Thank you global warming: Manmade CO2 emissions saved rain from manmade air pollution, study claims

Claim: Manmade aerosols reduced the hydrological cycle during the 1950s-1980s, then global warming brought it back.

The study abstract (from Nature Climate Change) is below.


Anthropogenic impact on Earth’s hydrological cycle

Peili Wu*, Nikolaos Christidis and Peter Stott

The global hydrological cycle is a key component of Earth’s climate system. A significant amount of the energy the Earth receives from the Sun is redistributed around the world by the hydrological cycle in the form of latent heat flux1. Changes in the hydrological cycle have a direct impact on droughts, floods, water resources and ecosystem services. Observed land precipitation2–4 and global river discharges5 do not show an increasing trend as might be expected in a warming world6–11. Here we show that this apparent discrepancy can be resolved when the effects of tropospheric aerosols are considered. Analysing state-of-the-art climate model simulations, we find for the first time that there was a detectable weakening of the hydrological cycle between the 1950s and the 1980s, attributable to increased anthropogenic aerosols, after which the hydrological cycle recovered as a result of increasing greenhouse gas concentrations. The net result of these two counter-acting effects is an insignificant trend in the global hydrological cycle, but the individual influence of each is substantial. Reductions in air pollution have already shown an intensification in the past two decades12–14 and a further rapid increase in precipitation could be expected if the current trend continues.