Human-driven climate change made the extreme rainfall that caused dozens of deaths in early April in the U.S. South and Midwest more intense and likely, according to a new rapid analysis from World Weather Attribution (WWA).
The storms that struck from April 2-6 caused flash floods, tornadoes and power outages, affecting at least 100,000 people. Some areas received more than 400 millimeters (16 inches) of rain, considered the worst ever recorded in the region, WWA said in its report. WWA is a global initiative that analyzes the role of climate change in extreme weather events.
During a media briefing, Shel Winkley, a weather and climate engagement specialist at the nonprofit news platform Climate Central, called the April storms “a very interesting event where weather and climate change collided together.”
By April 2, the National Weather Service’s offices sent out 728 warnings of severe thunderstorms and tornadoes, the third-highest count on record, Winkley said.
By analyzing weather and climate model data, the WWA researchers found that climate change made the heavy rainfall in the region 40% more likely and 9% more intense than in preindustrial times. In today’s climate, extreme rainfall events like the one in April are still relatively rare, expected to occur only once every 90-240 years, the authors write. However, in the preindustrial era, which was 1.3° Celsius (2.3° Fahrenheit) cooler, such extreme rainfall would have been even rarer, they add.
Ben Clarke, study co-author from Imperial College London’s Centre for Environmental Policy, said at the briefing that the “40% more likely, 9% more intense” analysis was already a “conservative estimate” based on their climate models’ mixed results. “However, in spite of that, when we combine the evidence, we do find an overall increasing trend in such extremes.”
Clarke said sea surface temperatures in the Gulf of Mexico at the beginning of April “were about 1.2°[C, or 2.2°F] hotter than they would have been without anthropogenic emissions.”
“We conclude that present warming of 1.3°[C] did amplify the extreme rainfall leading to flooding in this region,” he said. “And then finally, that we have a really strong and robust warming of the Gulf of Mexico, which we know also played a role in the event.”
If our planet warms by about 2.6°C (4.7°F) by 2100, which some climate models project, extreme rainfall events like the one in April are expected to double in likelihood again, and further increase in intensity by roughly 7%, the study said.
The scientists also highlighted at the briefing how early warnings from the NWS saved lives in April. They further warned that layoffs can impact the agency’s ability to keep people safe. Bernadette Woods Placky, chief meteorologist at Climate Central, said 30 out of 122 NWS offices were without a meteorologist-in-charge that time.
Banner image of severe thunderstorms over the central and southern U.S., by NOAA Satellites via Twitter.
Credits
