The cloudy, warming Earth

Bad Astronomy
The entire universe in blog form
June 11 2010 7:07 AM

The cloudy, warming Earth

NASA just released an interesting picture of our home planet, taken from the GOES satellite:

goes_earth_20100530

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

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This image is in the infrared, and maps out the heat emitted from Earth. Brighter spots are giving off more IR -- like the desert region in southwest South America, and the westernmost tip of Africa peaking over on the right -- and darker spots show areas where less IR is emitted.

You might think that these dark spots are cooler, but you have to be careful here. The dark areas are actually cool high clouds. But they also trap the heat of the Earth -- they don't heat up themselves, but prevent the heat below them from escaping. High clouds like this are in reality warming us up slightly, even though they themselves are cold!

Interestingly, the low clouds in the image are white, as is open ocean. That means that the Earth is good at radiating away heat from its surface whether or not low clouds are present. Low clouds let the heat right through! So the type of cloud present affects the way the Earth's temperature is maintained.

One lesson to be learned here -- and it's a good one -- is that figuring out how the planet heats up and cools off is very complicated. A corollary of this is that when someone (a politician, say, or a demagogue) starts railing about scientists who are struggling with this information, they are almost certainly oversimplifying the case. Yeah, this stuff is hard. But that's precisely why I tend to side with the majority of scientists who devote their lives to looking at this data, and not some talking head on TV whose only job is to confuse the issue even further.

[Note: I'll have another post on this very topic coming very soon. Stay Tuned.]

Image credit: Rob Simmon, GOES Project Science Office, NASA



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