Potsdam Institute research links record-breaking daily rainfall to global warming

Record-breaking daily rainfall, seen increasingly since 1980, is being linked to global warming caused by "human-induced greenhouse gases".

A team of scientists from Potsdam Institute for Climate Impact Research found that the worldwide increase in heavy daily rainfall is consistent with the rise in global temperatures.

During the 1980-2010 period, there was a more-than-expected 12% increase in such events, data collected from weather stations across the globe from 1901 to 2010 showed. South-east Asia alone recorded a 56% rise in such events.

"Due to the upward trend, the worldwide increase of record-breaking daily rainfall events in the very last year of the studied period reaches even 26 percent," lead author Jascha Lehmann said in a press release.

In 2010, Pakistan witnessed extreme rainfall, causing devastating floods followed by the deaths of hundreds of people from a cholera outbreak. In the same year, there were flash-floods in Texas caused by rainstorms.

Germany also witnessed three major flooding events in just a couple of years beginning 1997.

"In all of these places, the amount of rain pouring down in one day broke local records – and while each of these individual events has been caused by a number of different factors, we find a clear overall upward trend for these unprecedented hazards," says Lehmann.

In South-east Asian countries the increase in record-breaking rainfall events was as high as 56%. It was 31% in Europe and 24% in central US.

In contrast, the Mediterranean and Western US witnessed a 27% and 21% reduction, respectively. Both regions face the risk of severe drought.

Looking at the thermodynamics of the system, the scientists compared their findings to the Clausius-Clapeyron equation and found that the increase in unprecedented heavy rainfall events fits in with the expected increase under global warming.

"One out of ten record-breaking rainfall events observed globally in the past thirty years can only be explained if the long-term warming is taken into account," says co-author Dim Coumou. "For the last year studied, 2010, it is even one event out of four, as the trend is upward."

Before 1980, fluctuations in extreme rainfall events are explained by natural variability, while the post-1980 period bears the stamp of greenhouse gases.

"The pronounced recent increase in record-breaking rainfall events is, of course, worrying," says Coumou and adds, "Yet since it is consistent with human-caused global warming, it can also be curbed if greenhouse gas emissions from fossil fuels are substantially reduced."