The Oceans Absorbed An Unfathomable Amount Of Heat This Decade

Without the oceans, we'd really be screwed.

That's because the sprawling seas — some  321,003,000 cubic miles of them — soak up over 90 percent of the heat trapped on Earth by human-created carbon emissions, which are still growing. This colossal heat absorption tempers the continued atmospheric warming of the remote, pale blue dot we inhabit.

"The ocean is delaying our punishment," said Josh Willis, an oceanographer at NASA's Jet Propulsion Laboratory. 

The quantity of heat the oceans have absorbed in the last decade is difficult to describe, if not imagine. The ocean's heat content is measured in the most standard unit of energy, joules (using a 100-watt lightbulb for three hours eats up 1,080,000 joules). Between 2010 and 2019, the seas absorbed roughly 110,000,000,000,000,000,000,000 joules of energy. 

To help grasp this outrageous number, we'll need something big, so I've converted the ocean's heat content into nuclear bomb explosions. Specifically, explosions of the most powerful nuclear bomb ever detonated, the Tsar Bomba. In a grandiose test, the Soviets dropped this 59,525 pound, blimp-shaped behemoth in October 1961, which released some 50 megatons of energy (that's the energy produced by exploding 50 million tons of dynamite).

The conclusion: The ocean has absorbed (roughly) the equivalent amount of energy released when detonating a Tsar Bomba once every 10 minutes for 10 years. 

(For reference, the atomic bomb the U.S. dropped on Hiroshima on August 6, 1945 had the explosive force of 15,000 tons of TNT — so the Tsar Bomba detonation was over 3,000 times more powerful.)

Yes, that's a ridiculous amount of energy. But the ocean is a ridiculously effective sponge. "The ocean is the largest reservoir of heat in the climate system," noted Matthew Long, an oceanographer at the National Center for Atmospheric Research.

"Water can store heat better than pretty much any other substance in the universe," added Willis.

"The ocean is delaying our punishment."

Since the Industrial Revolution, the upper ocean layers have absorbed enough heat to warm up on average by a little over 1 degree Celsius (1.8 degrees Fahrenheit), said Willis. This warming will continue, likely through much of the century, at least. 

That's because carbon levels in Earth's atmosphere are the highest they've been in at least 800,000 years — though more likely millions of years. Civilization's carbon emissions must fall to zero for Earth to even start cooling down. That's an unparalleled challenge.

Already, humanity's warming of the oceans has driven significant, adverse disruptions of the seas.

"We're changing the basic metabolic state of the largest ecosystem on the planet," said Long. "We’re rapidly pushing it out of whack."

Of note, higher water temperatures mean a reduction in the amount of oxygen dissolved in the ocean — which sea life relies on to breathe and see. Higher temperatures mean water generally holds less oxygen and other gases. What's more, the surface waters (which are next to the air and absorb oxygen) continue to soak up bounties of heat, creating a robust, warm layer of water atop the sea. This layer of excessively warmed, buoyant water is more resistant to mixing in with the layers below, which deprives deeper dwelling animals of oxygen. 

"Deoxygenation of the open ocean is one of the major manifestations of global change," notes a new International Union for Conservation of Nature report on ocean deoxygenation. 

Even if civilization finds a way to limit Earth's warming this century to just 1.5 C (2.7F) above pre-industrial revolution temperatures — now a near impossible feat — the oceans will still warm and continue losing oxygen this century, the report concludes.

But, critically, less atmospheric warming means less ocean warming. Society might very well miss the ambitious 1.5 C or 2 C goals set forth by the U.N., but slashing emissions and perhaps getting somewhere near these warming targets is still possible — even if the U.S. has candidly surrendered its climate leadership and effectively left (for now) the international effort to cut emissions.

"We have to start turning the ship around now to meet those targets," said Long. 

The ship has yet to turn around.