How global warming boosted yet another ‘500-year storm’ in Louisiana


If you’ve watched the news out of Louisiana this weekend, you’ve surely seen clips of the epic flooding in my native state. Entire communities submerged. Heroic rescues of people and their pets from their submerged vehicles or the roofs of their homes. Even Louisiana’s governor, John Bel Edwards, had to leave the governor’s mansion because the basement was filled with chest-deep water and the electricity is out.

“Oh my God, I’m drowning,” one woman yelled from her almost fully submerged car right before police amazingly pulled her to safety. Others were not so lucky; authorities have confirmed three deaths so far, and there are fears the toll will rise before the waters fully subside.

And more rain is in the forecast for parts of the state. Here’s a summary of some of the worst flooding in the history of my low-lying state:

In Baker, just north of Baton Rouge, residents were rescued by boats or waded through waist-deep water to reach dry ground. Dozens of them awoke Saturday morning on cots at a makeshift Red Cross shelter only a few blocks from their flooded homes and cars.

Shanita Angrum, 32, said she called 911 on Friday morning when she realized flood waters had trapped her family in their home. A police officer carried her 6-year-old daughter, Khoie, on his back while she and her husband waded behind them for what “felt like forever.”

“Snakes were everywhere,” she said. “The whole time I was just praying for God to make sure me and my family were OK.”

Beginning Friday, 6 to 10 inches of rain fell on parts of Louisiana and several more inches of rain fell on Saturday, according to the National Weather Service. Some areas got even more rain. In a 24-hour period, Baton Rouge had as much as 11 inches while one weather observer reported more than 17 inches in Livingston.

Forecasters expected a turn to the north Sunday by the system, warning portions of central and northern Louisiana could see heavy rain into next week.

Flooding, of course, is nothing new in Louisiana, where some major population centers are below sea level. Our long network of levees is a testament to humankind’s efforts to tame the raging waters of the Mississippi and its tributaries. But weather experts are saying the current deluge tracks with what should be a one-in-a-lifetime event, a so-called “500-year storm.” The only problem is that such events are now taking place all across America all of the time. While every storm has its unique characteristics, climate watchers say that factors associated with global warming are giving the recent batch of bad weather its unusual strength.

On August 11, a measure of atmospheric moisture, precipitable water, was in historic territory at 2.78 inches, a measurement higher than during some past hurricanes in the region. Increased moisture in the air and unusually heavy rainfall are classic signals of climate change. As the world warms, storms are able to feed on warmer ocean waters, and the air is able to hold and dump more water. These trends have led to a pronounced increase in intense rainfall events and an increase in flooding risk. In the Southeastern US, extreme precipitation has increased 27 percent from 1958 to 2012.

As the piece in Climate Signals notes:

One of the clearest changes in weather globally and across the United States is the increasing frequency of heavy rain.[4] A warmer atmosphere holds more water vapor. And like a bigger bucket, a warmer atmosphere dumps more water when it rains. The storm in the Southeastern US was supercharged by running over a warmer ocean and through an atmosphere made wetter by global warming.

Climate change is now responsible for 17 percent of moderate extreme rainfall events, i.e. one-in-a-thousand day events.[5] The more extreme the event, the more likely climate change was responsible, as climate change affects the frequency of the extreme events the most. In the instance of a one-in-a-thousand year event, the odds that climate change was responsible is dramatically higher.[5]

Indeed, these kind of storms are now all too common:

Today’s rainstorm in Louisiana is at least the eighth 500-year rainfall event across America in little more than a year, including similarly extreme downpours in Oklahoma last May, central Texas (twice: last May and last October), South Carolina last October, northern Louisiana this March, West Virginia in June, and Maryland last month.

And these were just the events that the agency decided to write a report on. One notable exception to this list is the Tax Day flood in the Houston metropolitan area this April, at least the fourth major flood in that region in a span of a year. The local flood control district extrapolated the 23.5 inches of rain over 14.5 hours in Pattison, Texas, during the Tax Day storm to be a one-in-10,000-year event.

Statistical calculations like these make a major assumption: That the climate of the past is the same as the climate of today. That’s no longer a very good assumption.

Indeed, the situation in Louisiana could almost be described as ironic, given the longtime dependence of the state’s economy on fossil fuels like oil and natural gas — the biggest contributors to greenhouse-gas pollution that in turn creates man-made climate change. But rather than ponder those ironies, we should be spurred to action. Efforts to protect and reclaim Louisiana’s wetlands — meant to absorb storms like a sponge — are more critical than even. The next “500-year storm’ could be only months away.

Read more about this week’s historical flooding from the Chicago Tribune:

For additional information on the Louisiana floods and climate change, check out:

Check our more about the recent spate of flooding and global warming here:

Learn more about the need for worldwide action on fossil fuels in my new book, Crude Justice: How I Fought Big Oil and Won, and What You Should Know About the New Environmental Attack on America

© Stuart H. Smith, LLC 2015 – All Rights Reserved

Add comment

Stuart H. Smith is an attorney based in New Orleans fighting major oil companies and other polluters.
Cooper Law Firm

Follow Us

© Stuart H Smith, LLC
Share This