Summer rainfall patterns in the Southern Hemisphere have changed markedly in response to rising greenhouse-gas concentrations and ozone-layer depletion, both caused by human activity.

Since the 1960s, southern regions at mid-latitudes have become drier whereas a zone around Antarctica has grown wetter. John Fyfe at the Canadian Centre for Climate Modelling and Analysis in Victoria, British Columbia, and his colleagues found that the observed trends agree with predicted precipitation patterns obtained from a set of 29 climate models.

They found that greenhouse gases and ozone changes were primarily responsible for the shifts in precipitation levels. Moreover, natural climate variability cannot explain the observed and modelled trends, the team found.

Geophys. Res. Lett. http://dx.doi.org/10.1029/2012GL054199 (2012)