By CHARLES J. HANLEY

The Associated Press

NAIROBI, Kenya -- A long-awaited report by an international scientific network will offer "much stronger" evidence of how man is changing Earth's climate, and should prompt reluctant governments into action against global warming, the group's chief scientist said Monday.

The upcoming, multivolume U.N. assessment -- on melting ice caps, rising seas and authoritative new data on how the world has warmed -- may provide "just the right impetus to get the negotiations going in a more purposeful way," Rajendra K. Pachauri told The Associated Press midway through the annual two-week U.N. climate conference.

The Indian climatologist is chairman of the Intergovernmental Panel on Climate Change, a global network of some 2,000 scientists that regularly assesses research into how carbon dioxide and other heat-trapping gases produced by industry and other human activities are affecting climate.

In its pivotal Third Assessment in 2001, the panel concluded that most global warming -- temperatures rose an average 1 degree in the past century -- was likely the result of such manmade greenhouse gases.

In its Fourth Assessment, to be issued in installments beginning in February, "there's much stronger evidence now of human actions on the change in climate that's taken place," Pachauri said.

The 1997 Kyoto Protocol requires 35 industrialized nations to reduce their greenhouse emissions by 5 percent below 1990 levels by 2012. The United States and Australia are the only major industrial nations to reject Kyoto. President Bush contends such emissions cuts would harm the U.S. economy.

At the U.N. conference here, Kyoto parties are discussing what kind of timetables and quotas should follow that pact's expiration in 2012.

They also are weighing ways to draw the United States, the world's biggest carbon dioxide emitter, into a mandatory system of emissions caps. Many look toward the scientists' upcoming assessment for support.

"It's bound to have a major impact," Pachauri said.

He said the detailed document will offer significantly more evidence on sea-level rise, the melting of glaciers and the growing scarcity of water. He didn't discuss those details, since the Fourth Assessment Report is still in the draft stage. But it is likely to cite such recent research findings as:

World temperatures have risen to levels not seen in at least 12,000 years, propelled by rapid warming the past 30 years.

Greenland's ice mass has been melting at what NASA calls a "dramatic" rate of 41 cubic miles per year, far surpassing the gain of 14 cubic miles per year from snowfall.

The levels of oceans, expanding from warmth and from land-ice runoff, have risen at a rate of about 2 millimeters a year between 1961 and 2003, and by more than 3 millimeters a year in 1993-2003.

Pachauri said increasingly powerful supercomputers allow scientists to run more accurate models of future climate. The match between what the computer models have predicted and what is actually happening to the climate has become "much, much sharper," he said. This has allowed his panel to refine its range of scenarios for 21st-century climate.

In the 2001 assessment, the U.N. network projected temperatures in this century would rise between 2.5 and 10.4 degrees, depending on many factors, including whether governments move quickly to rein in emissions. In the upcoming report, "we probably have a narrowing of ranges," Pachauri said. "Some of the uncertainties are being reduced."

Further warmth of even 1 or 2 degrees would tend to shift climate zones, disrupting agriculture and ecosystems, and producing more extreme weather events, scientists say.

Pachauri credited the ever-deeper ice-core samples taken in Antarctica and Greenland for allowing scientists to look further back at ancient atmospheres. This "gives you a solid perspective on what human beings have done to Earth's climate," he said.

Citing growing public acceptance of the science of climate change, Pachauri indicated he believed the United States would eventually accept emissions caps. "Democratic governments will have to take into account the views of the public," he said.