Solar dimming increases river flow

Air pollution significantly impacts the amount of water flowing through rivers in the northern hemisphere, a new study has shown. Results showed that water flow increased by up to 25 per cent.

The study published in Nature Geoscience shows how solar dimming caused by air pollution known as aerosols increases river flows relative to that expected from surface meteorology.

According to the study, the reduced amount of sunlight affected the rate of evaporation from the Earth’s surface. When the dimming began to reverse, reductions in river flows were observed, found the researchers from the Met Office, Centre for Ecology and Hydrology, University of Reading, Laboratoire de Météorologie Dynamique in France and the University of Exeter.

Nicola Gedney of the Met Office, lead author of the paper, said: “We detected the impact of solar dimming on enhanced river flows over regions in the heavily industrialised northern extra-tropics. We estimate that, in the most polluted central Europe river basin, this effect led to an increase in river flow of up to 25 per cent when the aerosol levels were at their peak, around 1980.

“With water shortages likely to be one of the biggest impacts of climate change in the future, these findings are important in making projections for the future.”

It is already established that increased burning of sulphurous coal up to the late 1970s led to additional aerosols in the atmosphere. These are reflective and therefore reduce the amount of sunlight reaching the Earth’s surface, an effect known as ‘solar dimming’.

This dimming then started to reverse in Europe and North America with the introduction of clean air legislation and a widespread switch to cleaner fuels.

The study also tested for the effects of deforestation and carbon dioxide increases on river flow.

Photo credit: Richard Petry/ CC BY-NC-ND 2.0

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