Scientists at Lawrence Livermore National Laboratory in California report that changes in precipitation over the world's land and oceans can not be explained by natural variability alone and are directly affected by human activities.
In a new study, Kate Marvel and Celine Bonfils compared climate model predictions with weather data observed over more than three decades. They note that higher global temperatures increase humidity, which makes wet areas wetter and dry ones dryer. And, increased greenhouse gases and ozone depletion affect atmospheric circulation patterns, pushing storms toward the poles.
Writing in the Proceedings of the National Academy of Sciences
, they say while natural fluctuations in climate can lead to either intensification or poleward shifts in rain and snow, it is very rare for the two effects to occur together naturally. Kate Marvel concludes, "External influences such as the increase in greenhouse gases are responsible for the changes."