Tuesday, September 11, 2007

Land use change and global warming

An interesting tidbit that showed up over at Nature's "Nature Reports: Climate Change" in a story on what might be the discovery of the missing carbon sink.

Albedo effect

Other scientists have also recently come to the conclusion that northern forests, although critically important in maintaining biodiversity, might be less important in slowing climate change than tropical forests. Govindasamy Bala and Ken Caldeira found that tropical forests help cool the Earth in two ways: by storing carbon and also by reflecting the suns warming rays back to space5. "Unlike tropical forests, high latitude forests darken the Earth's surface, causing the earth to absorb more sunlight, an effect that is most pronounced in snowy regions. This darkening of the surface has a warming influence that can be stronger than the cooling influence of carbon storage in these forests," says Caldeira. This suggests that removing high-latitude forests would have a net cooling effect on the planet, whereas removal of tropical forests would result in warming.

What is interesting here is what has been happening for the past 30 to 50 years. Northern forests have been growing and tropical forests have been shrinking. Thus, according to the above, this should lead to warming. How much of this land use change impact is included in the models of climate change? Not sure.

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