Climate Change A Factor In Historic Midwest Floods

Mar 24, 2019

Nebraska is facing more than one billion dollars in damage due to historic and devastating flooding this past week. The storm that set things into motion was powerful –a so-called bomb cyclone. But the amount of rain it delivered doesn’t account for the flooding on its own.

This past fall and winter were among the wettest on record for Nebraska.  So, that rain fell on frozen, water-logged ground. Instead of soaking in, it ran straight into already full rivers. Some have called the result Biblical. And anytime these kinds of superlatives come into play, one of the first questions that arises is: Is this climate change?

Kevin Trenberth of the National Center for Atmospheric Research dissects the perfect storm that led to historic flooding in the Midwest. He says climate change played multiple roles in making the storm bigger and stronger, and making the ground beneath it less able to soak up water.

“There's been record amounts of snow fall occurring before it gets to the Great Plains, but indeed the winter as a whole - December, January, February - was the wettest on record for the United States and this is exactly the sort of thing we do expect with climate change,” Trenberth said. “Oone of the reasons is because the air is a bit warmer, therefore it can hold more moisture.”

One of the consequences of that, he further explained, is that some of what would have fallen as snow has instead fallen as rain, which is one of the factors of some of the flooding that Nebraska is seeing. If it had fallen as snow, it would have sat for a while and then melted instead.

It's a complicated situation with a number of factors at play.  

The recent bomb cyclone that hit the U.S. is another weather event with different factors. The storm had pressure readings comparable to a category 2 hurricane and wind speeds close to 100 miles an hour. Trenberth says that the track of the storm can probably be blamed on El Nino, but a colder ground temperature, which makes rain less likely to be absorbed, it likely due to climate change.

“Normally you would have a snow cover and that actually keeps the ground warmer and surprisingly perhaps, in the absence of snow, the ground can indeed cool often and freeze more,” Ternberth said. “So this is a factor in the way in which – the weird way – global warming can perversely affect things.”

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