A new federal study has found that manmade climate change about doubled the chances for the type of heavy downpours that caused devastating Louisiana floods last month, The Associated Press reports.
Using two different sets of measurements and computer model runs simulating thousands of years, scientists found a clear sign of global warming in the rain that triggered the flooding that killed at least 13 people, damaged 150,000 homes and cost at least $8.7 billion.
More than 26 inches of rain fell in one week, with nearly a foot in just one day, the National Oceanic and Atmospheric Administration says.
The study—a collaboration by NOAA’s Geophysical Fluid Dynamics Lab, Princeton University, the Dutch weather agency and the private science-and-journalism group Climate Central—has not been peer reviewed yet because the downpour occurred less than one month ago.
Still, it has been accepted by the journal Hydrology and Earth System Sciences and will be peer reviewed live online over the next couple months.
“The global warming signal is present in these numbers,” says study lead Karin van der Wiel, an NOAA and Princeton University researcher and meteorologist. “For a precipitation event of this size to occur on the central Gulf Coast, the odds have increased by at least 40% and most likely doubled.”
After the floods, the question raised was: Did global warming play a role?
Climate Central’s World Weather Attribution team brought in NOAA and others because of their high-quality computer models that had already been running data, says Climate Central chief scientist Heidi Cullen.
The computer simulations run over and over again, comparing scenarios in which man-made greenhouse gases trap heat and others mirroring current conditions and other scenarios.
The scientists concluded that the odds of such downpours increased anywhere from 30% to more than 240% due to climate change. van der Wiel says they can see at least a 40% increase.
“We are now actually able to objectively and quantifiably say ‘yes, climate change contributed to this event,'” Cullen says of the Louisiana downpours. “It’s unequivocal.”
National Center for Atmospheric Research senior scientist Kevin Trenberth says the study seems to come to the right conclusions, but misses the role of super warm seawater and “off the charts” moisture in the air, some of which was natural due to El Nino and about one-third from man-made climate change.
