part 2
The report essentially caps a half-century-long effort to discern whether humans, through the buildup of carbon dioxide and other gases released mainly by burning fuels and forests, could influence the earth’s climate system in potentially momentous ways.
The group operates under the aegis of the United Nations and was chartered in 1988 — a year of record heat, burning forests, and the first big headlines about global warming — to provide regular reviews of climate science to governments to inform policy choices.
Government officials are involved in shaping the summary of each report, but the scientist-authors, who are unpaid, have the final say over the thousands of pages in four underlying technical reports that will be completed and published later this year.
Big questions remain about the speed and extent of some impending changes, both because of uncertainty about future population and pollution trends and the complex interrelationships of the greenhouse emissions, clouds, dusty kinds of pollution, the oceans and earth’s veneer of life, which both emits and soaks up carbon dioxide and other such gases.
But a broad array of scientists, including authors of the report and independent experts, said the latest analysis was the most sobering view yet of a century in thousands of years of relatively stable climate conditions will suddenly be replaced by a new normal of continual change.
Should greenhouse gases continue to build in the atmosphere at even a moderate pace, temperatures by the end of the century could match those last seen 125,000 years ago, in the previous warm spell between ice ages, the report said.
At that time, the panel said, sea levels were 12 to 20 feet higher than they are now due to the melting of great amounts of ice now stored, but eroding,on Greenland and in parts of Antarctica.
The panel said there was no solid scientific understanding of how rapidly the vast stores of ice in polar regions will begin to erode, so their estimates on new sea levels were based mainly on how much the warmed oceans will expand, and not on contributions from melting of ice on land.
Other scientists have recently reported evidence that the glaciers and ice sheets in the Arctic and Antarctic could flow seaward far more quickly than estimated in the past and have proposed risks to coasts could be much more imminent. But the I.P.C.C. is proscribed by its charter from entering into speculation and so could not include such possible instabilities in its assessment.
Michel Jarraud, the secretary general of the United Nations World Meteorological Organization, said the lack of clarity should offer no one comfort. “The speed with which melting ice sheets are raising sea levels is uncertain, but the report makes clear that sea levels will rise inexorably over the coming centuries,” he said. “It is a question of when and how much, and not if,” he said, adding: “While the conclusions are disturbing, decision makers are now armed with the latest facts and will be better able to respond to these realities.”
Achim Steiner, the executive director of the United Nations Environment Program, which oversees the I.P.C.C. along with the meteorological group, said society now had plenty of information on which to act.
“The implications of global warming over the coming decades for our industrial economy, water supplies, agriculture, biological diversity and even geopolitics are massive,” he said. “This new report should spur policymakers to get off the fence and put strong and effective policies in place to tackle greenhouse gas emissions.”
The warming and other climate shifts will be highly variable around the world, with the Arctic particularly seeing much higher temperatures, said Susan Solomon, the co-leader of the team writing the summary and the section of the I.P.C.C. report on basic science. She is an atmospheric scientist for the National Oceanic and Atmospheric Administration.
The kinds of vulnerabilities are very much dependent on where you are, Dr. Solomon said in a telephone interview. “If you’re living in parts of tropics and they’re getting drier and you’re a farmer there are some very acute issues associated with even small changes in rainfall — changes we’re already seeing are significant,” she said. “If you are an Inuit and you’re seeing your sea ice retreating already that’s affecting your lifestyle and culture.”
The 20-page summary is a sketch of the findings that are most germane to the public and world leaders.
The full I.P.C.C. report, thousands of pages of technical background, will be released in four sections through the year — the first on basic science, then sections on impacts and options for limiting emissions and limiting inevitable harms, and finally a synthesis of all of the findings near year’s end.
In a news conference in Paris, Dr. Solomon declined to provide her own views on how society should respond to the momentous changes projected in the study.
“I honestly believe that it would be a much better service for me to keep my personal opinions separate than what I can actually offer the world as a scientist,” she said. “My stepson, who is 29, has an utterly different view of risks than I do. People are going to have to make their own judgments.”
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The report essentially caps a half-century-long effort to discern whether humans, through the buildup of carbon dioxide and other gases released mainly by burning fuels and forests, could influence the earth’s climate system in potentially momentous ways.
The group operates under the aegis of the United Nations and was chartered in 1988 — a year of record heat, burning forests, and the first big headlines about global warming — to provide regular reviews of climate science to governments to inform policy choices.
Government officials are involved in shaping the summary of each report, but the scientist-authors, who are unpaid, have the final say over the thousands of pages in four underlying technical reports that will be completed and published later this year.
Big questions remain about the speed and extent of some impending changes, both because of uncertainty about future population and pollution trends and the complex interrelationships of the greenhouse emissions, clouds, dusty kinds of pollution, the oceans and earth’s veneer of life, which both emits and soaks up carbon dioxide and other such gases.
But a broad array of scientists, including authors of the report and independent experts, said the latest analysis was the most sobering view yet of a century in thousands of years of relatively stable climate conditions will suddenly be replaced by a new normal of continual change.
Should greenhouse gases continue to build in the atmosphere at even a moderate pace, temperatures by the end of the century could match those last seen 125,000 years ago, in the previous warm spell between ice ages, the report said.
At that time, the panel said, sea levels were 12 to 20 feet higher than they are now due to the melting of great amounts of ice now stored, but eroding,on Greenland and in parts of Antarctica.
The panel said there was no solid scientific understanding of how rapidly the vast stores of ice in polar regions will begin to erode, so their estimates on new sea levels were based mainly on how much the warmed oceans will expand, and not on contributions from melting of ice on land.
Other scientists have recently reported evidence that the glaciers and ice sheets in the Arctic and Antarctic could flow seaward far more quickly than estimated in the past and have proposed risks to coasts could be much more imminent. But the I.P.C.C. is proscribed by its charter from entering into speculation and so could not include such possible instabilities in its assessment.
Michel Jarraud, the secretary general of the United Nations World Meteorological Organization, said the lack of clarity should offer no one comfort. “The speed with which melting ice sheets are raising sea levels is uncertain, but the report makes clear that sea levels will rise inexorably over the coming centuries,” he said. “It is a question of when and how much, and not if,” he said, adding: “While the conclusions are disturbing, decision makers are now armed with the latest facts and will be better able to respond to these realities.”
Achim Steiner, the executive director of the United Nations Environment Program, which oversees the I.P.C.C. along with the meteorological group, said society now had plenty of information on which to act.
“The implications of global warming over the coming decades for our industrial economy, water supplies, agriculture, biological diversity and even geopolitics are massive,” he said. “This new report should spur policymakers to get off the fence and put strong and effective policies in place to tackle greenhouse gas emissions.”
The warming and other climate shifts will be highly variable around the world, with the Arctic particularly seeing much higher temperatures, said Susan Solomon, the co-leader of the team writing the summary and the section of the I.P.C.C. report on basic science. She is an atmospheric scientist for the National Oceanic and Atmospheric Administration.
The kinds of vulnerabilities are very much dependent on where you are, Dr. Solomon said in a telephone interview. “If you’re living in parts of tropics and they’re getting drier and you’re a farmer there are some very acute issues associated with even small changes in rainfall — changes we’re already seeing are significant,” she said. “If you are an Inuit and you’re seeing your sea ice retreating already that’s affecting your lifestyle and culture.”
The 20-page summary is a sketch of the findings that are most germane to the public and world leaders.
The full I.P.C.C. report, thousands of pages of technical background, will be released in four sections through the year — the first on basic science, then sections on impacts and options for limiting emissions and limiting inevitable harms, and finally a synthesis of all of the findings near year’s end.
In a news conference in Paris, Dr. Solomon declined to provide her own views on how society should respond to the momentous changes projected in the study.
“I honestly believe that it would be a much better service for me to keep my personal opinions separate than what I can actually offer the world as a scientist,” she said. “My stepson, who is 29, has an utterly different view of risks than I do. People are going to have to make their own judgments.”
- bill 2-02-2007 4:33 pm