A team from the Carnegie Global Ecology department have recently concluded that water evaporation on Earth actually cools down the atmosphere and fights global warming, but not in the way you’d be tempted to think.
You probably know from elementary classes that evaporation happens with energy consumption, thus taking the heat from the object and carrying it further. The most relevant example are those shivers you experience when you get out of the water – the evaporation causes you to lose heat – but you already knew that, didn’t you?
Well, some have argued that evaporation is actually bad for the environment, since the water vapors act as greenhouse gases, and that even if the heat is first extracted from the ground by evaporation, it then returns in the form of rain, respecting the second law of thermodynamics – energy cannot be neither created or destroyed.
The Carnegie researchers led by George Ban-Weiss concluded that the way water vapors fight against global warming is by forming low-altitude clouds, which reflect sunlight and heat back into space, thus preventing the further heating of the atmosphere.
A similar study performed last year, by Ken Caldeira, showed increased quantities of CO2 stop plants from sweating. Now, Caldeira, a member in Ban-Weiss’s team, reports:
“This shows us that the evaporation of water from trees and lakes in urban parks, like New York’s Central Park, not only help keep our cities cool, but also helps keep the whole planet cool. Our research also shows that we need to improve our understanding of how our daily activities can drive changes in both local and global climate. That steam coming out of your tea-kettle may be helping to cool the Earth, but that cooling influence will be overwhelmed if that water was boiled by burning gas or coal.”
Global warming may be caused by many things, including fossil fuel consumption, but as common sense suggests, taking down trees and entire forests ruins the Earth’s self-defense mechanism. Stopping the cutting of trees or accelerating the plantation of new vegetation could have has much or even bigger impact than making our cars more fuel efficient.