Atmospheric Sciences & Global Change Division
Better understanding of the sensitivity of the earth's climate system to changes in greenhouse gases critically important
AS&GCD's Ruby Leung's research and recent work by Jae Edmonds at the Joint Global Change Research Institute demonstrate the critical importance of better understanding the sensitivity of the Earth's climate system to changes in greenhouse gases. In an invited presentation at the Workshop on Greenhouse Gas Stabilization Scenarios held January 21-22, 2004 at the National Institutes for Environmental Studies in Tsukuba Japan, Edmonds explored the interplay between the physics of the climate system and policies that would need to be enacted to deal with the negative impacts of climate change. One of Edmond's principal observations is the importance of climate sensitivity, i.e., the change in global mean surface temperature to a doubling of CO2 concentrations, in determining the concentration at which future CO2 concentrations must be stabilized. If increases in global-average surface temperatures must be limited to no more than 2C in order to avoid unacceptable damage to the environment, a climate sensitivity to CO2 doubling of 1.5C means that the concentration of CO2 could safely rise above 700 ppm, while a climate sensitivity of 4.5C means that the CO2 concentration would have to be stabilized at 400 ppm. Both of these climate sensitivity values are within the current range of uncertainty.
Edmonds' study also emphasized the economic consequences of better understanding of climate sensitivity. If climate sensitivity is on the low end of the current uncertainty range the cost of achieving stabilization of CO2 concentrations will be trillions of dollars cheaper that if it is on the high end of this range.