Water evaporated from trees cools global climate

“Scientists have long debated about the impact on global climate of water evaporated from vegetation. New research from Carnegie’s Global Ecology department concludes that evaporated water helps cool the earth as a whole, not just the local area of evaporation, demonstrating that evaporation of water from trees and lakes could have a cooling effect on the entire atmosphere.” –from press release Carnegie Institution.

Evaporation uses heat energy to put water vapor into the atmosphere. Water vapor is a strong greenhouse gas. Furthermore, when that water vapor condenses into rain or snow, it gives up its heat back to the atmosphere. The evaporation-condensation cycle is, however, energy neutral. The difference, apparently is that the cycle produces clouds which reflect sunlight, less energy reaches the ground. According to the Carnegie research, the net effect is one of cooling. IPCC climate models do not do well with clouds and assume a positive feedback, whereas the Carnegie research shows a negative feedback. Note that the Carnegie research is also a computer simulation. With all computer modeling, results depend on assumptions. In view of the poor record  of the IPCC climate models versus observations, it seems that the Carnegie model is closer to reality.


This is why we need to take care of trees. Stop cutting them down and plant more trees!