AGU: Geophysical Research Letters

 

Editors' Highlight

Water vapor climate feedback inferred from the past 5 years of climate fluctuations

Warming temperatures evaporate water, increasing humidity. This increase in humidity has the potential to further warm the atmosphere because water vapor is a potent greenhouse gas. This water vapor feedback has the capacity to about double the direct warming from greenhouse gas increases. Using satellite data, Dessler et al. (2008) observed and quantified the behavior of atmospheric water vapor and the water vapor feedback during variations of the Earth's climate between 2003 and 2008. They found that global averaged surface air temperatures on Earth varied by 0.6°C during the years analyzed, with specific humidity over most of the troposphere increasing with rising global surface temperature averages. Relative humidity increased in some regions and decreased in others, with the global average remaining nearly constant at most altitudes. The water vapor feedback implied by these observations is strongly positive, similar to that seen by climate models. The magnitude of the feedback is similar to that obtained if the atmosphere maintained constant relative humidity everywhere.

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