In a study published in the journal Climatic Change, researchers from the Potsdam Institute for Climate Impact Research found that the rise in the number of extreme rainfall events is consistent with an increase in global temperatures.

The researchers gave Pakistan and Texas in 2010 as examples of extreme rainfall events that brought record-breaking levels of precipitation, as well as Germany where once-in-a-century flooding events have been experienced just years apart starting in 1997. Lead author Jascha Lehmann said that different factors brought about the rainfall events but an overall upward trend was still clear based on the results of their study.

The researchers examined rainfall data gathered between 1901 and 2010 using advanced statistical analysis. According to data from thousands of weather stations around the world, there was a 12 percent increase in the number of extreme rainfall events than what could be expected if global warming was not in the picture.

These extreme rainfall events followed distinct patterns all over the world but wet regions generally saw the increase in extreme rainfall compared to drier parts of the globe. In Southeast Asia, record-breaking rainfall events increased by up to 56 percent, 31 percent in Europe and 24 percent in central U.S.

A statistical analysis was not able to offer direct relations that could indicate why it rained more as temperatures rose but the researchers believe that the Clausius-Clapeyron equation is in effect. With warmer air holding more water, the additional moisture retained when the weather is hot translates to heavy rainfall in short-term events.

"One out of 10 record-breaking rainfall events observed globally in the past 30 years can only be explained if the long-term warning is taken into account," said Dim Coumou, a co-author for the study.

Previous studies have not been able to fully confidently associate greenhouse gases with increase in rainfall events on a regional and global scale but this new study offers the first set of observational data to view rainfall events within the context of global warming.

The researchers admit that the increase in record-breaking rainfall events is worrying but given its association with global warming, the results of the study also hint at the possibility that curbing greenhouse gas emissions (major contributors to man-made global warming) can take care of the problem.

Katja Frieler also contributed to the study.

Photo: Christian Kadluba | Flickr

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