How climate disruption increases extreme weather

https://www.npr.org/2018/07/29/633203732/when-the-weather-is-extreme-is-climate-change-to-blame

Laurel Wamsley
July 29, 2018

Dramatic weather events happened this past week in many parts of the Northern Hemisphere. There were wildfires in Greece, Scandinavia, and the Western U.S. Flooding followed record rainfalls in the Northeast. And dangerous heat waves settled over the Southwest, Japan, and the U.K.

If it continues like this, 2018 could end up being one of the hottest years on record.

When the news is full of stories on extreme weather, it's hard not to wonder: Is this what climate change looks like?

Climate scientists say yes — though it's complicated.

Take wildfires, for example.

"We see five times more large fires today than we did in the 1970s," says Jennifer Balch, professor in geography and director of Earth Lab at the University of Colorado Boulder.

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"Fire season is about three months longer than it was just a few decades ago," she says. "We've seen a 2-degree Fahrenheit increase across the Western U.S. Snowpack is melting earlier, and what that's doing is essentially opening up the window for fires to happen over a much longer period of time."

Last year was the costliest fire season ever, with damages exceeding $18 billion dollars.

Overall, weather and climate disasters in the U.S. caused more than $300 billion in damages in 2017, shattering previous records. Though that's not all climate — those increased costs are partly the result of development and sprawl.

Andreas Prein is a research scientist at the National Center for Atmospheric Research in Boulder, Colorado. He studies how extreme weather — especially thunderstorms and heavy downpours — might change in the future.

"What we see from climate change is that you lose a lot of these very moderate and light rainfall storms and replace it with very intense storms," he says. Over the last 50 years, the number of really big rainstorms has increased by as much as 70 percent.

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Some aspects of climate change are pretty certain, he says. Temperatures are rising. Rainstorms and heat waves are getting more intense. These are the long-predicted results of increased greenhouse gas emissions.

To a certain degree, that we've had so much extreme weather this past week is a coincidence: fires, heat waves, and rainstorms happen every summer.

But climate change makes this kind of extreme weather more common, researchers say – and it's a trend that's expected to continue as the planet keeps getting warmer.