NCPA - National Center for Policy Analysis

Report Summary Spins Global Warming, Says a Participant

November 12, 2001

Condensing the 700-page report of the United Nations Intergovernmental Panel on Climate Change (IPCC) into a 20-page summary requires selectivity, says Kenneth Green of the Reason Public Policy Institute -- who was an expert reviewer for the Working Group I and Working Group II volumes of the IPCC Third Assessment Report.

As with past summaries for policy-makers, the summary tends to downplay uncertainty, emphasize human culpability and generally provide only information supporting policy options favored by the United Nations -- the immediate adoption of international agreements to reduce the emissions of "greenhouse gases."

The new "Summary for Policy-Makers" suggests a higher range of potential warming by 2100 and a higher sea-level rise than previous summaries. Global average temperature in the new report is estimated to increase from a low of 1.4° centigrade to a high of 5.8° (2.5° to 10.4° Fahrenheit) by 2100.

Predicted sea-level increases under the new scenarios range from 9 to 88 centimeters (4 inches to 3 feet) by 2100.

  • However, the figures in the new summary are not based on newer, higher-quality extrapolations of recent climate trends.
  • They are based on made-up "scenarios" published in a separate "Special Report on Emission Scenarios" filtered through grossly simplified climate models after the full report had already been through expert review.
  • The new "worst case" scenario -- 10.4° and 88 cm sea-level rise -- includes questionable assumptions not reviewed by the main IPCC expert review panel.

Among other points, critics say the clear difference between ground-level temperature readings (which are increasing) and high-altitude readings from balloons and satellites (which are unchanging) reveals a critical weakness of the climate models used to predict future impacts of global warming.

Source: Kenneth Green (Chief Scientist, Reason Public Policy Institute), "Science vs. Spin: Government Warming Redux," Brief Analysis No. 378, November 12, 2001, NCPA.

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