2018 was the ocean's hottest year. We'll feel it a long time.

Earth’s oceans are warmer now than at any point since humans started systematically tracking their temperatures, according to research published on January 16 in Advances in Atmospheric Sciences. The oceans have sopped up more than 90 percent of the heat trapped by human-emitted greenhouse gases, slowing the warming of the atmosphere—but causing many other unwelcome changes to the planet’s climate.

Even a slightly warmer ocean can have dramatic impacts. Other new research shows that warmer oceans make waves stronger. Warmer waters fuel stronger storms, increasing the damage that hurricanes and tropical storms inflict. The added warmth hurts coral habitats and stresses fisheries. Around Antarctica, yet another new study suggests, ice is melting about six times faster than it was in the 1980s—an increase due in part to the warmer waters lapping at the continent’s edge.

“The oceans are the best thermometer we have for the planet,” says Zeke Hausfather, an energy and climate scientist at the University of California, Berkeley, who used the ocean heat data published today in an analysis published last week in Science. “We can really see global warming loud and clear in the ocean record.”

Missing heat is now found

As early as the 1800s, scientists suspected that adding carbon dioxide to the atmosphere would cause air temperatures around the planet to rise. By the 1960s, once they started keeping careful track of both air temperatures and carbon dioxide levels around the world, their predictions were borne out.

The atmosphere didn’t seem to be warming quite as much as model calculations indicated it should, however. Where could the extra heat be going?

Some oceanographers suspected that the “missing” heat was being absorbed into the oceans—but measuring that heat was much harder than measuring air temperatures. Although research ships crossing the ocean would occasionally dip a probe into the water to test the temperature, those data were tiny blips in the wide expanse of the sea.

So scientists pulled together all data they could find, from observations from commercial ships to naval data to historical records. And when all that was compiled, the scientists realized that the oceans were, in fact, acting as an enormous buffer for the climate system, like a giant pillow softening the hard landing of climate change.

In the last decade, measurements of the ocean's heat content have been improved dramatically by a new tool: Some 3,000 autonomous sensors, called Argo floats, have been scattered around the ocean. They regularly record temperatures in the top 6,500 feet of the water column and have immensely improved the quality of the data scientists have to work with for these estimates.

Thanks to those measurements, it's now clear that the oceans are absorbing some 90 percent of the heat our carbon emissions have trapped in the atmosphere—the most recent estimate, published last week, pegs that number at 93 percent. If all the heat the ocean absorbed from 1955 onward were suddenly added to the atmosphere, air temperatures would rocket by more than 60 degrees.

In other words, the oceans are acting as a giant thermal buffer, protecting us from feeling all the heat of climate change directly. But the heat isn't going away.

To continue reading: https://www.nationalgeographic.com/environment/2019/01/oceans-warming-faster-than-ever/