(CNN) —
Climate change is partly to blame for the record rainfall that fell over Texas and Louisiana in the days after Hurricane Harvey’s landfall on August 25, according to new scientific analysis.
Human-caused climate change made the rainfall from Harvey, which dumped more than 19 trillion gallons of water and brought devastating floods to the Houston area, roughly three times more likely to occur and 15% more intense, according to World Weather Attribution (WWA), an international coalition of scientists led by nonprofit scientific research group Climate Central, in a report published Wednesday.
The question of whether climate change played a role in the disaster came up almost immediately, as it so frequently does after extreme weather events.
It was assumed that climate change contributed to Harvey’s rainfall, as intense rainfall events are one of the most often cited consequences of a warming climate. The observational data and computer models used in this study supported that assumption.
As air temperature warms, it can hold more moisture (about 7% more per degree Celsius of warming), which means there is more water vapor in the air that can be squeezed out as rainfall in a world warmed by climate change.
Other factors, such as changes in upper level winds and sea level rise can also contribute to increased flood events.
The WWA study examined extreme precipitation events in the US Gulf Coast region since 1880 and found “a clear positive trend between 12% and 22%.” Using computer models loaded with this data and comparing it to similar models that do not show the climate warming, the authors attempted to quantify the role that the warming climate had on the 2017 event.
Harvey, which rapidly intensified to a Category 4 storm just before landfall near Corpus Christi, Texas, stalled after it moved inland and remained nearly stationary for four days. This allowed rainfall totals to add up in and around Houston, reaching levels never before seen in a landfalling tropical system.
Cedar Bayou, about 30 miles east of Houston, recorded 51.89 inches of rainfall by the morning of August 31. That eclipsed the 48-inch rainfall record from Tropical Storm Amelia in 1978 and set a new record for the continental US.
The biblical flooding across Harris and surrounding counties required more than 120,000 people to be rescued or evacuated, and about 80 people died.
Though the economic impact from Harvey is still being calculated, “it is likely a $100 billion disaster,” according to Adam Smith, lead researcher at the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information.
“Harvey is the closest modern disaster comparison we have in relation to Katrina in terms of damage costs,” Smith told CNN.
Photos: Hurricane Harvey slams Texas
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Paul Jordan Anderson/DoubleHorn Photography
Downtown Houston is seen behind the flooded Buffalo Bayou a few days after Hurricane Harvey came ashore in August 2017. The Category 4 storm caused historic flooding. It set a record for the most rainfall from a tropical cyclone in the continental United States, with 51 inches of rain recorded in areas of Texas. An estimated 27 trillion gallons of water fell over Texas and Louisiana during a six-day period.
Photos: Hurricane Harvey slams Texas
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Jack Fischer/NASA
NASA astronaut Jack Fischer photographed Hurricane Harvey from the International Space Station.
Photos: Hurricane Harvey slams Texas
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Joe Raedle/Getty Images
Steve Culver comforts his dog Otis in the hurricane aftermath. Harvey destroyed most of his home in Rockport while he and his wife were there.
Photos: Hurricane Harvey slams Texas
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David J. Phillip/AP
Houston police officer Daryl Hudeck carries Catherine Pham and her 13-month-old son, Aiden, after rescuing them from floodwaters.
Photos: Hurricane Harvey slams Texas
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William Luther/San Antonio Express-News via ZUMA Wire
A damaged home is seen in the Key Allegro neighborhood of Rockport.
Photos: Hurricane Harvey slams Texas
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Charlie Riedel/AP
A car is submerged by floodwaters on a freeway near downtown Houston.
Photos: Hurricane Harvey slams Texas
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Nick Wagner/Austin American-Statesman via AP
Melani Zurawski cries while inspecting her home in Port Aransas, Texas.
Photos: Hurricane Harvey slams Texas
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BRENDAN SMIALOWSKI/AFP/Getty Images
A graveyard is flooded in Pearland, Texas.
Photos: Hurricane Harvey slams Texas
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Timothy Fadek/Redux for CNN
Soldiers with the National Guard patrol Rockport, looking for residents trapped in their homes.
Photos: Hurricane Harvey slams Texas
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BRENDAN SMIALOWSKI/AFP/Getty Images
Evacuees are loaded onto a truck in Houston.
Photos: Hurricane Harvey slams Texas
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Charlie Riedel/AP
People push a stalled pickup through a flooded street in Houston.
Photos: Hurricane Harvey slams Texas
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Timothy Fadek/Redux for CNN
Rockport residents return to their destroyed home.
Photos: Hurricane Harvey slams Texas
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David J. Phillip/AP
Rescue boats fill Tidwell Road in Houston as they help flood victims evacuate the area.
Photos: Hurricane Harvey slams Texas
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Joe Raedle/Getty Images
People wait to be rescued from their flooded home in Houston.
Photos: Hurricane Harvey slams Texas
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Tony Gutierrez/AP
Volunteers in Dallas organize items donated for hurricane victims.
Photos: Hurricane Harvey slams Texas
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Timothy Fadek/Redux for CNN
When Harvey slammed the Texas coast and flooded much of Houston, volunteers sprang into action. Some came from as far away as the Florida Everglades, boats in tow, ready to rescue people trapped in their homes.
Photos: Hurricane Harvey slams Texas
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Erich Schlegel/Getty Images
Larry Koser Jr. and his son Matthew look for important papers and heirlooms inside a flooded home in Houston.
Photos: Hurricane Harvey slams Texas
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Alyssa Schukar/The New York Times/Redux Pictures
Members of the National Guard rest at a furniture store in Richmond, Texas.
Photos: Hurricane Harvey slams Texas
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Joe Raedle/Getty Images
Volunteer rescue workers help a woman from her flooded home in Port Arthur, Texas.
Photos: Hurricane Harvey slams Texas
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Marcus Yam/Los Angeles Times/Getty Images
This aerial photo shows flooded residential neighborhoods in Houston.
Photos: Hurricane Harvey slams Texas
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Michael Ciaglo/Houston Chronicle/AP
Tammy Dominguez and her husband, Christopher, sleep on cots at the George R. Brown Convention Center, where thousands of people were taking shelter in Houston.
Photos: Hurricane Harvey slams Texas
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Nick Oza/USA Today Network/Sipa USA
An elderly patient waits to be rescued from the Gulf Health Care Center in Port Arthur. The facility was evacuated with the help of first responders and volunteers.
The WWA study looked only at the role climate change played in the amount of rainfall Harvey produced, ignoring other variables that made Harvey so exceptional, such as the rapid intensification before landfall and the unusual lack of movement it had in the following days.
“It’s clear that Harvey’s exceptional rainfall was due to the stalling and looping nature of the track of the storm – which this study does not address in the slightest,” Ryan Maue, a meteorologist with weather.us who was not affiliated with the study, told CNN.
But that doesn’t mean Maue is refuting its conclusion.
“There’s little doubt that global warming has and will continue to enhance rain rates and intensity, but it’s not clear that this paper has teased out all of the possible mechanisms that led to Harvey’s extreme flooding impacts,” Maue said.
