Predictions that our warming world will become a wetter place have been confirmed by a study which suggests that extreme rainstorms will rise by more than 10 per cent by the year 2050.
For some time, computer models of the global climate have predicted that global warming will increase the intensity of rainfall and it is these extremes, linked with landslides and flooding, that are among the major impacts.
Woman walking in heavy rain: extreme rainstorms will increase by 10 per cent by the year 2050
Today, in the journal Science, a study conducted at the University of Reading and the University of Miami provides the first hard evidence to confirm the link between a warmer climate and more powerful rainstorms, suggesting that extreme events may be even more common than predicted.
To understand how rainfall responds to a warmer climate, the researchers used a natural long term climate pattern called El Niño, a warming originating in the Pacific off South America that influences weather patterns around the globe.
Based on nearly 20 years of satellite observations the team could examine the relationship between tropical rainfall and changes in surface temperature as well as in atmospheric moisture.
In this way, they found a distinct link between tropical rainfall extremes and temperature, with heavy rain events increasing during warm periods and decreasing during cold periods.
"A warmer atmosphere contains larger amounts of moisture which boosts the intensity of heavy downpours," said Dr Brian Soden, at the University of Miami.
Changes in heavy rainfall seem to keep pace with atmospheric moisture which rises by around 7 per cent for each ºC of warming. Based on computer models, this could mean an increase in the intensity of heavy rainfall of around 10 per cent by 2050.
However, the observed increase in extreme downpours appears to be larger than the increases predicted by current computer simulations, suggesting that predicted changes in rainfall due to global warming may be underestimated, either because of flawed measurements or because computer models lack some key understanding, for instance of the action of aerosol particles in the atmosphere.
The researchers say it is difficult to be precise about the underestimate and add that it is crucial to determine the cause for this discrepancy as soon as possible in order to accurately understand the implications of global warming and its effects on the water cycle.
"Comparing observations with results from computer models improves understanding of how rainfall responds to a warming world" said Dr Richard Allan, NERC advanced fellow at the University of Reading's Environmental Systems Science Centre. "Differences can relate to deficiencies in the measurements, or the models used to predict future climatic change.
"Heavy rain in the tropics is often associated with thunderstorms and the same processes will also apply in the UK, particularly in summer where intense downpours are fueled by the additional moisture carried by warm, humid air.
"One of the most serious challenges that humanity will face in response to climate change is adapting to changes inextreme weather events. There is a major concern that heavy rainstorms will become more common and more intense in a warmer climate.
"Floods can completely devastate areas and people's livelihoods and so this knowledge could have massive implications on how we plan for our changing climate in the future."