Study Confirms Climate Change Intensified April Floods

Severe thunderstorms in April resulted in historic downpours and flooding across Arkansas, Kentucky, and other states, exacerbated by climate change.

This information comes from the World Weather Attributes Project, a consortium of scientists studying major weather events in relation to climate change.

From April 3 to April 6, heavy rainfall hit the southeastern U.S., leading to widespread flooding, flood warnings for over 70 million individuals, at least 15 fatalities, the sweeping away of vehicles, and train derailments.

By utilizing climate models alongside historical data, researchers examined storm systems across eight affected states and concluded that the current weather patterns were approximately 9% more intense due to global warming, with a 40% increased likelihood compared to a scenario without such warming.

Ben Clark, a researcher at Imperial College London, stated, “We conclude that the existing 1.3 degrees Celsius of warming has intensified the extreme rainfall leading to flooding in the region. A warmer atmosphere retains more moisture.”

The 1.3 degrees reference indicates how much warmer the planet has become in Celsius since humanity began releasing greenhouse gases into the atmosphere post-Industrial Revolution—a conversion of approximately 2.4 degrees Fahrenheit.

Clark noted that the probability estimates from the group are conservative. The researchers identified a unique weather configuration that contributed to the extreme rainfall.

Shell Winkley, a meteorologist with Climate Central, a nonprofit news organization involved in the report, explained that a low-pressure system interacting with a high-pressure ridge caused the thunderstorms to repeatedly affect the same areas in the Southeast and Midwest.

“This front was the route through which these storms moved, and there was also a trigger mechanism. The thunderstorms accumulated rain on already saturated soil,” Winkley noted. “This event is a fascinating intersection of weather and climate change.”

According to Winkley, the National Weather Service issued the third highest weather warning on April 2.

“By the end of the day, the National Weather Service had released 728 separate thunderstorm and tornado warnings from various offices, with numerous locations experiencing extreme rainfall between April 3 and April 6, with some areas seeing up to 16 inches,” Winkley explained.

Upon reviewing historical rainfall from April, researchers indicated that similar storm systems are anticipated every century in the current warm climate.

Gerald Brotzge, a Kentucky climatologist and professor at the University of Kentucky Western University, initially approached such studies with skepticism, particularly those linking large-scale flooding to climate change without accounting for unique weather setups. However, he found this study credible.

Brotzge remarked, “It appears they conducted a thorough analysis. In this instance, a stagnant boundary allowed thunderstorms to constantly form in the same locality—an accurate observation.”

Brotzge noted that Kentucky has warmed by nearly 1.8 degrees Celsius (approximately 3.2 degrees Fahrenheit) over the last 130 years and has been experiencing increased rainfall.

“Our annual rainfall has risen by about 10%,” Brotzge stated. “Half of our ten wettest years have occurred since 2011, with 2011 being the wettest and 2018 as the second wettest.”

The World Weather Attribution is a team of scientists who quickly assess the influence of climate change on extreme weather events. Their methodology has undergone peer review, though some analyses are not immediately reviewed. Previous studies by the group on heatwaves, wildfires, and hurricanes have also faced academic scrutiny.