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E-brief 105

Mopping up After a Leak: Setting the Record Straight on the "New" Findings of the Intergovernmental Panel on Climate Change (IPCC)

Kenneth Green
October 1, 2000

Every five years, the Intergovernmental Panel on Climate Change publishes a massive report on global climate change. These "Assessment Reports" become the central touchstone of the debate over climate change, laying out a consensus version of what is known, what is still uncertain, and how various actions might or might not cause changes in future climate conditions.

The last such publication was the IPCC's "Second Assessment Report (SAR),"published in 1995. The 1995 SAR argued that the Earth's climate was changing in ways that seemed unlikely to be of non-human origin, and that the weight of evidence suggested a "discernable" human impact upon the climate. Predicted future temperatures in the SAR ranged from 1 °C to 3.5 °C (1.8 °F to 6.5 °F) degrees centigrade by 2100, and sea level increases of 15 to 95 cm in the same timeframe.

The 1995 report is about to be supplanted by the IPCC "Third Assessment Report, or TAR, to be published early in 2001. The first volume of the TAR, the product of IPCC's Working Group 1 (WG1) reviews the massive body of climate change literature, and attempts to present a consensus view of the current understanding of climate change. This report was reviewed by a panel of experts in late 1999, was subsequently reviewed by governmental entities, was revised according to feedback, and is now undergoing "final government review." After a last round of revisions based on the final government review (which, theoretically will not alter any of the scientific conclusions of the report as it emerged from expert review), the TAR will be published in early 2001.

When the IPCC publishes a new major report, it also publishes a derivative document called the "Summary for Policymakers" (or Summary). These summaries attempt to condense the contents of the IPCC's full Assessment Report, and express findings in a language suitable for moderately educated readers.

Less than two weeks before the U.S. Presidential elections, copies of the draft Summary for Policymakers based on the Third Assessment Report were leaked to the Associated Press and other media commentators. The draft Summary became an instant issue in the election.

Working from more extreme �worst-case' estimates than previous IPCC reports, the Summary suggests a higher range of potential warming by 2100, and higher sea-level rise as well. Global average temperature in the new Summary is modeled to increase from 1.5 to 6.0 degrees Centigrade by 2100 (2.7 to 10.4 degrees Fahrenheit). Predicted sea-level increases under the new scenarios range from 14 to 80 cm by 2100.

But media coverage of the Summary lacks contextual information needed to allow people to decide whether the report was credible. The genesis of the Summary was not explained, and the "findings were not put in context with regard to either the previous assessment report, or the main body of the more scientifically rigorous and more carefully qualified Third Assessment Report.

Climate change is a concern worthy of serious attention, and the best quality scientific research that humanity can muster. It is an issue of great complexity, in which fine details of interpretation, and underlying assumptions are indispensable if sound policy is to be derived from sound use of scientific information.

The purpose of this document is to add some context and balance to the discussion, and to correct some of the mistaken impressions that recent news coverage of the leaked IPCC draft Summary for Policymakers may have created.

1. Predictions of future changes rest upon speculative scenarios that were not reviewed by technical reviewers of the main report.

The claims regarding the potential increase in global average temperatures and sea levels in the year 2100 are based upon "scenarios" about the future that enfold a panoply of assumptions about global development patterns, population growth, energy sources, economic development, technological change, and so on:

2. The Summary for Policymakers presents findings devoid of vital contextual information.

When discussing the findings of how the Earth's climate has changed in recent years, the Summary for Policymakers presents hard evidence regarding temperature readings, rain measurements, snow measurements, and so on. But the Summary presents this information without vitally important contextual and qualifying information found in the body of the IPCC report:

3. The leaked "Summary for Policymakers" is not peer-reviewed, the author is anonymous, the document is created independently of the actual Assessment Report, and the Summary is so short that issues are overly simplified.


News coverage of the recently leaked "Summary for Policymakers" from the pending Third Assessment Report of the Intergovernmental Panel on Climate Change lacks information vital to putting the leaked document in meaningful perspective.

Specifically, the leaked report:

The forthcoming Third Assessment Report of the Intergovernmental Panel on Climate Change will serve as the central touchstone of climate change debate for the next five years. Climate change is a serious and important subject, and concerns about rapid changes in climate � whatever the cause might be — should not be treated lightly. Accuracy in the understanding of the underlying science is equally critical, and should not be misrepresented or politicized by partisans of any particular control approach.

Activities which weaken the credibility of the TAR impede not only the search for knowledge, but insure greater divisiveness in the debate over whether the report represents a scientific consensus, or is a document biased by political forces outside of the scientific process of discovery.

The leak of the Summary report of the IPCC Third Assessment Report may be seen, by some, as a way of creating a short-term ripple in the political landscape of the United States Presidential campaign. But in the long term, this leak can only harm the search for a consensus statement of knowledge, and the search for appropriate responses to the risks posed by climate change.

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Dr. Kenneth Green is Director of the Environmental Program at Reason Foundation.

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