Rising temperatures, increased acidification, declining oxygen levels, and decreased food supplies could affect 55% of the world’s oceans by 2030, 86% by 2050, with the fragile Arctic region taking a particularly heavy hit, according to a paper published last week in the journal Nature Communications.
Even in a more “moderate” scenario that factors in carbon reduction commitments under the Paris Agreement, “large swaths of the ocean will be altered by climate change,” the Washington Post reports. “But the researchers found that cutting greenhouse gas emissions could significantly delay future changes, giving marine organisms more time to migrate or adapt.”
The study concludes that the world’s oceans are warming 13% faster than researchers previously believed, The Guardian reports.
Lead author Stephanie Henson of the University of Southampton’s National Oceanography Centre said variability is a regular fact of life for ocean organisms. “It gets warm in the summer and it gets cold in the winter, and species survive that kind of range in temperature or other conditions perfectly well,” she told the Post.
But faced with hotter temperatures, lower pH, and less oxygen than nature has ever produced, “some organisms may no longer be able to tolerate the changed conditions and will be forced to migrate, evolve as a species, or face possible extinction,” the Post notes.
Under a “business as usual” scenario, with no action to curb greenhouse gas emissions, an “alarming portion of the ocean” would face multiple, simultaneous changes, writes Post correspondent Chelsea Harvey. “We think that multiple different factors occurring at the same time probably have different responses in the marine environment than just one factor at a time,” Henson said. “So, for example, the combination of warming and ocean acidification may be even more detrimental than just one of those factors alone.”
The study models showed climate change mitigation slowing down those effects by about 20 years. “Mitigation doesn’t stop the emergence of multiple different stressors in the ocean, but it does slow things down quite significantly,” Henson said. And that delay “could buy time for organisms to move or adapt to their surroundings,” Harvey notes, at least in some ecosystems.
Meanwhile, the U.S. National Oceanic and Atmospheric Administration—now facing deep budget cuts courtesy of the Trump White House—reported Friday in the journal Science Advances that the rate of ocean warming has almost doubled in the last 24 years compared to the previous three decades.
“The findings are important because the world’s oceans provide one of the best records of the excess energy trapped on Earth by increased greenhouse gases, largely from the burning of fossil fuels,” InsideClimate News reports. “As the seas heat up from climate change, the water expands and rises, causing coastal flooding and, in Antarctica, ice shelves to disintegrate.”
The study attributes up to 50% of sea level rise—much more than the 30 to 40% in models produced by the Intergovernmental Panel on Climate Change—to ocean warming.
“This directly affects our understanding of sea level,” said climate scientist Kevin Trenberth of the U.S. National Center for Atmospheric Research. “And the regional information is critical for climate forecasts and understanding future global warming impacts.”