Muons penetrate much further than X-rays, they do essentially zero damage, and they are provided for free by the cosmos.
Image credit: Science Source/Digital Globe.
Edited by Susan Solomon, Massachusetts Institute of Technology, Cambridge, MA, and approved September 9, 2013 (received for review May 30, 2013)
Significance
We show observational evidence for a stratospheric water vapor feedback—a warmer climate increases stratospheric water vapor, and because stratospheric water vapor is itself a greenhouse gas, this leads to further warming. An estimate of its magnitude from a climate model yields a value of +0.3 W/(m2⋅K), suggesting that this feedback plays an important role in our climate system.
Abstract
We show here that stratospheric water vapor variations play an important role in the evolution of our climate. This comes from analysis of observations showing that stratospheric water vapor increases with tropospheric temperature, implying the existence of a stratospheric water vapor feedback. We estimate the strength of this feedback in a chemistry–climate model to be +0.3 W/(m2⋅K), which would be a significant contributor to the overall climate sensitivity. One-third of this feedback comes from increases in water vapor entering the stratosphere through the tropical tropopause layer, with the rest coming from increases in water vapor entering through the extratropical tropopause.
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: adessler{at}tamu.edu.
Author contributions: A.E.D. and M.R.S. designed research; A.E.D. and T.W. performed research; A.E.D., T.W., S.M.D., and K.H.R. analyzed data; and A.E.D. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Stratospheric water vapor feedback
Article Classifications
- Physical Sciences
- Earth, Atmospheric, and Planetary Sciences
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