Even if you hate the beach, live inland and aren’t bothered by dwindling fisheries, the latest rise in ocean temperatures matters to you. The ocean is like a giant closet where we are able to store 90% of the excess heat trapped by greenhouse gases. That closet is full now. The latest readings from more than 4,000 buoys around the world show record-breaking sea surface temperatures from January to March this year.
And we are on the cusp of an El Niño event—a change in wind patterns and ocean currents that opens the closet door and allows heat and energy to escape into our atmosphere. And the heat buried in the ocean comes back to haunt us.
The change in sea surface temperatures doesn’t seem to be much—they’re about 0.2°C above normal right now. But this sounds like a lot when expressed as energy that is added to the system that includes our oceans and atmosphere – 40 zetajoules, or sexillion joules. It is equal to crores of atomic bombs. This is the energy that gets trapped in the system by increasing concentrations of greenhouse gases.
That energy can manifest as heat waves or storms, according to Kenneth Trenberth, a climatologist I met a few years ago at a meeting at Princeton on the El Niño phenomenon. He was then at the National Center for Atmospheric Research in Colorado, and is now an honorary academic at the University of Auckland.
While the latest news has focused on new surface measurements, he said, the warming goes deeper. Last year he co-authored a paper that showed the ocean is warming up to 2,000 metres.
The heat doesn’t stay there because of the alternating pattern of wind and currents known as El Niño and its opposite counterpart, La Niña.
La Nina has prevailed during the last three years. During this phase, Trenberth said, trade winds push warm equatorial water from the Americas westward into the Pacific, where it gets piled up by Indonesia. Every two to seven years it turns into an El Niño pattern. The easterly winds subside so that the warm water can slide back towards the Americas.
Kim Cobb, an oceanographer and climatologist at Brown University, said El Niño events can be gentle or fierce, depending on whether strong winds begin to help warm water drift into the Pacific. . But the big ones happen every 10 to 15 years. He said that the actual purchases have taken place in 1972-73, 1982-83, 1997-98 and 2015-16. While El Niño originates in the eastern Pacific, the change in the pattern redistributes heat around the planet — upsetting the entire global atmospheric circulation, she said. The cycle of El Niño and La Niña has probably been going on for millions of years, since our continents and oceans have reached their current configuration.
Now, however, with rapid overall warming, the Pacific cycle may be strengthening even further, and is already producing more extreme conditions. “When we think of what sets the thermostat of our planet, it’s really our oceans,” she explained.
Trenberth said that even during the La Niña phase we’ve seen hot spots in the Pacific that caused trouble: “This was the area that was feeding the atmospheric rivers that flowed into California and all the spectacular rain in the Southwest and Even used to produce snow in some parts of the United States.”
Even though ocean depths have greater heat capacity, water warms first at the surface, and since cold water is heavier, that can create areas of unhealthy calm, where normal circulation stops and a stagnant oxygen-depleted ocean is formed. The drops grow. That’s why scientists are observing dangerous dead zones in the Gulf of Mexico, made worse by nitrate runoff from farms.
“It affects phytoplankton, zooplankton, fish, marine mammals and seabirds,” Trenberth said. Warming oceans also cause marine heat waves, which can destroy kelp forests and meadows that provide homes for fish and marine mammals.
Trenberth likes to use the phrase “global heating” to describe what’s going on. Global ‘warming’ refers to an increase in atmospheric temperature, while global heating suggests additional energy sloshing around the entire system that is our atmosphere and oceans.
He recently found some old videotapes of his interviews, and sent a 1997 interview from the ‘McNeil/Lehrer News Hour’, where he talks about the threat of global warming. Looking at it 26 years later, one can attest that the fundamentals of its science have not changed much. But our climate certainly is.
Faye Flamm is a Bloomberg Opinion columnist covering science.
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