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Profile: John P. Holdren
John P. Holdren was a participant or observer in the following events:
The UN’s Intergovernmental Panel on Climate Change issues a summary of its fourth report concluding for the first time that global warming is “unequivocal.” The authors of the report also conclude that there is a 90 percent likelihood that greenhouse gases produced as a result of human activities have been the main cause of global warming since 1950. In its last report (see January 22, 2001), the panel made the same assessment, but with a confidence level of only 66 to 90 percent. The 20-page summary, meant for policymakers, will be followed by four technical reports that will be completed and published later in the year. The panel’s conclusions are based on “a three-year review of hundreds of studies of past climate shifts; observations of retreating ice, warming and rising seas, and other changes around the planet; and a greatly expanded suite of supercomputer simulations used to test how the earth will respond to a growing blanket of gases that hold heat in the atmosphere,” the New York Times reports.
Partial list of conclusions -
Global temperatures will increase 3.5 to 8 degrees Fahrenheit if carbon dioxide concentrations in the atmosphere attain levels twice that of 1750, before the Industrial Revolution.
Concentrations of carbon dioxide have reached a level not seen during the last 650,000 years, and the rate of increase is beginning to accelerate.
Even a moderate warming of the global climate would likely result in significant stress to ecosystems and change longstanding climate patterns that influence water supplies and agricultural production.
Sea levels will likely rise between 7 and 23 inches by 2100 and continue rising for at least the next 1,000 years.
“It is very likely that hot extremes, heat waves, and heavy precipitation events will continue to become more frequent.”
The panel expects that precipitation will increase at higher latitudes, while rainfall will likely decrease at lower latitudes. Semi-arid subtropical regions could see 20 percent less rain.
Oceans will absorb billions of tons of carbon dioxide which will form carbonic acid, thus lowering the pH of seawater and harming certain kinds of marine life such as corals and plankton.
If the level of greenhouse gases continues to grow, average temperatures by the end of the century could reach temperature not seen since 125,000 years ago when ocean levels were 12 to 20 feet higher than they are now. Much of that extra water is currently locked in the ice sheets of Greenland and Antarctica, which are beginning to melt. While there is evidence that the glaciers and ice sheets in the Arctic and Antarctic could flow seaward far more quickly than current estimates predict, the climate change panel did not include this in its assessment because it is forbidden by its charter to engage in speculation. According to Michel Jarraud, the secretary general of the United Nations World Meteorological Organization, “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. It is a question of when and how much, and not if.”
The harmful consequences of global warming can be lessened if governments take prompt action.
Achim Steiner, executive director of the United Nations Environment Program, which administers the panel along with the World Meteorological Organization, says: “In our daily lives we all respond urgently to dangers that are much less likely than climate change to affect the future of our children. Feb. 2 will be remembered as the date when uncertainty was removed as to whether humans had anything to do with climate change on this planet. The evidence is on the table.”
John P. Holdren, an energy and climate expert at Harvard, who is the president of the American Association for the Advancement of Science, says the report “powerfully underscores the need for a massive effort to slow the pace of global climatic disruption before intolerable consequences become inevitable.… Since 2001, there has been a torrent of new scientific evidence on the magnitude, human origins and growing impacts of the climatic changes that are under way. In overwhelming proportions, this evidence has been in the direction of showing faster change, more danger and greater confidence about the dominant role of fossil-fuel burning and tropical deforestation in causing the changes that are being observed.”
Richard B. Alley, one of the lead authors and a professor at Pennsylvania State University, says: “Policy makers paid us to do good science, and now we have very high scientific confidence in this work—this is real, this is real, this is real. The ball’s back in your court.” [Intergovernmental Panel on Climate Change, 2/2/2007 ; New York Times, 2/3/2007; Independent, 2/3/2007]
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