The world’s oceans are getting warmer and rising faster than thought – melting even more ice and snow – while also losing oxygen and becoming increasingly acidic, says an updated report from the United Nations’ climate arm out Wednesday.
It’s a report that outside scientists called grim without aggressive action, and, in some cases, findings that are still too conservative.
“The oceans and the icy parts of the world are in big trouble and that means we’re all in big trouble too,” said one of the report’s lead authors, Michael Oppenheimer, professor of geosciences and international affairs at Princeton University. “The changes are accelerating.”
The UN Intergovernmental Panel on Climate Change’s special report on the Ocean and Cryosphere in a Changing Climate is the third in a reporting series, following the “1.5°” report in October 2018 and the lands report in August 2019.
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The oceans absorb more than 90% of the excess heat from carbon pollution in the air, as well as much of the carbon dioxide itself. The seas warm more slowly than the air but trap the heat longer with bigger side effects – and the report links these waters with Earth’s snow and ice, called the cryosphere, because their futures are interconnected.
For the first time, the international team of scientists behind the report are projecting that some island nations are likely to become uninhabitable due to climate-related ocean and cryosphere change.
But many of the worst-case projections in the report can still be avoided depending on how the world handles the emissions of heat-trapping gases, the report said.
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The IPCC increased its projected end-of-century sea level rise in the worst-case scenario by nearly four inches (10 centimeters) from its 2013 projections because of the increased recent melting of ice sheets in Greenland and Antarctica.
The new report projects that, under a business-as-usual scenario for carbon emissions, seas by the end of the century will rise between two feet (61 centimeters) and 43 inches (110 centimeters) with a most likely amount of 33 inches (84 centimeters). This is slightly less than the traditional 1 meter (39 inches) that scientists often use.
“It’s really from the highest mountains to the oceans, the systems are directly linked to each other,” said Regine Hock, an author on this report and a professor of geophysics at the University of Alaska. “It is very important to recognize that you cannot just go and consider one system or one in isolation, but it’s all these changes happening consistently and coherently around the world and they’re linked together.”
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Food security, for one, can be greatly impacted by changing oceans.
“This IPCC report is significant because it shows clearly that we cannot afford to leave oceans – and in particular, fisheries – out of the climate change discussion. Inevitable climate change impacts on the ocean mean inevitable impacts on the integrity of ocean ecosystems and the global nutrition, food security and livelihoods of hundreds of millions of people around the world,” said Doug Rader, chief oceans scientist for the Environmental Defense Fund.
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Here are some of the key takeaways:
-Oceans have gotten warmer, more acidic, and are losing oxygen, resulting in a cascade of negative effects that wreak havoc on marine ecosystems, threaten the collapse of the world’s fisheries, and turbocharge deadly hurricanes and tropical storms.
-Polar ice sheet loss has increased dramatically, overtaking thermal expansion and glacial melt as the predominant cause of sea level rise since the IPCC last made an assessment in 2013. Sea level rise is now accelerating and the IPCC is now forecasting higher sea levels under the high-emissions pathway. Even under a low-emissions scenario, most of the East and West Coasts of the U.S. will experience a hundred-year flood every year unless major investments are made to adapt to these coming extreme events. Globally, this investment would run up to hundreds of billions of dollars per year.
-The world has reached or is nearing critical tipping points. Polar ice sheets may now be unstable, and as a result long-term melting may now be irreversible. Meanwhile, methane and carbon released as permafrost thaws will further contribute to warming, pushing toward a tipping point that, if passed, could trap the planet in a vicious feedback loop that could unleash accelerating warming.
-Water scarcity and wildfires will become worse as glaciers melt and snowpack declines. Already, communities that rely on glacial melt and snow runoff for agriculture and drinking water are left high and dry, while wildfires have grown increasingly common in the Arctic and high mountains as permafrost and snowpack melt.
The Associated Press contributed to this report.