ARI SHAPIRO, HOST:

Floridians have been preparing for the worst, filling sandbags, bagging up mementos and inching along Florida's highways to heed evacuation orders. It's the second time in as many weeks that high winds, huge storm surges and driving rain have threatened the residents of the sunshine state. NPR climate editor Rachel Waldholz has been looking into how a warming planet contributes to these storms and what climate change could mean for the future of catastrophic weather events. Hi, Rachel.

RACHEL WALDHOLZ, BYLINE: Hi, Ari.

SHAPIRO: First Helene, now Milton. Are these two massive hurricanes in just about two weeks evidence that we are seeing more frequent storm activity than in the past?

WALDHOLZ: So actually, no, we haven't seen an increase in the number of hurricanes hitting the U.S. But climate change is making many storms more intense, so more powerful, with way more rain, more dangerous storm surge, more flooding. And so while the total number of hurricanes isn't increasing, dangerous storms are becoming more common. And that can definitely make it feel like we're getting more overall.

SHAPIRO: So let's get to the climate change piece of this. We know that a warming planet includes warming oceans. Explain why warming oceans helped a storm like Milton explode into a Category 5 as it moved across the gulf before eventually weakening.

WALDHOLZ: Yeah, exactly. So temperatures in the Gulf of Mexico right now are well above normal, and that hotter ocean water is fuel for more powerful storms. Basically, when the water is warmer, storms can suck up way more of that moisture, and that then falls as heavier rain. And as we saw with Helene, that rain and flooding can be some of the most devastating part of a storm. But that heat and moisture also serves as energy for the storm, and so it makes it much more likely that we'll see the kind of rapid intensification that we saw both with Helene and now with Milton, where storms get really, really big, really fast. And that's especially dangerous because it makes it much harder to prepare and evacuate in time.

SHAPIRO: OK, so warm oceans translate to stronger storms. But there's another element here, which is that climate change adds to sea level rise, which can create a bigger storm surge, right? Explain that.

WALDHOLZ: Yeah, so climate change is driving rising sea levels. And some of the fastest rates of sea level rise in the world actually are along the Gulf Coast. So that's driven by melting ice on land, like the Greenland ice sheet. But also, as water gets warmer, it expands. So then when a storm like Milton comes along driving this huge wall of water in front of it, and water levels are already higher than they used to be, that's a recipe for really catastrophic storm surge. And right now, we're seeing predictions of 15 feet of storm surge in some places.

SHAPIRO: There's a new analysis of Helene and how climate change contributed to the strength of that hurricane. It's just come out. Tell us what it says.

WALDHOLZ: Basically, the study found that climate change made Helene stronger, it dropped significantly more rain and it was just more likely because of human-caused warming. And a lot of that is down to these warmer water temperatures. The analysis found that climate change made those current temperatures in the Gulf of Mexico way more likely, something like 200 to 500 times more likely.

SHAPIRO: Wow. So we're talking about higher storm surge, more rain, more powerful winds - all of which has a real impact on the life and well-being of humans who are in the storm's path. Is there anything that can be done about this? What does this mean for people facing natural disasters?

WALDHOLZ: Yeah, so, I mean, right now, everyone in the path should be paying attention to local officials, listening to evacuation orders. And I'd really stress that that's true for people who aren't on the coast as well. We just saw Helene cause some of the worst damage really far inland with flash flooding, and so the wind and the storm surge are not the only threats from these hurricanes. Heavy rain and flooding are also a big risk. So just urge everyone who is anywhere near the path of the storm to be paying attention to local warnings. But in the long term, you know, the U.S. needs to prepare to see more storms like this as long as warming continues. And ultimately, the only way to head off that trend of worse and worse storm is to limit global warming. And that ultimately means burning less fossil fuels.

SHAPIRO: But am I correct that the intensity of the storms we're seeing now is a reflection of fossil fuels that were released decades ago, and so even if we stopped emitting carbon today, we would have to prepare for a future of more extreme weather events?

WALDHOLZ: Yes, we should be preparing now to see more storms like Helene and Milton. The kinds of storms that were really rare in the past just aren't going to be that rare anymore.

SHAPIRO: That's NPR's Rachel Waldholz. Thank you.

WALDHOLZ: Thanks, Ari. Transcript provided by NPR, Copyright NPR.

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