Trees take CO2 out of the air - true. But when they die and rot, or are burned, they eventually recycle their carbon back into the atmosphere. It's the [link|http://earthobservatory.nasa.gov/Library/CarbonCycle/|carbon cycle]. It only takes a few days to a few thousand years for the carbon from trees to move back into the air.

The major problem is, we're taking a lot of carbon that was locked up in the Earth over millions of years and dumping it in the air over a few decades. It'll take a long time for that carbon to reach equilibrium with the carbon cycle, and in the meantime it looks like it's causing the Earth's atmosphere to warm.

If this picture is correct, then burning trees and ethanol isn't as big a disruption of the carbon cycle as burning coal, natural gas, and oil. But of course our modern economy would collapse if we had to give up petroleum. "Give me half-a-cord of oak for the Steamer, Mac." It also means that planting more trees won't solve the global warming problem because it'll take millions of years for the trees to lock up the carbon in stores that are away from the near-surface carbon cycle. (Unless we want to bury the wood in coal mines or the like.)

But [link|http://www.economist.com/science/displaystory.cfm?story_id=8998216|trees do much more than (temporarily) lock up carbon].

HTH!

Cheers,
Scott.

Some other models are that the last ice age ended due to [link|http://news.nationalgeographic.com/news/2003/03/0317_030317_iceshelf.html|collapse of an Antarctic ice shelf], or [link|http://www.bbc.co.uk/weather/features/understanding/iceage_01.shtml|movement of the continents changing ocean currents], or [link|http://media.www.dailyemerald.com/media/storage/paper859/news/2007/11/28/News/The-End.Of.An.ice.Age-3119506.shtml?refsource=collegeheadlines|a comet hitting Canada], [link|http://www.dailybruin.ucla.edu/news/2006/oct/20/bogs-may-have-helped-global-wa/|bogs], etc.

:-)

I don't know enough about bogs and so forth, but it certainly seems to be the case that [link|http://news.nationalgeographic.com/news/2004/12/1201_041201_siberian_bogs.html|bogs can release tremendous amounts of CO2 and methane] as they warm. It looks like the [link|http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16905|Earth's albedo] is a major factor, one that trees and bogs will impact.

Thanks.

Cheers,
Scott.