Tree-planting programs in the tropics work because tropical forests not only absorb carbon dioxide, a greenhouse gas, but also increase cloudiness, which helps cool the planet, said Govindasamy Bala of Lawrence Livermore National Laboratory in Livermore, Calif. Bala worked with scientists from University of Montpellier in France.

The team used computer models to predict what would happen to global temperatures in 2100 if forests were removed in 2000, NewScientist.com said Friday. Bala said this study differs from others because the models not only included trees' carbon-storing effects but also considered the trees' release of vapor and their foliage absorbing extra heat.

The climate warming because of leaves absorbing heat offsets the cooling effect from carbon uptake, Bala said. The team found that if they removed forests from the planet in 2000, global temperatures in 2100 were actually 0.2��C cooler than if forests remained.

"The value of our study is that it provides guidance on where the trees should be planted if the main purpose is to slow down global warming," Bala said.

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