Why is there a short-term increase in global precipitation in response to diminished CO2 forcing?
Article first published online: 24 MAR 2011
Copyright 2011 by the American Geophysical Union.
Geophysical Research Letters
Volume 38, Issue 6, March 2011
How to Cite
2011), Why is there a short-term increase in global precipitation in response to diminished CO2 forcing? Geophys. Res. Lett., 38, L06703, doi:10.1029/2011GL046713., , and (
- Issue published online: 24 MAR 2011
- Article first published online: 24 MAR 2011
- Manuscript Accepted: 28 FEB 2011
- Manuscript Revised: 21 FEB 2011
- Manuscript Received: 10 JAN 2011
- radiative forcing;
- fast and slow response;
- thermal inertia;
- ocean heat;
- hydrological cycle
 Recently, it was found that a reduction in atmospheric CO2 concentration leads to a temporary increase in global precipitation. We use the Hadley Center coupled atmosphere-ocean model, HadCM3L, to demonstrate that this precipitation increase is a consequence of precipitation sensitivity to changes in atmospheric CO2 concentrations through fast tropospheric adjustment processes. Slow ocean cooling explains the longer-term decrease in precipitation. Increased CO2 tends to suppress evaporation/precipitation whereas increased temperatures tend to increase evaporation/precipitation. When the enhanced CO2 forcing is removed, global precipitation increases temporarily, but this increase is not observed when a similar negative radiative forcing is applied as a reduction of solar intensity. Therefore, transient precipitation increase following a reduction in CO2-radiative forcing is a consequence of the specific character of CO2 forcing and is not a general feature associated with decreases in radiative forcing.