Sunday, March 13, 2016

Epic Louisiana Floods Are Part Of A Sad New Normal

Severe flooding in Louisiana. Photo from
Vernon, Louisiana Parish Sheriff's office.  
Once again, I find myself writing about unprecedented floods.

Rivers in and near Louisiana this weekend are cresting at record levels after as much as 23 inches of rain fell in just a few days. The rain, while still coming down, but it is finally tapering off.

However, flood crests will take some time to move downstream along rivers, so the already intense destruction will get worse.

At least six people have died in the flooding so far, the Weather Channel reports. 

Once again, we had the sad spectacle of people and animals being rescued from roofs, as television station WWL in New Orleans reports. 

You can watch an AP video of a helicopter flood rescue at the bottom of this post.

The flooding hit a wide area of Louisiana, Texas, Arkansas, Mississippi and Tennessee.

This flood is yet another example of the cascading trend of more and more frequent and extreme floods in the United States and elsewhere in the world.

As the Weather Channel notes, there have now been at least a dozen major flash floods in Texas, Oklahoma, Louisiana, Arkansas and Missouri over the last twelve months.

We've had a series of so-called one in a thousand year floods that seem to come much more frequently than one in a thousand years lately. Last October, South Carolina drowned in record flooding.

In 2014, much of the Ohio River Valley got hit repeatedly. In  2013, it was large parts of Colorado. 

On and on it goes.

Climate scientists have long said global warming increases the chances of extreme floods, and they  have measured that increasing trend

Before you climate change skeptics jump on me, I'm not saying that all bad floods and solely caused by global warming.

Of course, every big flood is prompted by a specific local or regional weather pattern. Many of those weather patterns would occur with or without climate change.

For instance, the past week's floods in Louisiana were created when an upper level low pressure system parked itself over central Mexico. That's a weird place for one to set up, but it sometimes happens when there's a strong El Nino, like we're having now.

The upper low set up an atmospheric river of air from the deep tropical southwestern Caribbean Sea and sprayed that moisture like a giant firehose into Louisiana and surrounding states.

A warmer atmosphere holds more moisture than a cooler one, so as global warming continues the potential for storms to unleash heavier rain is higher than would otherwise happen decades ago.

The question you have to ask is, was this Louisiana flood, and the ones I mentioned earlier, made worse by global warming?

In the case of the Louisiana flood, I have no friggin' idea. Maybe, maybe not. People smarter than me will have to analyze that.

Scientists and most journalists have rightly included the disclaimer in their reports on specific extreme events, like the Louisiana floods, that you can't really prove global warming had a hand in these disasters.

But can you, sometimes?

Yes, I know, as noted above, no weather event has a single cause. It's usually a lot of causes.

However, the National Academy of Scienes last week issued a report called "Attribution Of Extreme Weather Events In the Context of Climate Change."

In this report, the scientists note a growing ability to figure out if some weather events were indeed influenced or made worse by climate change.

As the Washington Post reports:  "This can be done by observing how far a single event, like a heat wave, is outside the norm of prior events, or by using computer models to determine how often an event like it would occur with or without human greenhouse gas emissions, (which can be included or excluded from the model.)"

 This nascent scientific approach so far seems to work best when studying heat waves, floods and some large scale storms, and less well with smaller scale disasters, like tornadoes.

No, I don't know if this past week's Louisiana flood disaster was influenced by global warming or not. But it looks like some smart scientists will study it, and maybe give us an answer to this questions.

Here's that footage of the Louisiana National Guard rescuing people from the flood:

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