Climate Sensitivity and Feedbacks

Elizabeth R. Purdy

CLIMATE SENSITIVITY IS generally defined as the global mean surface temperature change that is followed by the doubling of carbon dioxide (CO 2 ) in the atmosphere. Put simply, climate sensitivity is the amount that temperatures rise or fall in response to alterations in climate. Since 1990, official estimates of climate sensitivity have ranged between 2.7–8.1 degrees F (1.5–4.5 degrees C). In the summer of 2004, at the Workshop on Climate Sensitivity, researchers generally agreed that temperatures have warmed by 0.6 degrees C over the last 100 years. Feedbacks are mechanisms that amplify or diminish climate change. Examples include water vapor, land ice-cover, vegetation cover, and ocean heat transport. Feedbacks may be affected by physical processes such as wind, snow, and seasonal variations. Climatologists have identified three major ways in which climate sensitivity and feedbacks may be studied using computer models. The first method uses a three-dimensional global climate model ...

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