Air pollution is believed to have increased river flow in the Northern Hemisphere, reveals a new study.

Air pollutants such as aerosols have been blamed in previous studies for preventing proper sunlight from reaching the Earth, an effect which is called "solar dimming." The lack of proper sunlight on the Earth's surface has led to reduced evaporation and an increased river flow.

Nicola Gedney from the British Met Office led the study, which reveals that it has detected solar dimming impacts on rivers in some of the industrial regions of Europe. Gedney indicates that river flow had increased by as much as 25 percent in central Europe when levels of aerosols were at their peak in the 1980s.

Scientists and environmentalists are in agreement that increased sulphurous coal burning until the 1970s led to extra ejection of aerosols into the Earth's atmosphere. However, solar dimming started to slow down and reverse in North America and Europe after efforts from government agencies, use of cleaner fuels and the introduction of clean air legislation.

Researchers observed that the solar dimming reversal resulted in the reduction of river flows. Diminishing river water level is also a cause of concern, which may affect estimations of future water supplies.

"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," says Gedney.

Chris Huntingford, co-author of the research, suggests that attribution and detection techniques used by the study were able to establish a connection between river flow changes and aerosols.

"These studies normally involve looking at how different factors affect temperature, but here we've been able to attribute this man-made influence to an environmental impact," says Huntingford.

The research also examined the impacts of carbon dioxide and deforestation on the increased level of river flow. The researchers believe that rising carbon dioxide levels may have also increased "river-flows by reducing water loss from plants."

Tim Cohn, a research hydrologist with the U.S. Geological Survey (USGS), suggests that the air pollution regulations in the U.S. have controlled the emissions of aerosols for many decades, which means that river flow increase in the country would have been lesser when compared with Europe.

Cohn also pointed out that the USGS regularly monitors river flows in the country to understand the link between climate change and human actions. The agency also measures the impact of this link to estimate the country's future water resources.

The study has been published in the journal Nature Geoscience.

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