Surprising new research reveals strong heat build-up in the oceans, suggesting a faster rate of global warming

The world's oceans have absorbed much more excess heat in recent decades than scientists thought, suggesting the Earth could heat up faster than expected in the coming years, according to a new study released Wednesday.

Over the last 25 years, the world's oceans have conserved 60% more heat each year compared to scientists, said Laure Resplandy, a geoscientist at Princeton University, who led the groundbreaking study released on Wednesday. the journal Nature. The difference is a huge amount of extra energy, coming from the sun and trapped by the Earth's atmosphere – more than eight times the world's energy consumption, year after year.

On the scientific side, the new discoveries help resolve persistent doubts about the rate of ocean warming before 2007, when reliable measurements from devices called "Argo floats" were implemented around the world. . Previously, different types of temperature recordings – and their general absence – contributed to obscuring the speed with which the oceans warmed.

The higher than expected amount of heat in the oceans means that more heat is retained each year in the Earth's climate system, instead of escaping into space. Essentially, more heat in the oceans indicates that global warming is more advanced than scientists thought.

"We thought we were not warming the ocean and the atmosphere too much because of the amount of CO2 emitted," said Resplandy, who has published work with experts from the Scripps Institution of Oceanography and several other institutions from the United States, China, France and Germany. "But we were wrong. The planet has warmed more than we thought. It was hidden from us simply because we did not sample it well. But it was there. It was already in the ocean.

Wednesday's study could also have important political implications. If ocean temperatures rise faster than expected, this could leave even less time for nations to significantly reduce global carbon dioxide emissions, in the hope of limiting global warming to the ambitious goal of 1.5 ° Celsius (2.7 degrees Fahrenheit) above pre-industrial levels. .

The world has already warmed by 1 degree Celsius since the end of the 19th century. UN-backed scientists have reported this month that as global warming continues to rise, the world faces a daunting challenge in trying to limit this warming to another half-degree Celsius. The group noted that "unprecedented" action from world leaders is needed over the next decade to achieve this goal.

Meanwhile, the Trump administration has continued to lower regulations aimed at reducing carbon emissions from vehicles, coal-fired power plants and other sources, and has announced plans to withdraw from the company. Paris agreement on climate. In one case, the administration relied on the assumption that the planet would warm up by the end of the century a disastrous climate at 7 degrees Fahrenheit, about 4 degrees Celsius, saying that a proposal to soften vehicle fuel efficiency standards would have only a minor climate. impacts.

The new research highlights the potential consequences of global inaction. The rapid warming of the oceans means that the seas will rise more quickly and more heat will be delivered to critical places already suffering the effects of global warming, such as coral reefs in the tropics and the Greenland ice sheets and the Atlantic Ocean. 39; Antarctica.

"If the estimate of heat absorption by the oceans was wider, adaptation and mitigation of our changing climate would become more urgent," said Pieter Tans, group leader. NOAA carbon cycle greenhouse gases, involved in the study.

The oceans absorb more than 90% of the excess energy trapped in the planet's atmosphere.

The new research does not directly measure the temperature of the ocean. It rather measures the volume of gas, especially oxygen and carbon dioxide, that have escaped from the ocean in recent decades and have been heading towards the warming atmosphere. The method provided scientists with a reliable indicator of ocean temperature change as it reflected the fundamental behavior of a heated fluid.

"When the ocean heats up, it loses some gas in the atmosphere," Resplandy said. "It's an analogy that I do all the time: if you leave your Coca-Cola in the sun, it will lose gas."

This approach allowed researchers to recheck the contested history of ocean temperature in a different and innovative way. In doing so, they calculated a higher figure for ocean warming over time.

"I have the impression that it is a triumph of earth system science. The fact that we can have confirmation of the heat content of the oceans of atmospheric gases is extraordinary, "said Joellen Russell, professor and oceanographer at the University of Arizona. "You have the team here on this paper."

But Russell said the results themselves are hardly as edifying.

"This has implications for climate sensitivity, that is, that a certain amount of CO2 is heating us up," said Russell, adding that the world could have a "carbon budget." "lower than the one we thought. This budget refers to the amount of carbon dioxide that humans can emit while continuing to heat below dangerous levels.

Scientists have calculated that due to the increase in heat already stored in the ocean, the maximum emissions that the world could produce while avoiding a warming of 2 degrees Celsius (3.6 Fahrenheit ) should be reduced by 25%. This represents a very significant reduction of a "carbon budget" already very narrow.

The group of climate scientists from the United States recently said that global carbon emissions should be halved by 2030 if the world hopes to stay below 1.5 ° C of global warming. But Resplandy said that evidence of a faster warming of the ocean "alters the probability, making it more difficult to stay below the 1.5 degree temperature target.

Understanding what is happening with the Earth's oceans is essential simply because they are much more than the atmosphere the mirror of ongoing climate change.

According to a major climate report released last year by the US government, the world's oceans have absorbed about 93 percent of the excess heat generated by greenhouse gases since the mid-twentieth century. Scientists have found that ocean heat has increased at all depths since the 1960s, while surface water is warming as well. The federal climate report predicted an overall increase in average sea-surface temperature to nearly 5 degrees Fahrenheit by 2100 if emissions continued unabated, with even higher levels of warming in some regions US coastal areas.

The world's oceans currently absorb more than a quarter of the carbon dioxide emitted each year by human activities, making them more acidic and threatening fragile ecosystems, according to federal researchers. "The rate of acidification is unprecedented for at least 66 million years," says the government's climate report.

Paul Durack, a researcher at Lawrence Livermore National Laboratory in California, said Wednesday's study offers "a very interesting new idea" but is "quite alarming".

The warming found in the study is "more than twice the estimates of long-term warming from the '60s and' 70s to the present," said Durack, adding that if these rates were validated by others studies, "that would mean the rate of warming and the sensitivity of the Earth's system to greenhouse gases is the upper limit." He said that if scientists underestimated the amount of heat absorbed by the oceans, "that would mean that we will have to go back to the drawing board "on the aggressiveness of the mitigation measures that the world must take quickly to limit future warming.

Beyond the longer-term consequences of warmer oceans, Russell added that in the short term, even small changes in ocean temperatures can affect weather conditions in specific locations. For example, scientists have said that warmer oceans off the coast of New England have helped intensify winter storms.

"We have just discovered how important ocean warming is for our daily lives, for our daily climate," she said.