Report links man-made pollution to global warming

New evidence shows that man-made pollution has "contributed substantially" to global warming and that the earth is likely to get a lot hotter than previously predicted, concludes the Intergovernmental Panel on Climate Change.\nA United Nations organization, IPCC's findings are expected to widely influence climate debate over the next decade. The report's summary, a copy of which was obtained by The Associated Press, was being distributed to governments around the world, according to Neil Leary, head of the Technical Support Institute of the IPCC. The Institute helps the scientists at the IPCC direct its reports. \nThe report predicts the extent of change of global temperatures over the next century and will be reviewed in a plenary session in Shanghai in January 2001. There were two previous reports.\n"This report says what the previous one did, but says it loudly," said Ben Brabson, a physics professor. "In 1990, scientists didn't know about sulfur and its (cooling effect) on the climate. Hence, they predicted an overall rise in temperatures without setting the sulfur dioxide limits."\nIn 1995, sulfur dioxide was widely believed to reduce global temperatures considerably, and scientists' estimates of temperatures were more conservative.\n"Now we've come a full circle," Brabson said. "Since the sulfur dioxide in the air has been brought down substantially to combat acid rain, its cooling effect has been mitigated. So we are estimating the same temperatures as in 1990."\nIn the IPCC's new assessment, "there is stronger evidence," than ever before on the human influence on climate, and that it is likely that man-made greenhouse gases already "have contributed substantially to the observed warming over the last 50 years."\nAnd the scientists said if greenhouse emissions are not curtailed, the earth's average surface temperatures could be expected to increase from 2.7 to nearly 11 degrees Fahrenheit by the end of this century -- substantially more than estimated in its report five years ago.\nIt attributes the increase -- from a range 1.8 to 6.3 degrees Fahrenheit warmer in the 1995 assessment -- mainly to a reduced influence now expected to be played by sulfate releases from industry and power plants.\nKevin Trenberth, head of climate analysis section at the National Center for Atmospheric Research, said global warming has to do with greenhouse gas emissions. \n"What this report is unambiguously saying is that global warming is a real problem and it is with us and we are gong to have to take this into account in our future planning," he said. \nThe report has been the outcome of observations during several intensely warm years. \n"After replicating computer records of decades of climate observations and recording the temperature changes the earth has undergone due to human activity, the report attributes two-thirds of the warming to greenhouse gas emissions," he said.\nMichael Schlesinger, a climatologist and professor at the University of Illinois at Champaign-Urbana, wrote a paper on the issue of global warming and is widely considered an expert in his field. He said human factors, volcanic activity and the sun contribute to the overall warming effect. \n"Information about some natural climatic variables is presently incomplete, those findings may alter the assessment," he said.\nSchlesinger's work had revealed that the cooling effect, contributed by sulfate aerosols, (the sulfate nucleii that attracted water droplets and then scattered radiation) was balancing the warming in the atmosphere, but with the reduction of sulfur dioxide in the atmosphere to reduce acid rain. \n"There is an imminent threat of warming and efforts toward reducing warming must continue," he said.\nThree years ago, industrialized nations tentatively agreed to curtail the release of greenhouse gases -- mainly carbon dioxide from burning fossil fuels -- to below 1990 levels as a first step to address global warming. But none of the major industrial countries has yet ratified the agreement.\nThe IPCC panel's summary of a voluminous technical report covering 14 chapters attempts to provide the most current state of scientific understanding of the climate system and potential for future warming.\n"Emissions of greenhouse gases and aerosols due to human activities continue to alter the atmosphere in ways that affect the climate system," the report said. "Various findings of the last five years have reinforced the IPPC's 1995 determination that climate change warrants top-level attention by government policy makers."\nThe Associated Press contributed to this report.