Upper-tropospheric moistening in response to anthropogenic warming

“Because water vapor is itself a very powerful greenhouse gas, the increase in water vapor further amplifies the initial CO2 induced warming. Our study confirms the presence of this key feedback mechanism which is a crucial component of global warming projections in water vapor can be explained by a rise in the amount of other greenhouse gases such as carbon dioxide being fed into the atmosphere.”

Co-author Brian Soden

• States that the fact water vapor is the most dominant greenhouse gas underscores the need for an accurate understanding of the changes in its distribution over space and time
• States that although satellite observations have revealed a moistening trend in the upper troposphere, it has been unclear whether the observed moistening is a facet of natural variability or a direct result of human activities
• Uses a set of coordinated model experiments to confirm that the satellite-observed increase in upper-tropospheric water vapor over the last three decades is primarily attributable to human activities
• States this attribution has significant implications for climate sciences because it corroborates the presence of the largest positive feedback in the climate system