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Heat waves happen in the oceans, too — and they’re getting worse

A major United Nations report shows how oceans are feeling the burn from climate change

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Coral Reefs And White Death

Oceans are increasingly taking the heat from climate change, according to a major new report released today by the United Nations Intergovernmental Panel on Climate Change (IPCC). The report is arguably one of the most comprehensive assessments to date on the effects of climate change on the Earth’s oceans and frozen water. And it points to a problem scientists are growing more concerned about: marine heat waves.

There’s plenty of robust scientific evidence that shows that extreme heat events on land are getting worse as climate change accelerates. But land dwellers aren’t the only ones feeling the burn. A growing body of research is examining similar events underwater, when the seas experience periods of unusually warm temperatures.

“This is a phenomena that we should be placing higher attention on,” Ko Barrett, vice chair of the IPCC, said in a press briefing. Marine heat waves, she said, are an “emerging issue” and this is the first time that the United Nations body has dedicated so much study to it.

More than 100 scientists spanning over 30 countries contributed to the study, called the Special Report on the Ocean and Cryosphere in a Changing Climate. It was unveiled during a meeting of the intergovernmental panel in Monaco just one day after the United Nations held a special summit in New York where Secretary-General António Guterres called on countries to step up their plans to avert climate crisis. 

The frequency of heat waves in oceans has very likely doubled since 1982

The report found that the frequency of heat waves in oceans has very likely doubled since 1982. And things are probably going to get worse. By 2081, the frequency of these extreme events could jump by 20 to 50 times, depending on how successful the world is at cutting down on the greenhouse gas emissions heating our planet. In a scenario with continued high emissions, those underwater extreme heat events could become ten times more intense. 

They’re already brutal. In 2014 and 2015, a heat wave called “the Blob” appeared in the Pacific and wreaked havoc on marine ecosystems from Hawaii to Alaska. The high temperatures can kill coral reefs, strand sea lions on shore, and shut down fisheries and crabbing. And since ocean temperatures have an effect on weather systems, the blob even came after California — contributing to an epic drought in 2014 that the American Geophysical Union said was the worst in the region in 1,200 years

“I’d say this is an important area of scientific understanding that’s emerged in the last few years,” Stanford professor and senior fellow Noah Diffenbaugh, who was not involved with the IPCC report, tells The Verge. “We’re seeing an emergence of these marine heatwaves in the ocean conditions, we’re seeing an emergence of their impacts on ecosystems and communities. And we’re seeing an emergence of their remote influence on weather and climate over land.”

There’s a potentially concerning new “blob” — an area of unusually warm water marked red on maps — developing in the Pacific that the National Oceanic and Atmospheric Administration is monitoring. “It’s on a trajectory to be as strong as the prior event,” Andrew Leising, a research scientist at NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla, California, said in a statement from the agency this month. “Already, on its own, it is one of the most significant events that we’ve seen.” The agency acknowledged that previously unexpected events like the Blob are becoming more common.

“we don’t know what fires are being lit under the sea”

Even outside of these heat waves, the ocean is warming up. The report found that the rate of ocean warming has likely more than doubled since 1993. The ocean is storing more than 90 percent of the excess heat generated by human activity. “The ocean is sort of becoming the sacrificial lamb,” Francisco Chavez, senior scientist at the Monterey Bay Aquarium Research Institute, tells The Verge. He says we need to be paying much more attention to how that’s affecting life at sea. 

“We can immediately tell that there’s these enormous forest fires consuming parts of the Amazon forest, for example, but we don’t know what fires are being lit under the sea,” Chavez says. “The ocean is kind of out of sight out of mind, compared to the terrestrial systems.”

Of course, there’s more to worry about than the temperature rising, according to the IPCC report. Climate change is also contributing to oxygen loss and increased acidity in the ocean. And water woes are reaching land as the rate of sea-level rise due to ice melt and warm ocean water expanding increases.  

“The consequences for nature and humanity are sweeping and severe. This report highlights the urgency of timely, ambitious, coordinated and enduring action,” IPCC’s Barrett said. “What’s at stake is the health of ecosystems, wildlife, and importantly, the world we leave our children.”