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Does the color of water effect the evaporation rate, and if so how does it effect the world?
- Simon (age 14)
Battle Creek Middle School, St. Paul, MN, U.S.A.
We get a lot of canned questions about water color and evaporation, but
yours has a useful twist. Obviously darker-colored water absorbs more
light if it's exposed to sunlight and thus heats up more and evaporates
faster. The biggest important difference is between liquid water in the
oceans and frozen water, which reflects much more energy. As global
warming sets in from our reckless emissions of CO2 and other greenhouse
gases, there is less ice and more water, so more sunlight gets
absorbed. Therefore more water evaporates. Water vapor itself is a
greenhouse gas, so that amplifies the effect further. It's hard to
calculate exactly how big this effect is, because it requires modeling
how heat distributes in the oceans. That's one of the biggest
uncertainties in estimates of how bad global warming will get. A
combination of several positive feedback effects of this sort might
lead to truly disastrous consequences, but right now the probability of
more or less serious outcomes is hard to calculate.
(republished on 07/24/06)
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