Environment
Sheila Sund/Flikr
Aerosols — like the carcinogenic, black smoke from coal stacks — prevent sunlight from hitting the Earth, reducing evaporation and swelling the world's rivers. But as clean air legislation and a transition toward renewable energy reduce these contaminants, evaporation will increase, sucking away valuable freshwater — especially in Europe, according to a report published Sunday in the journal Nature Geoscience.
“We estimate that, in the most polluted central Europe river basin, [air pollution] led to an increase in river flow of up to 25 percent when the aerosol levels were at their peak, around 1980,” Nicola Gedney, lead author of the study, said in a press release.
The study was a collaborative effort of the Met Office, Britain’s national weather service; Britain’s Centre for Ecology and Hydrology; the University of Reading; Le Laboratoire de Météorologie Dynamique in France; and the University of Exeter.
Aerosols were pumped into Earth’s atmosphere starting with the industrial revolution in the early 20th century, peaking in 1980. These contaminants, pieces of particulate matter as opposed to gases like CO2, blocked sunlight, which in turn reduced the rate of evaporation from rivers in North America and Europe causing the bodies of water to swell.
In recent decades, the United States and European countries began to introduce clean air legislation and transition away from dirty fossil fuels to green energy alternatives in an attempt to combat climate change. This, as expected, decreased the amount of aerosols present in the atmosphere.
But with less sunlight blocked by the aerosols, evaporation rates have increased, leading to a reduction in river flow.
Diminished levels of river water could have a major impact on future water supplies, researchers warn.
“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,” Gedney said.
Tim Cohn, a U.S. Geological Survey (USGS) research hydrologist, told Al Jazeera that the study helps to confirm previous findings that pointed to the same reduction in river flow.
While trends in U.S. rivers are consistent with the report, Cohn said, the U.S. emitted significantly fewer aerosols than Europe over the past several decades — largely due to the Clean Air Act and other air pollution regulations. Because of that, the effect of reduced river flow in the U.S. will not be as pronounced as in Europe where aerosol reduction will be more dramatic.
Cohn said the USGS monitors all stream flow to gain an understanding of how human activity and climate change is occurring and what impact it has on water resources for the nation.
"A lot of this work, like this paper, depends on the existence of long-term data collection efforts — which are expensive and hard to keep funded," Cohn said. "We wouldn't know the models worked without data to compare it to."
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