The world’s oceans are up to 50% warmer than the Intergovernmental Panel on Climate Change estimated in its most recent report, and the rate of warming is still accelerating, a team of Chinese and U.S. scientists concludes in a study published Thursday in the journal Science.
“Observational records of ocean heat content show that ocean warming is accelerating,” said lead author Lijing Cheng of the Institute of Atmospheric Physics at the Chinese Academy of Sciences.
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“The numbers are coming in 40 to 50% [warmer] than the last IPCC report,” added co-author Kevin Trenberth, a climate scientist at the U.S. National Center for Atmospheric Research, and “2018 will be the warmest year on record in the oceans,” following record years in 2017 and 2016.
“Global warming is here, and has major consequences already,” the authors wrote in a statement. “There is no doubt, none!”
The study appeared just days after The Guardian calculated the average heat entering the world’s oceans over the last 150 years as the equivalent of 1.5 Hiroshima-size atomic bombs per second, about 1,000 times the energy use of the entire human population over the same period. The estimate was based on new research in the Proceedings of the National Academy of Sciences.
“I try not to make this type of calculation, simply because I find it worrisome,” lead author and Oxford University physicist Laure Zanne told the paper. “We usually try to compare the heating to [human] energy use, to make it less scary.” But “obviously, we are putting a lot of excess energy into the climate system and a lot of that ends up in the ocean.”
Cheng said the China-U.S. study was based in part on 13 years of measurements from a system of nearly 4,000 drifting ocean robots that “dive to a depth of 2,000 metres every few days, recording temperature and other indicators as they float back to the surface,” Thomson Reuters reports, in a story republished by CBC. “Through the data collected, scientists have documented increases in rainfall intensity and more powerful storms such as hurricanes Harvey in 2017 and Florence in 2018.”
Cheng “explained that oceans are the energy source for storms, and can fuel more powerful ones as temperatures—a measure of energy—rise.” On that basis, he predicted that storms will be more powerful statistically in the 2050-2100 period than they were between 1950 and 2000. The “delayed response” to global warming caused by the ocean’s large capacity to absorb heat means ocean warming “could be more serious in future,” he added.
“For example, even if we meet the target of the Paris Agreement, oceans will continue warming and sea levels will continue to rise. Their impacts will continue.”
“The scientists combined four data sets to paint a picture of what has been happening in the oceans since 1991,” the Washington Post states. “Trenberth and his co-authors say ocean heat content, which is a measure of the warmth of the water down to about 2,000 metres, is a ‘great metric for measuring global warming’ because the data isn’t as erratic as the temperature on land, and it captures much more of the planet.”
In conducting the study, the scientists “discovered something interesting: Their data agrees with what the climate models were predicting,” the Post notes. “‘Oh, maybe the models have more credibility than we thought,’ Trenberth said, tongue firmly in cheek.”
