Report: Climate change made April flooding, severe storms 9% more intense

Yahoo

09-05-2025

Farm equipment is seen partially submerged on a flooded field in Ridgely, Tenn. on April 9, 2025. (Photo: Cassandra Stephenson)
The effects of climate change made severe flooding that inundated West Tennessee and parts of the Central Mississippi River Valley in early April about 9% more intense, according to an analysis published Thursday by an international team of environmental researchers.
From April 3 through April 6, thunderstorms and torrential downpours hovered over a broad swath of the Mississippi River Valley, leading to near-record breaking floods, widespread damage and at least 15 deaths.
Those four days of rainfall are the heaviest recorded for the region in spring since 1950, according to the report published by World Weather Attribution, an international collaboration that analyzes the potential influence of climate change on extreme weather events.
The study used observational data, historical records and climate models to examine how warming temperatures impact storm likelihood and intensity. Researchers also used nonprofit Climate Central's Ocean Climate Shift Index tool — based on observations and climate model data — to analyze sea surface temperatures in the Gulf of Mexico where much of the moisture fueling the storm originated, said Ben Clarke, a researcher at the Centre for Environmental Policy at Imperial College London.
Researchers compared how this type of weather event has changed between today's climate — about 1.3 degrees Celsius hotter due to warming caused by use of fossil fuels and deforestation — compared to a cooler, pre-industrial climate (1850-1900).
'When we combine the evidence, we do find an overall increasing trend in such extremes,' Clarke said. 'Similar events have become, we estimate, about 40% more likely, or, equivalently, about 9% more intense.'
Clarke noted that some climate models used in the study showed a more 'mixed picture' of the effects of warmer temperatures, meaning the study's results are 'likely a conservative estimate.'
While the methods used in this study are peer-reviewed, the study itself was released in the immediate aftermath of the severe weather event and has not yet been peer-reviewed itself, Clarke said.
Over four days in early April, eight states saw 'relentless amounts of rain' ranging from six to 12 inches, with some locations exceeding 16 inches, Climate Central Weather and Climate Engagement Specialist Shel Winkley said.
The rain fell on soil that was already saturated from late-winter rain, particularly in the Ohio River Valley, he said.
In Northwest Tennessee, the small town of Rives suffered severe flooding in February, only to flood again a few weeks later.
Winkley said a ridge of high pressure over the Carolinas, Georgia and Florida blocked the low pressure system producing the storm from pushing forward, essentially stalling the storm front to dump rainfall over the already-saturated ground.
Early warnings from the National Weather Service very likely saved lives, Bernadette Woods-Placky, Climate Central's chief meteorologist, said.
In Obion County, Tennessee, more than 100 families evacuated their homes during the event. Nearby Dyer County issued a mandatory evacuation for residents of Bogota on April 7 in anticipation of additional flooding.
Woods-Placky noted that layoffs and firings were beginning to roll out in National Weather Service offices across the U.S. as part of cost-cutting measures under the Trump administration around the time these floods were happening.
'This is an example of how critical these employees are and why recent workforce cuts risk undermining their ability to keep people safe and prepared,' she said.
Winkley said post-storm analyses like this are vital for protecting public safety in future events.
'It helps us really understand, is this going to be a place that's livable in the future, and if it is, how do we make sure that it's livable and safe?' he said.
The 96-hour rain event was the second-highest on record for the Obion, Forked Deer and Loosahatchie Rivers (all Mississippi River tributaries), according to the U.S. Army Corps of Engineers.
Dyersburg, Tennessee — the county seat of Dyer County — is prone to flooding from the North Fork of the Forked Deer River.
Early April's flooding marked the third-highest flood in the town's history, according to Mayor John Holden, who has held the position for 19 years.
The worst flood in Dyersburg's history occurred in 2010, wiping out multiple homes and trailer parks. The second-highest flood record was set in 1937.
Historical data indicates downpours like this are 'expected to occur, on average, about once a century in today's climate with 1.3 degrees Celsius of warming,' the report states.
Before the storms rolled in, the National Weather Service's Weather Prediction Center warned the public of 'generational' rainfall totals.
But the study's authors caution that further warming could increase the likelihood that these events will no longer be expected just once in a generation.
'If warming reaches 2.6 degrees Celsius (4.7 degrees Fahrenheit), which is expected by 2100 under current policies, four-day spells of rainfall are expected to become a further 7% more intense and twice as likely,' according to a study summary.
'This is a good moment to remember that we are a water planet, and a warmer atmosphere forces more evaporation, so our atmosphere in general has more water to come down whenever there's a trigger, wherever there's a trigger,' Woods-Placky said. 'So that's why we're seeing an overall increase in heavy rain events, even to places that may not be getting wetter. The distribution of how they're getting rain is coming in these heavier buckets.'
Tennessee, Kentucky and Arkansas were hardest hit by the early April storms, and each state requested a major disaster declaration to access FEMA assistance.
Damage estimates for public property and recovery in West and Middle Tennessee exceed $26 million, according to post-storm assessments. State and local officials believe this will meet the eligibility threshold for federal public aid. Tennessee has yet to receive a decision from the Trump administration.
The administration approved a major disaster declaration for Kentucky on April 24. Arkansas Gov. Sarah Sanders requested a major disaster declaration to cover the April storms on May 3. Trump denied Sanders' earlier request for major disaster aid following storms and tornadoes in March.
West Tennessee picks up pieces, awaits FEMA decision after severe storms
The Tennessee Emergency Management Agency estimates around 300 homes and 14 businesses or nonprofits were severely damaged. West Tennessee mayors report hundreds of acres of flooded farmland.
To illustrate the significance of the storm's 9% higher intensity that the study attributes to climate change, Imperial College London Centre for Environmental Policy Senior Climate Science Lecturer Friederike Otto refers to a separate study on Hurricane Helene.
That study, published by the Grantham Institute of Climate Change and the Environment in 2024, estimated that a roughly 11% increase in wind speed due to climate change accounted for about 44% of the storm's damage in coastal Florida.
Essentially, Otto said, the increase in intensity by 10% could nearly double the cost of damage.
'If that hits you (the region) once in a lifetime, I mean … that's one thing,' Otto said. 'But if that hits you twice, and it has the higher impact, that completely changes what … extreme weather can mean for a community.'
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