Research uncovers buildup of ocean heat
Findings suggest faster rate of global warming
The world’s oceans have been soaking up far more excess heat in recent decades than scientists realized, suggesting that Earth could be set to warm even faster than predicted in the years ahead, according to new research published Wednesday.
Over the past quarter century, the Earth’s oceans have retained 60 percent more heat each year than scientists previously had thought, said Laure Resplandy, a geoscientist at Princeton University who led the startling study published Wednesday in the journal
Nature. The difference represents an enormous amount of additional energy, originating from the sun and trapped by Earth’s atmosphere — more than 8 times the world’s energy consumption, year after year.
In the scientific realm, the new findings help to resolve long-running doubts about the rate of the warming of the oceans prior to the year 2007, when reliable measurements from devices called “Argo floats” were put to use worldwide. Before that, different types of temperature records — and an overall lack of them— contributed to murkiness about how quickly the oceans were heating up.
The higher-than-expected amount of heat in the oceans means more heat is being retained within Earth’s climate system each year, rather than escaping into space. In essence, more heat in the oceans signals that global warming itself is more advanced than scientists thought.
“We thought that we got away with not a lot of warming in both the ocean and the atmosphere for the amount of carbon dioxide that we emitted,” said Resplandy, who published the work with experts from the Scripps Institution of Oceanography and several other institutions in the U.S., China, France and Germany. “But we were wrong. The planet warmed more than we thought. It was hidden from us just because we didn’t sample it right. But it was there. It was in the ocean already.”
The new research does not measure the ocean’s temperature directly. Rather, it measures the volume of gases, specifically oxygen and carbon dioxide, that have escaped the ocean in recent decades and headed into the atmosphere as it heats up. The method offered scientists a reliable indicator of ocean temperature change because it reflects a fundamental behavior of a liquid when heated.
“When the ocean warms, it loses some gas to the atmosphere,” Resplandy said. “That’s an analogy that I make all the time: if you leave your Coke in the sun, it will lose the gas.”
This approach allowed researchers to recheck the contested history of ocean temperatures in a different and novel way. In doing so, they came up with a higher number for how much warming the oceans have experienced over time.
“I feel like this is a triumph of earth system science. That we could get confirmation from atmospheric gases of ocean heat content is extraordinary,” said Joellen Russell, a professor and oceanographer at the University of Arizona. “You’ve got the A-team here on this paper.”
Resplandy said that the evidence of faster warming ocean “shifts the probability, making it harder to stay below the temperature target.
Understanding what’s happening with Earth’s oceans is critical simply because they, far more than the atmosphere, are the mirror of ongoing climate change.