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Graph of the Week: Global Warming
J. Bradford DeLong
- We humans are now dumping a lot of carbon dioxide into the atmosphere--enough that if current trends continue the concentration of carbon dioxide in the atmosphere in 2100 will be twice what it is today.
- In the past an increase of 100 in the carbon dioxide concentration measured in parts-per-million-by-volume has been associated with an increase in temperatures of 9 degrees Celsius--16 degrees Fahrenheit.
- Will the higher carbon dioxide concentrations produce a warmer world? Almost surely.
- How much warmer will the world be in 2100? We don't know. It is very likely that some of the association between higher carbon dioxide levels and higher temperatures is the result of both being driven by some third factor--like solar radiation. So the world in 2100 will surely not be as much warmer--40 degrees Celsius, or 72 degrees Fahrenheit--as a naive reading of the history of the past 400,000 years would suggest.
- But it is unlikely that all of the association is due to both carbon dioxide levels and global temperatures being jointly driven by some third factor: higher carbon dioxide levels trap more heat inside the earth's atmosphere.
Professor of Economics J. Bradford DeLong, 601 Evans Hall, #3880
University of California at Berkeley
Berkeley, CA 94720-3880
(510) 643-4027 phone (510) 642-6615 fax
This document: http://www.j-bradford-delong.net/TotW/g3.html