Have aerosols affected precipitation variations in Europe

According to cloud physics, an increase in sulphate aerosol concentrations may reduce cloud droplet sizes and thus inhibit precipitation, while decreasing aerosol concentrations may have the opposite effect. Here, we investigate whether the large variations in anthropogenic sulphate emissions over the last decades have had a notable effect on precipitation in Europe. We use point observations as well as gridded data sets of precipitation to study changes in the heavily industrialized region on the borders of Poland, the Czech Republic and Germany, formerly known as the “Black Triangle” (BT). High concentrations of sulphuric gases in this area caused severe forest dieback in the 1970s and -80s, after which the air quality has improved significantly. Changes in the BT area are compared to changes in a clean region at the western coast of Europe, where trends in pollution have been minor.