Wednesday, April 25, 2007

One Tree Short of a Forest

Carbon credits are the modern day equivalent of the Medieval Papal Indulgences. It goes like this; to compensate for all the carbon that your evil daily activities produce (like wiping your arse), companies are springing up offering to plant trees in exchange (trees absorb CO2 by photosynthesis, you see). Sounds neat, eh?

Tree Appeal 'helps responsible organisations reduce their environmental footprint by planting native British trees'.
It's even got the seal of approval of His Toniness.

Carbon Neutral, an Australian company goes one step further. They will calculate your annual CO2 consumption and then translate that into the number of trees needed to be planted per annum (at the very reasonable price of $3 per tree).

However, Govindasamy Bala a physicist specialising in climate change at the University of California has put the proverbial spanner in the works of this latest gimmick.

Dr. Bala, has found, rather inconveniently, that removing all of the world's trees might actually cool the planet down.

There are two counteracting forces at work;
i) Forests absorb more of the sun's heat than vegetation which might otherwise occupy the same stretch of land. That warms things up.

ii) Transpiration (the process by which trees absorb water from the ground and evaporate it into the atmossphere) tends to make things cloudier, and those clouds, in turn, reflect the sun's heat back into space cooling things down.

Under Dr. Bala's model, if all the planet's trees are cleared, the levels of CO2 in the atmosphere actually doubles but paradoxically the planet's temperature cools. This is because although deforestation would cause an additional 1.3C temperature rise because of the increased CO2, the additional reflectivity of the planet would cause 1.6C of cooling - a net cooling of 0.3C.

Still, tree planting does sound a nice idea, doesn't it. And if it helps you sleep at night then who cares if the science behind it is a crock.
Update; i wonder of this line of argument will work with my employer!