Expect more intense rainfall events as the world warms, scientists say

LEILA FADEL, HOST:

Heavy rain in the Northeast this week flooded towns in Vermont, some of which were still recovering from floods over the summer.

A MARTÍNEZ, HOST:

The east coast of Australia also saw flooding after some cities got more than 30 inches of rain. These kind of events are becoming more common as the climate gets hotter.

FADEL: For more on what coming storms could look like, Lauren Sommer is here from NPR's climate desk. Good morning, Lauren.

LAUREN SOMMER, BYLINE: Morning.

FADEL: So what is happening with rainfall? How much more dangerous are storms already becoming?

SOMMER: The short answer is that, in most of the U.S., when it rains, it rains more. And extreme storms are getting more extreme. They're dropping more rain. Over the last 50 years, that's been particularly true in the Northeast and the Midwest, where those really bad storms are dropping 40- to 50% more rain.

FADEL: And do we know that climate change is already causing that?

SOMMER: Yeah. There are a lot of studies that show intensifying rainfall is mostly due to the planet getting hotter, which is happening as humans burn more fossil fuels. And that's because a hotter atmosphere can hold more moisture - more water vapor - so the storms just have more water to work with, basically.

FADEL: How much worse does rainfall get if the planet continues warming?

SOMMER: Yeah. I spoke to Megan Kirchmeier-Young about this. She's a research scientist at Environment and Climate Change Canada, which is a government agency. She says, if we stay on the current path of climate change, rainfall gets even more extreme in many parts of North America.

MEGAN KIRCHMEIER-YOUNG: Some of those changes are considerable. Events that used to be very rare, in the future, under a few degrees of global warming, will be fairly common events.

SOMMER: You know, in the southern U.S. in particular, storms could drop 20- to 30% more rain in the future, according to one study.

FADEL: What does this mean for communities in the U.S. and the flooding they could see?

SOMMER: Yeah. You know, it's a big danger because, when it rains, all that water needs to drain away, and that's handled by storm drains and other infrastructure. And when communities build that, they design it for a certain kind of storm. And if it's the storms of last century, then all that concrete around you - it's going to get overwhelmed. And that's when streets flood, basement apartments flood, people actually lose their lives. Kirchmeier-Young says that's why communities need to plan for climate change.

KIRCHMEIER-YOUNG: Our climate is not stationary. It is changing, and it's going to continue to change. And we need to understand that, and we need to consider that instead of planning for the climate we used to have.

FADEL: So how much help are cities getting in preparing for a future with more intense rain?

SOMMER: Yeah, it's actually a huge problem. It's something we've covered for years on the climate desk. A handful of cities are planning for climate change. You know, they're using the storms of the future to build infrastructure today so it's ready for that. But many cities are not. I've spoken to several that are designing for storms from 60 years ago, and that means they're at risk. The issue is that cities rely on information from the federal government to know what kind of storms to plan for. Those records are decades old for many states. They don't take climate change into account. That is changing. The National Oceanic and Atmospheric Administration is updating rainfall records currently, but, you know, it won't be ready until 2026 at the earliest. So in the meantime, communities are largely on their own.

FADEL: Thanks for this, Lauren.

SOMMER: Thank you.

FADEL: Lauren Sommer is on NPR's climate desk.

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