Climate change Qs & As


As Earth warms, Science editor-in-chief and others urge America to remember the world's poor

WASHINGTON, DC--Island and river-delta communities are beginning to vanish beneath the waves as the Earth warms, ice melts and sea levels rise worldwide. Native Inuit fishermen are falling through thinning Arctic ice they've traversed many times before. Climate change reportedly claimed some 150,000 lives in 2000 and sickened many others, according to the World Health Organization.

What climate conditions await our children and grandchildren--from Louisiana to India, and from London to Africa?

"By mid-century, millions more poor children around the world are likely to face displacement, malnourishment, disease and even starvation unless all countries take action now to slow global warming," said Michael Oppenheimer, part of an all-star panel convened Tuesday, 15 June by AAAS, the world's largest general science society, and its journal, Science.

"Mansions along the Hamptons of Long Island, New York, can be rebuilt further inland when the beaches erode," said Oppenheimer, professor of geosciences and international affairs at Princeton University. "But imagine the difficulties faced by families in Bangladesh. An area where about 8 million people now live would be underwater if global sea level were to rise half a meter. Where are they going to go?"

Science Editor-in-Chief Donald Kennedy agreed.

"It should go without saying that the vulnerability of the world's poor will be multiplied many-fold if global warming causes significant melting of one or both of the polar ice sheets," Kennedy said. "Yet, exacerbation of poverty around the world, whether from flooding, reduced crop yields or increased prevalence of asthma, diarrhea, malaria or other illnesses--is part of the climate-change story that hasn't really been told. That is why it's important to make the science underlying climate change accessible to policymakers in parts of the world, like the United States, where much of the source of the problem lies."

These and other perspectives on global warming emerged today during a free, public conference, "Qs and AAAs About Global Climate Change," organized by Kennedy and Albert Teich, director of Science & Policy for AAAS (the American Association for the Advancement of Science). Experts including Nobel Laureate in Chemistry Sherwood Rowland of the University of California, Irvine, shared their latest research findings and best temperature projections at the conference.

In this way, the U.S. researchers took first steps toward responding to a 9 January Science article by Sir David King, the United Kingdom's Chief Scientific Adviser, which challenged America to better control greenhouse gases. (Reference:

Oppenheimer urged scientists from all countries to join together to identify the "critical thresholds" that may trigger catastrophic melting of the polar ice sheets, which would boost sea levels, flooding islands and coastal regions.

The authoritative Intergovernmental Panel on Climate Change (IPCC), established by the World Meteorological Organization and the United Nations Environment Programme, has estimated that, between 1990 and 2100, temperatures will rise between 1.4 and 5.8 degrees Celsius (2.5 to 10.4 F). Already, the IPCC has reported, temperatures have increased between 0.4 and 0.8 degrees C--or, an increase of about 1 degree F to date, with most of the warming happening over the most recent decades.

But, David Battisti, the Tamaki Professor of Atmospheric Sciences at the University of Washington and Director of the University's Earth Initiative, warned that "current models used to project the climate 100 years into the future may be grossly underestimating the amount of warming that is going to happen as a result of greenhouse gases."

Scientists generally agree that temperatures are rising as a result of human activities such as fossil-fuel burning, which releases carbon dioxide and other heat-trapping greenhouse gases. This warming has caused glacial melting and subsequent increases in sea levels worldwide of 10 to 20 centimeters, or 4 to 8 inches.

According to Oppenheimer, models project that if Greenland temperatures rise by another 3 degrees C, complete melting of the Greenland ice sheet would eventually result. "If the West Antarctic ice sheet becomes unstable, global sea level would rise about 5 meters and as much as seven meters if the Greenland ice sheet melts," he said. Although the sea level rise would largely occur in later centuries, these outcomes could be set in place within the current century.

"We're on the verge of a very large global-warming event," Battisti warned. "Without limits on emissions, carbon dioxide could increase by three-fold in 150 years, reaching levels that were last seen 35 million years ago."

Would melting polar ice destabilize ocean circulation, pushing the relatively warm Gulf Stream southward and causing the North Atlantic to freeze--as depicted in Hollywood's latest disaster movie, "The Day After Tomorrow"? Probably not, said Battisti. "One hundred years from now, the amount of carbon dioxide in the atmosphere is likely to be at least two times greater than today," he said. "Any localized cooling that might occur in the North Atlantic will be overwhelmed by a very large warming caused by a large increase in the greenhouse effect."

Moreover, greenhouse gases are warming the Earth faster than aerosols like dust can mask them, said Joyce E. Penner, professor of atmospheric, oceanic and space sciences at the University of Michigan. Various types of aerosols--from soot and dust to sulfur--can either cool or warm the climate, she explained. Warming is associated with absorbing black carbon emissions such as soot, while non-absorbing aerosols are tied to cooling, which scientists call "negative forcing."

"In the long term, greenhouse gas effects are not going to be masked by aerosols," Penner said, debunking a popular myth related to climate change. "But in the short term, we have a problem predicting what aerosols do to the climate. The best current aerosol models give a cooling force, which is larger than we can explain. This must be balanced by other effects that are not properly accounted for in climate models. But eventually, warming caused by greenhouse gases will overwhelm any aerosol-related cooling."

Many scientific questions about climate change remain, Kennedy acknowledged, but policymakers and the public must take action now.

"We're in the middle of a large, uncontrolled experiment on the only planet we have," Kennedy said, reiterating comments set forth in an editorial published 11 June in Science. "It's only natural that there is lively disagreement among scientists about what the future may hold," he added, referring to uncertainties associated with physical climate-change models, which were the focus of the AAAS conference. "Unfortunately, these disagreements have often persuaded thoughtful newspaper readers that since the scientists can't agree, the issue can safely be ignored."

Continued warming is expected to dramatically increase flooding, affecting communities and economies around the world, King and others have reported. Consequently, "millions more people around the world may in future be exposed to the risk of hunger, drought, flooding, and debilitating diseases such as malaria," King noted, citing the U.K.'s Flood and Coastal Defences Report. "Poor people in developing countries are likely to be most vulnerable." Stabilizing carbon dioxide levels at around 550 parts per million by 2100 "could reduce flooding frequency by some 80 to 90 percent along the most vulnerable parts of the Indian and Bangladesh coastlines," King said.

Alan I. Leshner, AAAS CEO and executive publisher of Science, will join Science Editor-in-Chief Kennedy in co-hosting the 15 June conference. Other speakers will include Thomas Crowley, Duke University; Richard Alley, Pennsylvania State University; Daniel Schrag, Harvard University; Jerry Meehl, National Center for Atmospheric Research; Lonnie Thompson, Ohio State University; and Chris Field, Carnegie Institution of Washington.

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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