Washington: The frequency of downpours of heavy rain — which can lead to flash floods, devastation, and outbreaks of waterborne disease — has increased across the globe in the past 50 years due to climate change, a study has found.
According to the research published in the journal Water Resources Research, number of extreme downpours increased steadily between 1964 and 2013 — a period when global warming also intensified.
The study screened data from over 8,700 daily rain records from the 100,000 stations monitoring rain worldwide for quality and consistency.
“By introducing a new approach to analysing extremes, using thousands of rain records, we reveal a clear increase in the frequency extreme rain events over the recent 50 years when global warming accelerated,” said Simon Papalexiou, a hydro-climatologist at the University of Saskatchewan in Canada.
Various parts of Canada, most of Europe, the Midwest and northeast region of the US, northern Australia, western Russia and parts of China have faced this rapid increased frequency of ‘extreme precipitation events’.
“This upward trend is highly unlikely to be explained by natural climatic variability. The probability of this happening is less than 0.3 per cent under the model assumptions used,” said Papalexiou, who led the research.
Between 2004 and 2013, there were seven per cent more extreme bouts of heavy rain overall than expected globally. In Europe and Asia, there were 8.6 per cent more ‘extreme rain events’ overall, during this decade.
Global warming can lead to increased precipitation because more heat in the atmosphere leads to more atmospheric water which, in turn, leads to rain.
Torrents of rain not only lead to flooding, but can threaten public health, overwhelming sewage treatment plants and increasing microbial contaminants of water.
More than half a million deaths were caused by rain-induced floods between 1980 and 2009.Heavy rain can also cause landslides, damage crops, collapse buildings and bridges, wreck homes, and lead to chaos on roads and to transport, with huge financial losses.
“Our results are in line with the assumption that the atmosphere retains more water under global warming,” said Alberto Montanari, a professor at the University of Bologna.
“The fact that the frequency, rather the magnitude, of extreme precipitation is significantly increasing has relevant implications for climate adaptation. Human systems need to increase their capability to react to frequent shocks,” Montanari added.
Regions in South America and Africa were excluded from the study, as records for the study period were not complete or robust.
According to Papalexiou, planning for more frequent ‘extreme’ rain should be a priority for governments, local authorities and emergency services.
“If global warming progresses as climate model projections predict, we must have better plan strategies for dealing with frequent heavy rain right now, especially when potentially devastating bouts of extreme rain are increasing decade by decade, “ said Papalexiou.
“We know that rainfall-induced floods can devastate communities, and that there are implications of increasing bouts of heavy rain for public health, agriculture, farmers’ livelihoods, the fishing industry and insurance, to name but a few,” he added.