ARI SHAPIRO, HOST:
Typhoon Mawar is nearing the U.S. territory of Guam. It's expected to become a Category 5 storm as it nears land, with winds of 160 miles an hour. A state of emergency is in effect for the island. NPR's Rebecca Hersher is covering this. Hey, Rebecca.
REBECCA HERSHER, BYLINE: Hi.
SHAPIRO: How dangerous is this storm for people who live on Guam?
HERSHER: It is extremely dangerous. The winds are powerful enough to snap power poles. It's pushing a wall of water in front of it. Guam is a very low-lying island, and when that storm surge arrives, it could sweep away entire homes, vegetation, trees, everything in its path. Forecasters are predicting between six and 10 feet of storm surge, and that's on the low end. There could be areas with more. That's up to the roof line of a single-story house. So it's very life-threatening. And on top of that, this storm will drop a lot of rain, up to 20 inches. So even those who live farther inland on the island will see dangerous flash flooding.
SHAPIRO: And how unusual are storms of this magnitude in this part of the world?
HERSHER: You know, they're quite rare. Guam has only experienced a couple of storms this powerful in recorded history. Part of that is just probability. You know, Guam is a very small island. So the chances that a storm will hit it are pretty low. But the other reason is that storms this powerful are really not that common, or they weren't for most of human history, but they're getting more likely because of climate change. And let me lay it out. You know, humans burn fossil fuels, release enormous amounts of carbon dioxide and other greenhouse gases into the atmosphere. Those gases trap heat. And most of that heat is actually soaked up by the world's oceans. So the oceans are heating up. And right now they're hotter than ever. This storm - it moved over abnormally warm water as it formed.
SHAPIRO: And what impact does that warm water have on the storm passing over?
HERSHER: The heat in the water - it's like the fuel for the storm. It helps the typhoon get really powerful. And that actually happened really quickly with this storm. It went from a Category 1 typhoon, which means it had winds that could barely remove a shingle from your roof when it first formed to a Category 4 typhoon. That means winds that can tear the roof off your house entirely. And all of that happened in just one day. That kind of rapid intensification - it is getting more common as the earth heats up. Now, scientists are still teasing apart that exact connection between climate change and this kind of rapid intensification. But it makes sense, right? Warmer ocean water would make that more likely because heat is power. And studies have shown a trend of more storms that are rapidly intensifying, both in the Pacific, where this storm is, and also in the Atlantic, where hurricanes form.
SHAPIRO: What other signs of climate change do you see in this particular storm?
HERSHER: There are two, and they both have to do with flooding. So climate change makes both storm surge and that inland flooding I was talking about from rain more severe. Let's take storm surge first. So storm surge from a storm like this one is more dangerous because of sea level rise. Higher seas means that there's more water on the coast, even on a sunny day. And so it makes the storm surge even more damaging when it does arrive. There's just more water.
The second connection is about rain. Torrential rain is more likely as the Earth heats up in general and also from hurricanes. And that's because a warmer atmosphere can hold more moisture. So when a storm like this one hits land, all of that water vapor - it falls as rain. And research has already shown that past storms have actually dropped more rain because of climate change. They can make that connection. That is a real possibility when this storm hits Guam in the coming hours.
SHAPIRO: Rebecca Hersher of NPR's Climate Desk. Thank you.
HERSHER: Thanks.
(SOUNDBITE OF ALEX VAUGHN SONG, "SO BE IT")
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