A Warming Earth Will Bring More Extreme Rainfall, New Research Shows – Forbes
Some two thirds of the world’s land area will experience wetter, more variable conditions as the Earth warms, making extreme rainfall and flooding more likely, a new study has found.
This month has seen widespread flooding on almost every continent, from the U.S. to China, from India to Italy, in extraordinary events that climate scientists say have been made more extreme by climate change.
But research by the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences (CAS) and the UK Meteorological (Met) Office, published today in the journal Science Advances, indicates that most communities will experience even more extreme wet conditions with each degree of temperature rise.
The findings are significant not just because of flood risk: from drinking water to agriculture and hydroelectric power, a predictable supply of water is vital to practically all forms of human activity.
Using a range of methods including model simulations developed by the Met Office Hadley Centre in the U.K., the researchers found that, while average rainfall is expected to increase at a median average rate of 2.32% per degree Celsius of warming worldwide, precipitation variability will increase between 4.85 and 5.70% per degree of warming across all regions.
What does this mean?
“There is a strong indication that regions where precipitation becomes more variable will also experience more extreme rainfall,” Wenxia Zhang of the IAP and lead author of the study told me. This would mean that in areas such as northern Europe, China, central Africa and North America, “more extreme rainfall is expected under global warming with a reasonable [range of] consistency and confidence.”
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So it’s not that countries will necessarily have much more rain on average; it’s that we’ll see rain events becoming heavier and less predictable.
The research also implies that rather than floods necessarily becoming more frequent, heavier rainfall could make them more destructive.
“There should be a distinction between more frequent flooding and more extreme flooding,” Zhang said, adding that “the increase in either intensity or frequency of rainfall extremes is likely to increase the risk of flooding, but precipitation is not the only factor affecting floods.”
But if precipitation is to become more variable, couldn’t this also mean that wet regions could also see more dry spells and droughts?
“It’s hard to say,” Zhang admitted. “Based on this research, most already wet regions are expected to become wetter and more variable. Such amplified variability could mean more intense rainfall, or more dry periods, or both. It is possible—but not certain—that these regions will see more dry periods with little or no rainfall.”
Indeed, the paper also show that while wet regions will see greater variability in rainfall, some dry regions could see further extremes, with droughts potentially lasting longer. Southern Europe, including Spain, and the far north and south of the African continent are some of the regions where this could occur.
“The amplified rainfall variability manifests the fact that global warming is making our climate more uneven—more extreme in both wet and dry conditions, with wider and probably more rapid transitions between them,” Zhang said. “The resulting wider swings from one extreme to another will challenge the existing climate resilience of infrastructures, human society and ecosystems.”
Kalli Furtado, expert scientist at the Met Office and second author of the study, said the findings should send a strong signal to nations about the necessity of funding large scale climate adaptation measures—while they also imply additional difficulty in figuring out exactly what measures will be needed.
“This classification of different precipitation change regimes is valuable for regional adaptation planning,” Furtado said. “For most regions, the increasing rainfall variability, which could translate into impacts on crop yields and river flows, makes climate change adaptation more difficult.”
In the discussion segment of their paper, the authors make an unequivocal call to action to halt human-induced climate change. “As precipitation variability is projected to increase continuously with global temperature increases, international activities to reduce carbon emissions and limit global warming levels are urgently needed,” they write.
The study comes hot on the heels of a paper published this week in the journal Nature Climate Change, showing that more record-shattering weather extremes will be brought on by the rate of global warming, with “week-long heat extremes that break records by three or more standard deviations … two to seven times more probable in 2021-2050 and three to 21 times more probable in 2051-2080.”
The paper “Increasing precipitation variability on daily-to-multiyear time scales in a warmer world” can be accessed here.