Global warming leads to more rain – but little of the change occurs over land. An international team of researchers, led by Bjørn H. Samset at the Norwegian CICERO Center for Climate Research, used ten global climate models to study how precipitation changes when just one factor in the climate system was allowed to change at a time.
While models tend to give very different predictions of future rainfall for realistic scenarios, changes due solely to greenhouse gases, aerosols, or the amount of incoming sunlight, give clearer results. Overall, the amount of rain over oceans increases by 4% per degree Celsius, no matter what caused the surface warming. Over land, the increase is only 1-2%. This difference helps explain why observed rainfall changes over land have so far been modest.
- Weak hydrological sensitivity to temperature change over land, independent of climate forcing
B. H. Samset, G. Myhre, P. M. Forster, Ø. Hodnebrog, T. Andrews, O. Boucher, G. Faluvegi, D. Fläschner, M. Kasoar, V. Kharin, A. Kirkevåg, J.-F. Lamarque, D. Olivié, T. B. Richardson, D. Shindell, T. Takemura & A. Voulgarakis