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article imageAnthropogenic climate change linked to Louisiana floods in August

By Karen Graham     Sep 7, 2016 in Environment
Baton Rouge - The three-day extreme precipitation event that inundated southern Louisiana with 25 to 50 inches of rainfall in August was made more likely because of human-caused climate change, according to a fast-tracked study.
In research released on Wednesday, human-caused climate change played a major role in the devastating storm that brought upwards of three feet of rain to coastal Louisiana between August 12 through 14. The deluge triggered floods that killed 13 and left thousands more homeless.
The unprecedented amounts of rain that fell stunned the weather experts, and even though these extreme weather events are supposed to be rare, they have grown increasingly common in the last century since humans have been influencing the climate.
Estimated precipitation amounts
Estimated precipitation amounts
Climate Central
The probability of these extreme precipitation events occurring again has risen 40 percent, and it may be even higher, according to the study from the National Oceanic and Atmospheric Administration (NOAA) and the World Weather Attribution (WWA) group, reports Time.
"This is a storm that's going to be studied for years to come," Barry Keim, the Louisiana state climatologist and a professor at Louisiana State University, told Discovery Seeker. Keim was not involved in the study.
Basically, we know that ever increasing greenhouse gas levels (carbon dioxide and ozone) in the atmosphere change the way the sun warms the Earth. It's a process called radiative forcing. When the sun's rays hit the planet, some of the heat is absorbed into the ground and some rays are captured by greenhouse gasses, ozone and dust particles in the atmosphere. What's left over is bounced back into space.
Human activities such as burning coal and oil inject additional CO2 into the atmosphere  which acts ...
Human activities such as burning coal and oil inject additional CO2 into the atmosphere, which acts as an extra blanket to trap solar radiation, worsening the "greenhouse effect"
Mujahid Safodien, AFP/File
Ever since the start of the Industrial Age, increasing levels of carbon dioxide and other greenhouse gasses have been capturing more and more solar radiation, in turn increasing their concentrations in the atmosphere. "They trap heat in the atmosphere, and by warming the atmosphere, they make the atmosphere hold moisture," said co-author Gabriel Vecchi of the GFDL laboratory.
"And if the atmosphere holds more moisture, it can rain more," said Karin Van der Wiel, another GFDL researcher. The researchers pointed out that their study focused on the rainfall amounts and not the flooding. This is because the U.S. Geological Survey has had teams out measuring floodwater heights and the data is still being compiled.
The research team also points out that rainfall estimates are for the whole region and not just individual locations around Baton Rouge. The report takes into account the whole central Gulf Coast area, described as being between Galveston, Texas, and Biloxi, Mississippi, and notes that extreme rainfall and flood events like the one in Louisiana are now occurring at least once every 30 years, and often, more than that.
Rivers left their banks in the historic deluge.
Rivers left their banks in the historic deluge.
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"We're trying to produce information of the highest scientific quality while at the same time doing it in a relatively timely manner," Vecchi said. The data on which the paper's conclusions are based will also be available, through a link in the online paper.
The study, "Rapid attribution of the August 2016 flood-inducing extreme precipitation in south Louisiana to climate change," was published as an open-discussion paper in the journal Hydrology and Earth System Sciences on September 6, 2016. (The paper is under review for the journal Hydrology and Earth System Sciences).
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