A MARTÍNEZ, HOST:
A powerful storm has been soaking Northern California and Oregon this week, bringing high winds and flood risks that continue today.
MICHEL MARTIN, HOST:
It's known as an atmospheric river. A big question is whether climate change is making these storms worse.
MARTÍNEZ: Lauren Sommer from NPR's climate desk is here to explain. So, Lauren, put this storm into perspective for us. I mean, what are the impacts the West Coast is seeing now?
LAUREN SOMMER, BYLINE: Yeah. It's a really intense storm. And it's slow-moving, so that means a lot of rain. You know, atmospheric rivers are basically these plumes of moisture that move across the Pacific Ocean. And if you look at a weather map, it actually kind of looks like a fire hose is pointed at the West Coast. It's pretty narrow, so it doesn't affect the whole coast. These storms are important. They're how California gets as much as half of its rainfall every year, so they carry a lot of moisture. And this one has been affected by another weather system nearby, which is a bomb cyclone.
MARTÍNEZ: Bomb cyclone - love the term. I don't know if I like what happens after a bomb cyclone. What's - what is the actual term for a bomb cyclone, though?
SOMMER: Yeah, OK. So technically, it's bombogenesis.
MARTÍNEZ: That's better. That's a better name.
SOMMER: Yeah. It's basically when there's a rapid drop in air pressure in a short period of time. And that means the storm is intensifying, so higher winds and more rain. And some parts of the West Coast are expected to see up to 16 inches of rain when this storm is finally done. It's causing flood warnings on some rivers, although it is pretty early in the season, so rivers are low for the most part. And that means there's more room to absorb that water.
MARTÍNEZ: All right. So climate change is influencing storms like hurricanes. Is it making atmospheric rivers like this one worse?
SOMMER: So atmospheric rivers are a regular thing on the West Coast, right? But the role climate change is playing is actually a really big question that scientists are trying to sort out, because as the planet warms up, it does make rainfall more intense. There's more evaporation and warmer air can hold more moisture, so storms just, you know, have more to work with. That's very clear in the Midwest and the Northeast, where rainstorms are already dropping more rain on average. But, you know, I talked to a scientist who has analyzed storms on the West Coast - Park Williams, who is a professor at the University of California, Los Angeles. And he found so far, storms are not dropping more rain than they used to in California.
MARTÍNEZ: Not dropping more rain. Why is that?
SOMMER: Yeah. He says while there is more water vapor that can fuel those storms, there's been this circulation pattern in the atmosphere that's swept a lot of it to other places. So it hasn't resulted in heavier rainfall on the West Coast overall. But by the second half of this century, that will probably change if the planet heats up even more with climate change.
PARK WILLIAMS: It's important to be mindful that we expect precipitation events in the Western U.S. to get more intense in the future. We should be planning for that. And so the fact that we haven't seen it yet doesn't mean we shouldn't be preparing for it to occur.
SOMMER: You know, even today's storms can already cause dangerous levels of flooding. That happened in California in 2023. And so our infrastructure - you know, roads and storm drains and flood channels - it already gets overwhelmed in certain years. So there's a lot to address here, even when you take climate change out of the picture.
MARTÍNEZ: All right. That's Lauren Sommer from NPR's climate desk. Lauren, thanks.
SOMMER: Yeah, thank you. Transcript provided by NPR, Copyright NPR.
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