Oceans are getting warmer, more acidic and rising, which in turn weakens fish stocks and harms coastal communities, a new international report has found. Climate change is also supercharging tropical storms and hurricanes, according to the report, directly threatening hundreds of millions people around the globe.
Yesterday, the Intergovernmental Panel on Climate Change—the United Nations-chartered body studying global warming—released a special report on the ocean and cryosphere, or the frozen parts of Earth. The study is a massive undertaking with 100 authors from 36 nations, citing about 7,000 scientific papers. The findings, especially for the oceans, are overwhelming.
Earth’s oceans have acted as a climate change buffer for the last few decades, reports Brad Plumer at the New York Times. The churning waters have absorbed about 20 to 30 percent of the carbon dioxide emissions produced by humanity, and they have also absorbed about 90 percent of the excess heat trapped in the atmosphere by greenhouse gases. But that has come at a cost.
The ocean has started warming up with marine heatwaves doubling in frequency since 1982. These heatwaves have increased in intensity, having major effects on sensitive ecosystems like coral reefs. If temperatures are allowed to reach 2 degrees Celsius above preindustrial levels, heatwaves will be 20 times more frequent and 50 times more frequent if emissions are allowed to continue climbing even higher, the study concludes.
The chemistry of the oceans is also changing. Warming prevents different layers of ocean from mixing, which in turns decreases oxygen levels and nutrient exchange. All that CO2 is making the water more acidic, which interferes with the life cycles of different organisms, like how oysters make their shells. Over the next few decades, the report concludes, “the ocean is projected to transition to unprecedented conditions.”
All of that is already reshaping habitats across the ocean, with fish abundance and distribution changing. Add those changes to other major ocean problems, like overfishing and pollution, and the scenario is dire.
“The oceans are sending us so many warning signals that we need to get emissions under control," as the report’s lead author Hans-Otto Pörtner, a climatologist at the Alfred Wegener Institute in Germany, tells the New York Times. “Ecosystems are changing, food webs are changing, fish stocks are changing, and this turmoil is affecting humans.”
The cryosphere is in equally rough shape. In Arctic regions, it’s expected that 25 percent of near surface permafrost, or soils that are frozen year round, will thaw by 2100, even if temperature increases are held under 2 degrees Celsius. If emissions continue to increase, up to 70 percent of the near-surface permafrost could thaw. That could speed up climate change, since thawing permafrost has the potential to release massive amounts of carbon into the atmosphere. While emerging plants would sequester some of the CO2 release, it’s unlikely they could keep up the rate of the thaw.
All these changes in the water and ice are already being felt by many people—and soon others will feel it, too. Melting permafrost and rising ocean levels are forcing people near the Arctic to relocate villages. Smaller glaciers in mountainous regions of Europe, east Africa, Indonesia and the tropical Andes are expected to lose 80 percent of their ice by 2100. Likewise, avalanches, rock falls and loss of water resources threaten 670 million people living in mountain regions.
Even more, the loss of ice and snow in the mountains threatens agriculture and hydropower in the regions down below. Just yesterday, authorities warned that the massive Planpincieux glacier on the south side of the Mont Blanc massif in the Alps is beginning to collapse, and 8.8 million cubic foot section of the ice is expected to crumble into the valley near the popular hiking town of Courmayeur.
Accelerating sea level rise is threatening coastal communities and low-lying islands. Even with emissions reductions, sea level is expected to rise by one to two feet by 2100. If emissions are allowed to increase, the rise is estimated to be from 2 to 4.75 feet in the same period.
The amount of fish is expected to decrease by a quarter by the end of the century as well, imperiling food security throughout the world and affecting the livelihoods of fishing communities, even in developed nations. “If the fish leave, that affects the small fishing fleets we have up and down the California coast,” as Gretchen Hofmann, a marine biologist at the University of California, Santa Barbara who was not involved in the study, tells Plumer. “So there’s the risk of real economic and social problems.”
According to a press release, the solution to slowing the impacts to the ice and water is familiar to everyone by now: reduce carbon emissions as greatly and as soon as possible.
“The more decisively and the earlier we act, the more able we will be to address unavoidable changes, manage risks, improve our lives and achieve sustainability for ecosystems and people around the world–today and in the future,” says Debra Roberts, co-chair of the IPCC Working Group II.
Robinson Meyer at The Atlantic reports that this is the last of three special reports put out by the IPCC in the last year, including a report last October detailing the impacts of a 1.5 degree Celsius temperature increase and another report with equally sobering report on the impact of climate change on land released last month.