Amplified Arctic precipitation increases are driven by atmospheric radiative cooling

As the climate warms, the amount of water vapour in the atmosphere increases by about 7 % per K, following the clausius-clapeyron relation. Globally averaged precipitation only increases by about 1-2 % per K of warming, as it is constrained by the atmospheric energy budget rather than the availability of moisture in the atmosphere. In the Tropics, zonally averaged precipitation mostly increases in the ITCZ near the equator and decreases in the subtropical dry zones (rich get richer, poor get poorer). A fundamental explanation of extratropical precipitation change has yet to be provided.

Here, we show that the structure of zonal mean mid-latitude precipitation changes is largely controlled by circulation changes, whereas amplified Arctic precipitation change is linked to increased atmospheric radiative cooling. The relative change in precipitation per unit of local warming is greater at high latitudes than anywhere else.