Global-change study could take decades.

Global-change study could take decades

Basic understanding of how human activities influence global climate probably will not improve significantly for at least a decade, six U.S. scientists agreed this week. At a briefing in Washington, D.C., for NASA officials on several recent internatinal meetings, they said much information about the Earth first needs to be collected and analyzed. But Robert E. Dickinson of the National Academy of Sciences [NAS] TOLD THE ADMINSTRATORS, "You should be prepared to [formulate policy] now, so that in 10 years when you do understand the problem, you can do something about it without having to wait another 10 years."

U.S. scientist have joined with colleagues from 40 nations to plan extensive studies of the Earth's atmosphere, biosphere and oceans from space, the air and the ground. These could begin as early as 1990. But until international satellites planned for launch in the mid-1990s return data, predictions about global warming will remain tentative, said the scientists, representing NASA, NAS, the University of New Hampshire in Durham, the University of Wisconsin-Madison and Harvard Univeristy.

Many researchers point to gases emitted by automobiles, industry and agriculture -- primarily carbon dioxide, chlorofluorocarbons, nitrous oxide and methane -- as potential contributors to a recent global warming trend [SN: 7/2/88, p.4; 4/30/88, p.282]. Thoery holds that a buildup of these gases in the atmosphere would trap heat close to the planet, causing the "greenhouse" effect: higher temperatures at the surface and in the lower atmosphere.

The scientists said they don't fully understand the factors affecting these gases, adding that sources of methane and nitrous oxide still must be identified before policies controlling uses of these chemicals can emerge. They suggested researchers can improve current understanding of global warming by:

* working together on projects encompassing their highly specialized studies

* creating global models incroporating detailed regional data rather than relying on averaged worldwide data, which can obscure important variations

* merging their models to create better ones

* verifying each other's data and interpretations.

Regardless of the effort, tools and time necessary for researchers to quantify humanity's role in climate shifts, global changes already initiated by human activities will persist for centuries, the scientists said.