Tree vapours cool planet
Forests store carbon and help in this way to prevent global warming. But they do more: scientists in the UK and Germany have now discovered that trees release a chemical that thickens clouds above them, which then reflect more sunlight and cool the Earth more sufficiently.
The scientists looked at chemicals called terpenes that are released from boreal forests across northern regions such as Canada, Scandinavia, Russia and Siberia. But other trees also produce terpenes so the cooling effect should be found in other regions too, including the tropical rainforests.
The terpenes react in the air to form tiny particles called aerosols. The particles help turn water vapour in the atmosphere into clouds. The particles released by pine forests, for example, double the thickness of clouds some 1,000m above the forests, which causes them to reflect an extra 5% sunlight back into space. ‘It might not sound a lot, but that is quite a strong cooling effect. … It gives us another reason to preserve forests,’ says Dominick Spracklen of the Institute for Climate and Atmospheric Science at Leeds University.
The research suggests that the destruction of old-growth forests could accelerate global warming more than was thought, and that protecting existing trees could be one of the best ways to tackle the problem.
source: David Adam, Chemical released by trees can help cool planet, scientists find, The Guardian, 31 October 2008