NOEL KING, HOST:
The U.N. has released a new climate science report on oceans. Here's are the headlines. Ice is melting everywhere and sea level rise is accelerating. The oceans are getting hotter faster. This is killing sea animals and disrupting fisheries. And there's also a relatively new problem - heat waves in the oceans.
NPR's Rebecca Hersher has the story.
REBECCA HERSHER, BYLINE: The report is a synthesis of everything we know about climate change in the oceans so everyone's on the same page about what's happening. And what's happening, in the most basic terms, is that the oceans are getting a lot hotter. The rate of ocean warming has doubled since 1993. And marine heat waves are getting more frequent and intense. Haven't heard of marine heat waves? That's because they're new.
Andrew Pershing is the chief scientific officer at the Gulf of Maine Research Institute.
ANDREW PERSHING: It's sort of remarkable that prior to 2012, 2013, nobody kind of thought about heat waves in the ocean. And then in 2012, we had a huge event here in the Northwest Atlantic. And the Gulf of Maine was right at the center of it.
HERSHER: Just like a heat wave on land, the water near Maine got abnormally hot that year. Scientists had never seen anything like it. And it was happening in other places, too.
PERSHING: It was a real surprise. And then subsequently, these kind of heat wave events have popped up all over the ocean. So we've actually had three major heat waves in the Gulf of Maine - 2012, 2016 and 2018 - and repeat heat waves in the North Pacific. Australia's had some repeat heat waves. So it's really becoming a part of the conversation in oceanography.
HERSHER: Because they're so new, scientists still aren't able to predict ocean heat waves or say much about how long they'll last once they start. In fact, right now, there's a marine heat wave off the west coast of the U.S. where there's an area of abnormally hot water known as the blob.
HILLARY SCANNELL: How hot is it? So right now, it is up to 4 degrees Celsius above what we would normally expect.
HERSHER: Hillary Scannell studies marine heat waves at the University of Washington. Four degrees Celsius is about 7 degrees Fahrenheit hotter than usual - a big enough difference where you'd notice it if you touched the water.
SCANNELL: This patch of warm water is very unusual because it is so extreme and intense.
HERSHER: Which is bad news for the animals that live in that water. Noah Oppenheim is the executive director of the Pacific Coast Federation of Fishermen's Associations. He's also a former marine researcher.
NOAH OPPENHEIM: The impacts to the ocean sort of cascade up through the food web starting with plankton and into the krill, which form the prey base for animals as small as sardines all the way up to salmon and then whales.
HERSHER: That cascade comes up in the new report. As oceans get hotter and marine heat waves get more intense, it knocks everything in the ocean out of equilibrium. That's already happened in the Pacific Northwest in recent years. Blobs of hot water there caused blooms of toxic algae, which meant the region's Dungeness crab fishery was closed for months. Salmon was also decimated.
The federal government declared fishery disasters in 2016 and 2017. It's one of the many economic challenges that come with warmer oceans in addition to the costs of dealing with sea level rise. And hotter oceans also affect the weather far from the coasts, contributing to droughts and driving bigger, wetter storms. Cutting greenhouse gas emissions dramatically will help with all of these effects but slowly.
OPPENHEIM: Even if we cut carbon emissions right now, we are still looking at 20 or 30 years of change. And so that means no matter what we do, we have to figure out how are we going to adapt to these changes?
HERSHER: Which will mean remaking the global economy, rebuilding infrastructure and rethinking how we manage coastal communities.
Rebecca Hersher, NPR News.
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