Buying time in the war on global warming.

Buying time in the war on global warming 

President Bush has received a birthday present three months early. Two climate researchers reported this week that the world will suffer little by waiting a decade to begin reducing emissions of greenhouse gases -- a finding that apparently justifies the President's go-slow policy on the issue of gloal warming.

Many experts, however, view the new study as too simplistic to serve as a guide for political decisions. "It's hard to call this a piece of work that could give you high confidence in whether you could wait 10 years or not," says Warren M. Washington, a computer modeler at the National Center for Atmospheric Research in Boulder, Colo.

The new results emerged from a series of climate simulations performed by Michael E. Schlesinger and Xingjian Jiang of the University of Illinois at Urbana-Champaign, who describe the work in the March 21 NATURE. The two researchers used a simple climate/ocean model to forecast how global temperature would respond to different emissions-reduction scenarios. They chose the simple model instead of a complex general-circulation model because the larger one would have required thousands of hours of computing time, Schlesinger told SCIENCE NEWS.

Many environmentalists and scientists have lobbied for a quick international response to limit greenhouse gas emissions, insisting that immediate action is necessary in order to forestall dramatic climate warming. But the new simulations present a cooler conclusion. They suggest that the world's nations can wait 10 years before reducing greenhouse gas emissions and still obtain at least 95 percent of the benefits derived from immediate cuts in emissions. Because a decade's delay would incur such a minor penalty, Schlesinger and Jiang suggest that researchers have time to launch a "crash program" to resolve some critical scientific questions on climate change.

Other climate modelers call that picture far too rosy, arguing that the Illinois model doesn't include the kind of climate factors that could drastically speed the pace of global warming. For example, a warming of the ocean's surface layer might slow the currents that carry heat down into the deep ocean -- an effect that would accelerate a temperature rise. But this kind of feedback effect, says Washington, is not easily incorporated in the simple type of climate model used by Schlesinger and Jiang.

Even complex models that do include such feedback effects may not simulate them accurately, notes climatologist James Hansen of NASA's Goddard Institute for Space Studies in New York City. Regardless of the model used, therefore, scientists cannot forecast sudden "nonlinear" reorganizations in the climate system, he says. "That makes it very prudent to be very careful about how hard we're pushing the climate system, because we just don't know when it might respond in a very non-linear way," Hansen says.

If nations defer action, they will have to adopt much more painful emission-reducing programs in the future, he contends.