AMERICAN GEOPHYSICAL UNION

2006 Fall Meeting

Will afforestestion strategies help mitigate global warming?

AU: Caldeira, K

EM: kcaldeira@globalecology.stanford.edu

AF: Carnegie Institution, 260 Panama Street, Stanford, CA 94305 United States

AU: Wickett, M

EM: wickett1@llnl.gov

AF: Lawrence Livermore National Laboratory, L-103 Energy and

Environment Directorate 7000 East Avenue, Livermore, CA 94550 United

States

AU: Phillips, T

EM: phillips14@llnl.gov

AF: Lawrence Livermore National Laboratory, L-103 Energy and

Environment Directorate 7000 East Avenue, Livermore, CA 94550 United

States

AU: Lobell, D

EM: lobell2@llnl.gov

AF: Lawrence Livermore National Laboratory, L-103 Energy and

Environment Directorate 7000 East Avenue, Livermore, CA 94550 United

States

ABSTRACT: The prevention of deforestation and promotion of

afforestation have often been cited as strategies to slow down and

mitigate global warming. Deforestation releases CO2 to the

atmosphere, which exerts a warming influence on Earth's climate.

However, biophysical effects of deforestation, which include changes

in land surface albedo, and evapotranspiration with associated

changes in the cloud cover, also affect climate. While changes in

albedo are expected to cool the surface and the evapotranspiration

changes could result in warming. What are the combined carbon cycle

and climate effects of deforestation? Here we present simulations

from a three- dimensional coupled global carbon-cycle and climate

model indicating that, on a global-mean basis, deforestation has a

net cooling influence on Earth's climate. The warming carbon-cycle

effects of deforestation are more than offset by the net biophysical

cooling. Our results imply that attempts to slow global warming by

promoting afforestation are likely to be counter- productive in

Northern mid- and high-latitudes, and ineffective elsewhere. We

stress, however, that forests are environmentally valuable resources

even if they exert a net warming influence on the global climate

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