Extreme Floods May Be the New Normal

http://www.scientificamerican.com/article/extreme-floods-may-be-the-new-normal/?WT.mc_id=SA_BS_20160819

By Erika Bolstad, ClimateWire on August 18, 2016

Over the past year alone, catastrophic rain events characterized as once-in-500-year or even once-in-1,000-year events have flooded West Virginia, Texas, Oklahoma, South Carolina and now Louisiana, sweeping in billions of dollars of property damage and deaths along with the high waters.

These extreme weather events are forcing many communities to confront what could signal a new climate change normal. Now many are asking themselves: Are they doing enough to plan for and to adapt to large rain events that climate scientists predict will become more frequent and more intense as global temperatures continue to rise?

The answer in many communities is no, it’s not enough.

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One of the first shifts that must happen, many experts in hazard mitigation say, is to stop using the climate of the past to plan for the future.

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The 39-hour rain event in Louisiana, which killed at least nine people and flooded upward of 40,000 homes, was a radical weather system that would have done plenty of damage, global warming or no. The same was true for a July 30 flash flood in Ellicott City, Md., which killed two people and swept a wave of destruction through the historic downtown when 6 inches of rain fell over several hours.

Yet climate change also likely played a role, if mostly to intensify the amount of rainfall because of an increased amount of water vapor in the atmosphere caused by higher temperatures.

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What climate scientists do know is that the intensity of extreme precipitation events is on the rise.

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Climate change could expose vast swaths of U.S. infrastructure to additional natural hazards that are likely to intensify as sea levels rise, temperatures increase and precipitation patterns shift, the report found. Power transmission lines, ports, refineries and wastewater treatment facilities across the country are vulnerable to climate change.

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http://www.scientificamerican.com/article/why-the-deadly-louisiana-flood-occurred/

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The frequency and intensity of heavy rainfall events have increased globally, said Kenneth Kunkel, a climate scientist at NOAA’s National Centers for Environmental Information.

“Each decade, it has been higher than the previous decade, for about the last 30 to 40 years,” he said.

Both the land and the oceans have been warming up, which has increased the amount of water vapor in the atmosphere, he said. The oceanic moisture feeds into the storms that form over land. It is likely that the storm in Baton Rouge last week produced more rainfall than it would have 40 years ago, Kunkel said.

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tags: extreme weather, severe weather