Dec
02
2008

Water vapor in action: Hoh Lake, Washington.
Water vapor in action: Hoh Lake, Washington.Courtesy S. McAfee

I hate it when bad news gets confirmed.

That’s just what happened when Andrew Dessler and his colleagues at Texas A&M were able to show that a warmer atmosphere holds more water vapor. Unfortunately, water is a greenhouse gas, so more water vapor means the earth warms, so the atmosphere can hold more water, which is a greenhouse gas . . . I think you can see where this is going. It’s a nasty feedback circle. If the earth stays more or less the same temperature, we don’t worry about this too much because there’s a really good way to get water out of the atmosphere. In fact, it just shut down air and highway travel all over the East Coast.

It may seem like a no-brainer that warmer air holds more water, but these scientists were able to put solid numbers on the link between temperature and water vapor, which is a big deal. They used information from a satellite called the Atmospheric Infrared Sounder to measure the amount of water in the air.

Using information from 2003 to 2008, they found that for every 1 degree Celsius the earth warms, the extra water in the air traps 2 watts for every square meter of the earth. If you stored that up over a square meter for an hour, you could run a 100-watt light bulb for about a minute. Bet you wouldn’t even notice that in your electric bill. But the earth is big, so let’s put it in perspective and do the math.

The surface of the earth is 510,072,000 square kilometers. According to howstuffworks, your run-of-the-mill power plant puts out 3.5 billion kilowatts in a year. That means the extra warming that water vapor adds for every degree the earth gets warmer is about the same as the annual output of 290 power plants, give or take. That’s a lot of light bulbs.

Your Comments, Thoughts, Questions, Ideas

bryan kennedy's picture

Great post. I really like how you explained the science of this matter using the light bulbs.

The video from this research is interesting to watch. You can see how water vapor moves around the planet over time. It's a fascinating way to look at the deserts of the world. They are always noticeable on world maps because of their brown color and lack of vegetation. But watching the water vapor dance around their edges but never cover them is really illuminating.

posted on Tue, 12/16/2008 - 12:57pm

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