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 Published by the American Geological Institute
Newsmagazine of the Earth Sciences

September 2000

News Notes
 Climate Change

Assessing climate change: Fair warning or scare tactic?
In June, the U.S. Global Change Research Program released a draft of the National Assessment on Potential Consequences of Climate Variability and Change for public comment. As of late July, more than 200 comments had been collected by the assessment team’s lead authors — Jerry Melillo, Anthony Janetos and Thomas Karl — who will prepare a final report to go to Congress early this fall.

In 1990, President Bush signed legislation mandating the formation of a team that would draw together climate researchers from across the nation to begin an ongoing scientific discussion on climate changes, their impact and how Americans might have to adapt to those changes. The report looks at climate by geographic region and sectors: water, agriculture, human health, coastal areas and marine resources. Many of the forecasted scenarios are region specific, but overall the assessment points to an increase in the average temperature of between 5 and 10 degrees Celsius over the next 100 years and suggests drastic changes in precipitation patterns and soil moisture.

     Precipitation patterns could change 
     dramatically over the next century. Alternating periods 
     of drought and deluge could cause problems across 
     the U.S.

Its authors are trying to convey that the report does not make predictions — its purpose is to illustrate potential situations. “This is a first look at what adaptation options might be,” says Anthony Janetos, co-chair of the assessment and director of the World Resources Institute. “We’ve been careful to say that the assessment has not tried to predict all of the details of the future.” Thomas Karl of NOAA’s National Climate Data Center also co-chaired the assessment. “We’re playing the ‘What if...?’ game,” he says, “Given the science available today, we’re trying to figure out how climate may change.”

Two climate models were used to create plausible scenarios for regional climate change across the United States — a very bold endeavor in the eyes of many scientists. Fred Singer of the Science and Environmental Policy Project in Fairfax, Va., is one scientist who believes models cannot stand up as scientific evidence for climate change. Singer, an avid activist on his climate views, believes that models are necessary for making predictions. However, he says, “if a model cannot predict the past, then you can’t expect it to predict the future. When the models disagree, which one should you believe? I believe that models will improve, but they aren’t there now.”

The authors acknowledge this concern, but defend the process nonetheless. “The fact that the models differ is not a statement on the assessment process, but rather a statement on where the science is now,” Janetos says.

A self-described “modest skeptic” of large and complicated models is Robert Frosch who teaches in the Science, Technology and Public Policy Program at Harvard University’s Kennedy School of Government. Frosch, who thought the assessment was “pretty heavy on doomsday,” questions one of the assessment’s basic assumptions: “Suppose we could dial carbon dioxide back? Things wouldn’t necessarily go back in the same pattern.” He wonders why cutting back carbon dioxide is commonly considered the only way to curb climate change.

Others remain more focused on the present and are satisfied that something is being done. “There is a lot of room for scientific discussion and disagreement, but unless we start that process then it’s even more difficult for policy-makers and the public to understand,” says Dan Cayan, director of Climate Research at Scripps Institution of Oceanography. Considering the possible consequences of accelerated warming, Cayan believes that the assessment is a proactive step in the best interest of the nation. “I am not a card-carrying global change guy, I’m just telling you what I see,” he says. “The balance of evidence really points to anthropogenic warming.”

Charles Keller, director of the Institute for Geophysics and Planetary Physics at Los Alamos National Laboratory, acknowledges the controversy that surrounds the document: “Not only does the assessment talk about change, but it makes predictions. You ask yourself, ‘How do they know that?’” He does not consider the assessment to be conservative but believes that, barring something unknown, any temperature rise will probably be near the lower end of the assessment’s range.

While the scientific community was encouraged to share all comments, Keller warns against taking the matter lightly: “I think people who discount this as a political statement meant to scare people don’t do justice to the report. Some of these things could happen.”

Laura Wright

The public comment period ended Aug. 11 but the draft assessment can still be found at

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