Environmental Factor, July 2008, National Institute of Environmental Health Sciences
Nobel Winner Reviews the Science of the Greenhouse Effect
By Eddy Ball
One of the pioneers of global warming and greenhouse effect research, F. Sherwood Rowland, Ph.D., spoke on May 22 at the Research Triangle Park Headquarters as part of the RTI Modern Sciences Seminar Series. Rowland's talk, "Greenhouse Gases and Climate Change," was sponsored by the RTI Fellow Program and hosted by Senior Fellow R. K. M. Jayanty, Ph.D. Several NIEHS employees were among the audience gathered for the pre-lunch event.
Along with many other honors for his research, Rowland shared the 1995 Nobel Prize in Chemistry with Paul Crutzen, Ph.D., D.Sc., (http://www.mpch-mainz.mpg.de/~air/crutzen/) and Mario Molina, Ph.D., (http://www.geocities.com/shem_222hot/molina-autobio.html) for their transformative work in atmospheric chemistry. In its announcement(http://nobelprize.org/nobel_prizes/chemistry/laureates/1995/press.html) of the prize, the Royal Swedish Academy of Sciences praised the scientists for their "pioneering contributions to explaining how ozone is formed and decomposes through chemical processes in the atmosphere." Their work led to the banning of chlorofluorocarbons (CFC)-based aerosols in 1978.
Rowland began his talk with the events that inspired him to make his 1973 proposal to the U.S. Atomic Energy Commission for funding a predictive study of the atmospheric chemistry of CFC-11, as described in his 1995. "The starting for me in discussing the atmospheric changes that have been discovered in the second part of the 20th century," Rowland said at the beginning of his talk, "was the series of detailed measurements made [of carbon dioxide concentrations between 1958 and 1970]... at two places, Mauna Loa in Hawaii and the South Pole."
These findings set the stage for an accumulation of evidence by Rowland and other scientists that would lead to a landmark decision in 2007(http://www.nytimes.com/2007/04/03/washington/03scotus.html) written by Supreme Court Justice John Paul Stevens, reflecting the consensus of scientists about the reality of global warming. "The points [the majority decision made] included the well-documented evidence that the earth is warming, the well-documented evidence that there is a significant increase of carbon dioxide in the atmosphere, and the correlation that respected scientists have found between the two - namely that the carbon dioxide increase is mainly responsible for the temperature increase."
In the years between these two turning points in the discourse about the greenhouse effect, Rowland and his colleagues collected and evaluated some 50,000 air samples at sites throughout the world. The team analyzed concentrations of carbon dioxide and methane, which Rowland described as the "driving gases of greenhouse warming," as well as a number of other gases, including nitrous oxide and the CFCs, that are affected by human activity and, in their cumulative effects, also contribute to trapping heat in the atmosphere.
Rowland talked in some detail about methane, which has increased significantly due to the activities of humans over the past century from such sources as cattle, rice paddies and landfills. He also observed that the rate at which methane is entering the atmosphere had risen in recent decades. "During the 1980s, what one saw was that there was an increase of about one percent a year of the amount of methane in the atmosphere."
In addition to analyzing these measurements, according to Rowland, scientists have been able to corroborate the change in the atmosphere by examining trapped air bubbles in glacial core samples from such sites as the Quelccaya Glacier in Peru and the Vostok Glacier in Antarctica. "What you see as you go back in time," he continued, "is that carbon dioxide and methane levels peak at the same time as temperature."
Rowland cautioned his audience to avoid putting their faith in "a silver bullet" to stem the rate of global warming. "There may be a dozen things that can be seriously important in trying to control the climate changes that will happen, and it's worth exploring all of them."