James Hansen
"James E. Hansen (born March 29, 1941 in Denison, Iowa) heads the NASA Goddard Institute for Space Studies in New York City, a part of the Goddard Space Flight Center in Greenbelt, Maryland, Earth Sciences Division. He is also currently an adjunct professor in the Department of Earth and Environmental Sciences at Columbia University. Hansen is best known for his research in the field of climatology and his testimony on climate change to congressional committees in the 1980s that helped raise broad awareness of the global warming issue. He is also noted for publishing 'an alternative scenario' for global warming which states that in the past few decades the warming effect produced by increased CO2 has been largely offset by the cooling effect of aerosols also produced in burning fossil fuels, and that most of the net warming so far is due to trace greenhouse gases other than CO2. He has been a critic of both the Clinton and current Bush Administration's stances on climate change."
Statements
"Recent analyses indicate that the amount of atmospheric CO2 required to cause dangerous climate change is at most 450 ppm, and likely less than that. Reductions of non-CO2 climate forcings can provide only moderate, albeit important, adjustments to the CO2 limit. Realization of how close the planet is to ‘tipping points’ with unacceptable consequences, especially ice sheet disintegration with sea level rise out of humanity’s control, has a bright side. It implies an imperative: we must find a way to keep the CO2 amount so low that it will also avert other detrimental effects that had begun to seem inevitable, e.g., ocean acidification, loss of most alpine glaciers and thus the water supply for millions of people, and shifting of climatic zones with consequent extermination of species."
-- Abstract of "How Can We Avert Dangerous Climate Change?" June 2007.
References
James Hansen's Website
How Can We Avert Dangerous Climate Change?
Wikipedia Entry: James Hansen