Water vapor in the upper atmosphere amplifies global warming, says new study

A new study shows that water vapor high in the sky and the temperature at the Earth’s surface are linked in a “feedback loop” that further warms our climate.

According to the study this feedback loop could be about 10% of the climate warming from all greenhouse gases.

For well over 100 years it has been known that increased emissions of greenhouse gases such as carbon dioxide will warm the planet. As the lowest layer of the atmosphere, called the troposphere is warmed, the air becomes more humid because warmer air holds more water vapor. This “tropospheric water vapor feedback” approximately doubles the initial warming caused by carbon dioxide.

The new study shows that in addition to the well-understood tropospheric water vapor feedback on climate change, there is also a significant amplifying feedback associated with water vapor in the stratosphere, the layer of the atmosphere above the troposphere that extends to ~30 miles above Earth’s surface.

The new results suggest that the stratospheric water vapor feedback may be an important component of our climate system. The researchers estimated that at a minimum this feedback adds another ~5-10% to the climate warming from the addition of greenhouse gases, and is possibly substantially more than this amount.

http://research.noaa.gov/News/NewsArchive/LatestNews/TabId/684/ArtMID/1768/ArticleID/10307/Water-vapor-in-the-upper-atmosphere-amplifies-global-warming-says-new-study.aspx