水蒸气和温室效应有什么关系?

Andrew Dessler is an atmospheric scientist at Texas A&M University. He's an expert on water vapor, the most abundant greenhouse gas in Earth's atmosphere. At a science meeting in late 2009, Dessler told EarthSky that the effect water vapor plays in global warming is now understood.

Andrew Dessler:One of the durable urban legends you hear is that the models don't get water vapor right, or we don't understand water vapor. And that's no longer the case.

Dessler explained that water vapor has been proven to be a major contributor to global warming. He said carbon dioxide emissions provide the initial warming, by increasing surface temperatures on the planet. Warmer temperatures cause more water to be evaporated off the oceans, which increases the amount of water vapor, or humidity, in the air.

Andrew Dessler:The higher humidity in the atmosphere, because water vapor is a greenhouse gas that gives you additional warming. It's that amplification that we call the ‘water vapor feedback.’

Dessler said data from AIRS, a NASA satellite instrument that measures water vapor across the world, confirmed this feedback.

Andrew Dessler:You get about twice the warming with the water vapor feedback than you would without the water vapor feedback.

In other words, water vapor makes carbon dioxide twice as effective at warming the planet.

I'm Deborah Byrd. EarthSky is a clear voice for science. We’re at www.hxen.net