Earth sciences professor Eric Posmentier explained the complexities and uncertainties surrounding global climate change on Wednesday in his lecture entitled "A Climatologist's View of Climate Change -- Facts and Fallacies."
The speech was part of a series of lectures on climate change, and was co-sponsored by the Department of Earth Sciences and the Sierra Club, which supports the passage of legislation intended to slow climate change.
Postmentier stressed that definitive answers on global warming and climate change in general, are "intrinsically impossible to generate."
"The professor seemed a lot less confident in the occurrence of global warming than you usually hear about," James Preston '09 said. "I thought it was important that he brought up the uncertainty of the situation."
Despite these assertions, Postmentier offered evidence to support climate change. A doubling of carbon dioxide in the atmosphere since the beginning of the 20th century, for example, could potentially increase the Earth's temperature by 4.5 degrees Celsius.
Since 1860, the earth's average temperature has increased by 0.8 degrees Celsius. The cumulative amount of ice in the oceans has been continually decreasing since 1960.
Although data exists to support the hypothesis of global warming, Postmentier stressed that there are also facts to support the opposite view.
A phenomenon called an urban heat island, in which cities are considerably warmer than rural areas, could potentially distort data significantly. Some data show no warming whatsoever, and others even show a slight cooling in temperature over time.
Postmentier also addressed the inadequacy of the models currently used to forecast climate change. These models were originally intended to make short-term weather forecasts, but are now used to predict large-scale climate changes. Additionally, the models make some false assumptions that do not adversely affect short-term results but may significantly affect more distant climate predictions.
"Some of the assumptions being made with these models are just ridiculous for long-term forecasts," Postmentier said.
Some effects of global warming may either stabilize or destabilize other effects, complicating the prediction of climate change. Postmentier said that chance for abrupt climate change is also very possible, as there is a historical precedent of sudden, drastic fluctuations in temperature.
Although climate change is by no means clear, many people have taken an interest in the subject.
"Interest has been growing country-wide and worldwide, and apparently in Dartmouth," Sierra Club representative Denis Rydjeski said regarding the full lecture hall. "We're holding these lectures in response to public interest."
A second lecture of the series is scheduled for April 12, in which Jackie Ricter Menge will give a lecture entitled "A Polar Bear's View of Climate Change."
