BUENOS AIRES — The world's chief climate scientist on Tuesday disputed the U.S. government contention that cutbacks in carbon dioxide emissions are not yet warranted to check global warming.

Experts readied a report, meanwhile, saying 2004 will be one of the warmest years on record.

"The science says you've got to reduce emissions," Rajendra K. Pachauri told The Associated Press in an interview midway through a two-week international climate conference.

The Kyoto Protocol, the international accord requiring cuts in carbon dioxide, "is driven by the need to reduce emissions, and on that there is no question," said Pachauri, chairman of a U.N.-sponsored network of climatologists.

Scientists largely blame the accumulation of carbon dioxide and other "greenhouse gases" in the atmosphere for the rising temperatures of the past century.

The 10 warmest years globally, since records were first kept in the 19th century, have all occurred since 1990, the top three since 1998. Specialists here this week will issue a report saying 2004 ranks as the fourth- or fifth-warmest year recorded.

Conference delegates from dozens of nations are fine-tuning the workings of the Kyoto pact, which takes effect Feb. 16. It sets targets for 30 industrial nations -- excluding the nonparticipating United States and Australia -- to reduce emissions of six greenhouse gases, most importantly carbon dioxide, a byproduct of coal, oil and gasoline use.

The United States is a member of the umbrella U.N. treaty on climate change, and it signed that treaty's Kyoto Protocol in 1997. But President Bush renounced the Kyoto agreement in 2001, saying emission reductions would hurt the U.S. economy.

Before leaving for the annual climate-treaty talks, U.S. negotiator Harlan Watson told reporters in Washington that the United States -- the world's biggest emitter of carbon dioxide -- would eventually stop the growth in its emissions "as the science justifies." After arriving here, he said the Kyoto Protocol's approach was "not based on science."

Asked about Watson's statements, Pachauri was emphatic.

"The science says you've got to reduce emissions of greenhouse gases. The science says you've got to stabilize concentrations of greenhouse gases in the atmosphere," he said. "What may be subject to uncertainty and subject to debate is who is to reduce how much."

As chairman of the Intergovernmental Panel on Climate Change, the Indian scientist oversees the work of hundreds of specialists who regularly assess the latest research on climate change and its likely effects.

In its last major report, in 2001, the panel projected that global temperatures in the 21st century would increase by 3 to 10 degrees, depending on many factors, including how quickly and deeply gas emissions were cut back.

Warming is predicted to cause greater extremes in temperature, and possibly dry out farmlands, stir up fiercer storms and raise ocean levels, among other impacts, the panel said. At the conference Tuesday, European scientists said even an additional 2 degrees might threaten South American water supplies and reduce Asian food yields.

One of the world's leading climate institutes, the British government's Hadley Center, issued a report at the conference Tuesday on work done to narrow the uncertainties, by running many dozens more model scenarios through its supercomputers.

It said temperatures would most likely rise by an additional 5 degrees by later this century if the carbon dioxide concentration in the atmosphere doubles from its pre-industrial levels -- a probable scenario if emissions are not controlled.

Pachauri said the evidence of change is everywhere -- in the doubling of extreme weather events recorded by the World Meteorological Organization, in the melting of glaciers worldwide, and in the one-degree global temperature rise of the past century.

"The evidence is so strong, the observations so strong, it's very difficult to close your eyes to it," he said. "I was born in the mountains in India. I've seen the kinds of changes that have taken place with snow cover, with the seasons, with the extent of warming, precipitation patterns, the impact on forests."

Delegations at the conference are searching for ways to bring the United States into the Kyoto process and acceptance of mandatory reductions in gases. Besides the economic argument, Bush complained that some poor but rapidly industrializing nations, such as China and India, were not obligated by Kyoto's short-term targets.

Pachauri said he was heartened by the actions of individual U.S. states, particularly in the U.S. Northeast, to impose carbon-dioxide reductions on power plants, for example.

"I think the next round of action will only come from an acceptance of the science," he said.

Source: Associated Press