Evaporated water from trees cool climate

Researchers from Carnegie's Global Ecology department have announced new research suggesting that evaporated water from trees play a key role in cooling the climate globally. This could have profound implications for policy makers looking at land-use change.

The urban heat island effect is one consequence of removing trees and vegetation from an area. As they are removed, there is less evaporative cooling taking place, increasing the local temperature. This is compounded with the albedo effect of the dark absorbent asphalt and concrete. Now researchers are saying that this evaporative effect has an impact on global, not just local climate as seen in cities.

Up until now, scientists were not sure whether water vapour had a net cooling or warming effect on the climate. It is everywhere, and as such very difficult to monitor in the environment. As a greenhouse gas, water vapour could have a net warming effect, but this research suggests otherwise. Intitially one would think that evaporation would cause no net influence on climate, as any energy lost in the evaporative process would be returned to Earth as it is a closed system.

This research however, shows that the cloud forming effect of water vapour causes a change in the albedo of the atmosphere, reflecting more energy from the sun back into space.

More studies are required to understand just how much this water vapour evaporation effect has on climate, but we can be sure it now has a net cooling effect.