 report - a controversial and dubious estimate that itself is based on questionable assumptions from a third report. Even were it not for these pre-existing problems, the computer models used in the Volume 2 effort are of questionable value. According to a Science news brief from June 2000, Jerry Mahlman, director of NOAA's Geophysical Fluid Dynamics Laboratory, observes that when regional climate models such as those used in the new IPCC report try to incorporate external factors such as population and economic growth rates, "the details of future climate recede toward unintelligibility." Climate modeler Filippo Giorgi, of the Abdus Salam International Center for Theoretical Physics, observes that regional climate models of the sort used by the WGII authors are of limited value: "For the most part, these sorts of models give a warning, but they tend to give very different predictions, especially at the regional level, and there's no way to say one should be believed over another."

Finally, the Volume 2 Summary lumps all possible types and causes of climate change together, whether it is of human origin, solar origin; whether it is warming, or whether it is cooling. But current understanding in the mainstream scientific literature only ascribes half of the observed warming since the 1970s to human activity - a critical distinction for policymaking. Without specifying how much of which impacts are predicted to be of human origin, the Volume 2 Summary deprives policymakers of information needed to determine appropriate action.

While everyone is rightly concerned about prospective changes in climate, the devil is in the details. With finite resources available to use in the human search for safety, some basic ranking of investments is imperative to be sure we get the best return on investment. In the realm of climate-change policy, such ranking becomes impossible when politicized portrayals of the state of scientific knowledge are passed off as the best that science has to offer. The latest IPCC report Summary continues a pattern of publishing Summary reports that distort more than they reveal, and will misinform policymakers more than it will inform them.

Information on the IPCC reports can be found at (


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