Rising aerosol levels around 1980, by the dimming of incoming solar radiation, led to a substantial increase in river runoff from some northern hemisphere rivers, suggests a study published online in Nature Geoscience. If this link between aerosols and river flow holds in the future, runoff may decline as air quality improves in response to legislation.

Using a detailed land-surface model together with an estimate of surface meteorology for the twentieth century, Nicola Gedney and colleagues simulated the response of river runoff to climate fluctuations. They detected a statistically significant response of river flow to aerosols both over the northern hemisphere as a whole and in individual river basins. In the Oder basin, one of Europe’s most heavily polluted, the increase in annual runoff amounted to up to 25% compared with the long-term mean.