Doyle Rice

USA TODAY

Climate change played a major role in the historic rainfall that caused catastrophic flooding in Louisiana last month, nearly doubling the chance of such a deluge taking place, according to a fast-tracked federal report released Wednesday.

Many spots picked up more than 2 feet of rain in the state, which was drenched by some 7.1 trillion gallons of water, three times the amount Hurricane Katrina dumped there in 2005. Some 30,000 people needed to be rescued from floodwaters that killed 13 people and damaged 60,000 homes in what the Red Cross called the nation's worst natural disaster since 2012.

Human-caused, heat-trapping greenhouses played a "measurable" role in the colossal rainfall totals, which were fueled by high humidity and a stalled storm system above the Gulf Coast, said Karin van der Wiel, a scientist from the National Oceanic and Atmospheric Administration (NOAA) and the report's lead author.

The burning of fossil fuels such as oil, gas and coal releases greenhouse gases such as carbon dioxide into the Earth's atmosphere, which has warmed to levels that cannot be explained by natural variability, scientists say. Rainfall patterns and humidity levels are also affected by this process, as warmer air can hold additional amounts of water vapor.

Computer models analyzed the amount of rain that caused the flooding, van der Wiei said. The rainfall Louisiana experienced "is now expected to occur at least 40% more often" than prior to the mid-1800s, the report stated.

University of Arizona climate scientist Jonathan Overpeck, who wasn't part of the report, said the study is solid.

"It is becoming more and more established that global warming is leading to more intense precipitation in many storms," he said.

The report is an example of single event attribution study released rapidly to catch the public's eye while an extreme weather event is still fresh in people's minds, NOAA said.

The information is also critical to insurers, policymakers, engineers and emergency managers to prepare for more climate change-fueled events down the road, said Heidi Cullen, chief scientist at Climate Central, an independent climate science and news organization.

The study has been submitted to Hydrology and Earth System Sciences, an interactive, open access journal of the European Geosciences Union. It is noteworthy for being the first collaboration between NOAA and scientists at the World Weather Attribution project.