TCS Daily


Playing Politics with Climate Report Hurts Science

By Kenneth Green - November 27, 2000 12:00 AM

Less than two weeks before the U.S. presidential elections, copies of the draft summary for the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) were leaked to the media and became an instant issue in the election.

The IPCC every five years publishes a massive assessment on global climate change that becomes the central touchstone for debate of the issue.

The Second Assessment Report, published in 1995, argued that the weight of evidence suggested a "discernable" human impact upon the climate. It predicted future temperature increases of 1.8 degrees to 6.5 degrees Fahrenheit by 2100, and sea level increases of between six inches to 37 inches by then.

The Third Assessment Report itself won't be published until next year. But along with any new major report, the IPCC also publishes a "Summary for Policymakers" that condenses the contents and tries to express findings in a language suitable for moderately educated readers. It was a draft of that someone leaked to the press.

Working from more extreme "worst-case" estimates than previous reports, the draft summary suggested a higher range of potential warming by 2100, from 2.7 degrees to 10.4 degrees Fahrenheit, while suggesting that there was likely to be even higher sea levels than the mean level forecast in the second report.

The problem is that the leaked summary, unlike the main body of the Third Assessment Report, has not been peer-reviewed. Its author is anonymous, the document is created independent of the actual report, and the summary is so short that issues were overly simplified. First of all, predictions of future changes in the summary rested upon speculative scenarios that were not reviewed by technical reviewers of the main report. The new worst case scenarios enfold a panoply of assumptions, such as no mid-course programs between now and 2100; a population peak of 8.7 million in 2050; unabated global deforestation; a tenfold increase in world gross domestic product; carbon-based fuels providing most of the energy; a quadrupling of carbon dioxide emissions; a doubling of methane emissions; a tripling of carbon monoxide and volatile organic carbon emissions, and a dramatic rise in fluorocarbon levels. In addition, while the summary presents hard evidence regarding temperature readings, rain measurements, snow measurements and so on, it does so without vital contextual and qualifying information found in the report itself.

Increases in temperature, for example, are presented without pointing out that most physically observed warming since 1860 happened from 1910-1945 and most of that is attributed to non-human climate forces. The summary doesn't note that warming observed since 1860 has happened in two bursts or that twice of much of it appears as warming of nighttime low temperatures in the coldest parts of the Earth, not increases of daytime highs in the warmer parts of the Earth.

In looking at decreases in global ice, such as glaciers and icebergs, and at snowfall trends, the summary ignores that current sampling and historical measurements are too limited to be conclusive. Indeed, the report itself found glaciers in some regions are growing, while the Antarctic sea ice measurements appear stable or may have slightly increased their extent since the 1970s. The actual report even found that ice and snow aren't happening in the seasons where increased warmth has actually been observed.

As to the summary's reporting evidence of sea level rise of three to eight inches in the 20th Century, the unreported fact is the actual report assesses only three-quarters of an inch to two inches to human activity between 1910 and 1990. Sea levels have risen for almost 20,000 years by some 500 feet, and the rise in sea level did not speed up during the last century.

Finally, the summary's claim that human activities "continue to alter the atmosphere in ways that affect the climate system" is made without mentioning that this conclusion is based on still-developing theories and uncertain computer modeling, not on a measured cause-and-effect relationship. Indeed, uncertainties are still large in key modeling areas that underpin the entire claim of human causality in observed changes, such as effect of clouds and aerosols.

While computer models agree that human activities have played some role in observed 20th Century warming, individual models give very different estimates for the extent of the human role. The summary fails to report that differences found between ground-level temperature readings and high-altitude readings from balloons and satellites expose a critical weakness of the climate models used to predict future impacts. And no mention is made of evidence that documents sharper temperature shifts in the climate record from before humans existed, suggesting that recent changes could be of non-human origin.

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.

Some may have seen the leak of the summary report as a way of creating a short-term ripple in the political landscape of the United States presidential campaign. But in the long term, the 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.

Click here for Dr. Green`s full brief on this issue.
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