Our current climate brings plenty of disastrous examples of extreme rainfall. Floods have caused death and displacement around the world, from Sri Lanka to Colombia. In Canada, British Columbia’s unprecedented heavy rains caused mud- and rockslides, putting the province into a state of emergency and displacing 18,000 residents. Germany experienced its worst flooding in 200 years, which killed more than 150 people.
Scientists later found the German floods were up to nine times more likely due to climate change. The heating of the globe—caused by the burning of fossil fuels—intensifies rainfall. Most industries, like agriculture, benefit from more annual precipitation. But a new study has found that as the number of rainy days increases—both in the form of extreme rain and gentle drizzles—economic growth slows. And it found that the impact was more pronounced in wealthier countries. Those effects will likely continue to worsen until the world reaches net-zero emissions.
“The biggest problem of climate change will be, and already is, the increase and intensification of weather extremes,” says Anders Levermann, professor of dynamics of the climate system at the Potsdam Institute for Climate Impact Research in Germany. “And rainfall is a huge part of this.”
The globe’s temperature has risen about 1 degree Celsius (roughly 2 degrees Fahrenheit) since 1880, but it’s been rising at double the previous rate since about 1981. And with each degree it climbs, precipitation increases by about 7%. That’s because a warmer atmosphere can simply hold more water vapor. Separately, more evaporation from the ocean occurs when it’s warmer, and that water must eventually return to the earth.
Levermann is one of the authors of the study, which examines economic output data from 1,554 regions across 70 countries from the 40-year span of 1979 to 2019. First they looked at annual mean precipitation, finding that an increase had a positive effect on economic growth rates. That seems to make sense because farming needs more water throughout the year, as do other industries. “This is consistent with the interpretation of net water supply as an economic good,” the study reads.
However, when researchers looked at daily rather than annual rainfall, the results differed. First, as the extreme daily rainfall—when precipitation is dangerously high—increased, economic growth rates were negatively impacted. Again, that makes sense: Extreme rainfall can cause floods, such as those seen around the world last year, which slow the economy. Levermann clarifies that the study didn’t assess the short shocks of flood destruction, which are also harmful, rather the effect on economic output. “It’s the perturbation of the normal flow of things,” he says.
What makes the finding even clearer is that economic growth also slowed with an increase in the number of “wet days,” defined as any day with more than 1 millimeter of rain. “That’s really little rainfall,” Levermann says. “It’s hardly measurable.” Still, that light rain resulted in strong reductions in growth rates.
“It’s quite natural that extreme rainfall events will perturb our daily life,” Levermann says. “But what I think is surprising is that if we have more rainy days, that normal drizzle will harm our economy.”
The study also examined individual sectors, finding that even the services and manufacturing industries slowed due to more days with light rain. Increased rain may cause transport delays, for instance, leading to postponements in package deliveries, or in employees not being able to get to work on time. While those effects may seem trivial, Levermann notes that “We’re talking about percentages here, which are relevant because that’s what we rely on. We think it’s a bad year if we have 1% less economic growth.”
Perhaps surprisingly, researchers also found the increase in rainy days affected richer economies more. We may tend to think they’re more resilient, but perhaps because systems are so automated and efficient, they leave little room for adaptation to “small grains in the machinery,” Levermann says, adding, “We are confident in the rich countries that nature cannot really disturb us. And that’s not true.”