There are a whole lot of reasons to be a fan of trees. They provide shade, you can hang swings off of them, and they look cool in autumn. We also know trees play an important part in regulating our climate. They participate in the process of terrestrial carbon sequestration -- absorbing carbon dioxide and storing it in biomass, rather than letting it get into the atmosphere, where it can contribute to global warming.
But now we find that trees help fight climate change in another way. Researchers from Carnegie's Global Ecology department found that evaporation of water from trees not only cools things locally, but also globally, as well.
While evaporation releases water vapor (a strong greenhouse gas), the cycle that the good folks at Carnegie have identified produces clouds that reflect sunlight, meaning less energy (heat) makes landfall. The net result? Cooling.