Most climate scientists agree that the Earth's climate is getting warmer, but models predicting the severity of the temperature rise span a (relatively) broad range. One big reason for this is the difficulty in modeling things like cloud cover and how different air masses mix and move around each other. "Specifically, they have differences in how water-rich air at the bottom of the atmosphere gets mixed with the layers immediately above it. In some cases, this mixing increases rapidly as the temperature rises, effectively drying out the lower atmosphere and suppressing cloud formation there. This in turn would enhance the warming effect. In others, the increase in mixing is more gradual, limiting the impact of warming on clouds. The former produces a higher climate sensitivity; the latter a lower one. ... So, the authors turned to the atmosphere, using data to determine the relative importance of these processes (abstract). In the end, they find that the models that dry out the lower atmosphere more quickly are likely to get the process right. And, in these models, the mixing increases the drying rate in the lower atmosphere by about five to seven percent for each Kelvin the Earth's temperature increases. In contrast, the rate of evaporation, which adds moisture to the lower atmosphere, only increases by two percent for each Kelvin. Thus, the lower atmosphere dries out, cloud formation there is suppressed, and the planet warms even further. How much more will it warm? Quite a bit."
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