“Non Human Numbers”: Oceans Adding Massive Heat
January 19, 2016
A colossal amount of man-made heat has been sucked up by the world’s oceans in the past 18 years, and the rate at which that happens has been accelerating — but that’s not nearly as good as it sounds.
Scientists have long known that more than 90 per cent of the heat energy from man-made global warming goes into the world’s oceans instead of the ground. And they’ve seen ocean heat content rise in recent years. But the new study, using ocean-observing data that goes back to the British research ship Challenger in the 1870s and including high-tech modern underwater monitors and computer models, tracked how much man-made heat has been buried in the oceans in the past 150 years.
The world’s oceans absorbed approximately 150 zettajoules of energy from 1865 to 1997, and then absorbed about another 150 in the next 18 years, according to a study published Monday in the journal Nature Climate Change.
2.4 billion atomic bombs’ worth
To put that in perspective, if you exploded one atomic bomb the size of the one that dropped on Hiroshima every second for a year, the total energy released would be 2 zettajoules. So since 1997, Earth’s oceans have absorbed man-made heat energy equivalent to a Hiroshima-style bomb being exploded every second for 75 straight years (about 2.4 billion atomic bombs).
“The changes we’re talking about, they are really, really big numbers,” said study co-author Paul Durack, an oceanographer at the Lawrence Livermore National Lab in California. “They are nonhuman numbers.”
The research, published in Nature Climate Change, was led by Lawrence Livermore National Laboratory. It compared modeling results with data from a mishmash of sources, most notably from a nascent fleet of monitoring devices called deep Argo floats.
The researchers concluded that half of overall ocean warming has occurred since 1997 — a date that they noted in their paper was “nearly coincident with the beginning of the observed surface warming hiatus.”
A combination of climate pollution, a recent change in a long-running cycle of the Pacific Ocean and the current El Niño has led to a spike in warming rates recorded at the surface of the planet. That followed a surface warming slowdown; 2014 and 2015 were the warmest years on record globally.
Research groups from around the world have deployed thousands of Argo floats to measure since around the year 2000 to take temperature, salinity and other measurements. Technological advances have allowed a small fleet of deeper-diving floats to be deployed more recently. Some of those have been built to dive as deep as 20,000 feet.
“Knowing how much the ocean is warming and how fast and where are all important for knowing how much the atmosphere is going to warm and how much seas are going to rise,” said Gregory C. Johnson, a National Oceanic and Atmospheric Administration scientist who works on that agency’s Argo float program.
Monday’s paper used the new deep-sea Argo data to expand on a paper published in 2014 by Lawrence Livermore and other researchers, which revealed high levels of warming in the ocean’s surface layer.
“The oceans as an energy store are really doing a lot of the work,” said Lawrence Livermore researcher Paul Durack, who helped produce the studies that were published Monday and in 2014. “The actual temperature change is relatively small, but due to the huge heat capacity of the oceans this equates to a very, very large heat content change.”
Here, Kevin Trenberth in 2013 on Ocean Heat and climate sensitivity: