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'Much Stronger' Signs Of Human Role In Warming

NAIROBI, Kenya (AP) _ An authoritative new U.N. assessment of how Earth's climate is changing - its temperatures rising, polar ice melting, oceans expanding - should have ``a major impact'' on the political debate over dealing with global warming, the world's chief climate scientist says.

The upcoming report by an international scientific network ``might provide just the right impetus to get the negotiations going in a more purposeful way,'' said Rajendra K. Pachauri, chairman of the group, the Intergovernmental Panel on Climate Change.

The Indian climatologist was interviewed Monday, midway through the annual two-week U.N. climate conference.

His global network of some 2,000 climate and other scientists regularly evaluates the state of research into how carbon dioxide and other heat-trapping gases produced by industry and other human activities are affecting the climate.

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

In its Fourth Assessment, to be issued in installments beginning next February, ``there's much stronger evidence now of human actions on the change in climate that's taken place,'' Pachauri told The Associated Press.

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 the emissions cuts would harm the U.S. economy.

Here at the Nairobi conference, 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 heavily 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 may likely 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 Fahrenheit, 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 farther 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.

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