Oceans apart on where the world’s extra heat is going

Climate scientists clash over warming waters while seeking to explain the global warming hiatus. James Mitchell Crow reports.

The deployment of an Argo float into the ocean. The devices measure temperature and salinity from 2000 metres depth to the surface every 10 days. – CSIRO

Over the past 10 years or so the pace of global warming has slowed and climate models have struggled to explain why. But multiple strands of research now point to an explanation – the “missing” heat is in the Pacific Ocean.

And in February, in research published in Nature Climate Change, Matthew England at the University of New England proposed a mechanism for how it was happening. The Pacific was acting like a giant air-conditioner – trade winds had sped up, churning the excess atmospheric heat into the Pacific Ocean.

Now that theory has a challenger. According to new research, published in Science in August, it is primarily the Atlantic Ocean that is cooling the planet.

Ka-Kit Tung and Xianyao Chen at the University of Washington in Seattle came to their conclusion by taking the temperature of the worlds’ oceans using data from “Argo floats” – 3,600 free-floating thermometers that repeatedly dip 2,000 metres into the depths before bobbing back up to beam home their data.

Our atmosphere may have slowed its warming in the last decade but the Argo floats, first launched in 2000, show there has been no such pause to ocean warming. “We know the oceans are sucking up heat big time, all round the planet,” says England.

But Tung and Chen have taken the Argo data further.

“We found, as others have, that the total ocean heat content does not have a hiatus,” says Tung. “What is new is we found out which ocean the heat has gone into.” Tung says the data show the Atlantic is taking up the extra heat.

But for other oceanographers that interpretation pushes the Argo data too far. To use ocean temperature data to account for the hiatus you’d need to find the ocean where the heat uptake has accelerated dramatically in the last 15 years and the Argos, first launched in 2000, can’t tell you that. “This study really stretches the limits of ocean observations,” says England.

“It’s a good study, an important study, it shows the Atlantic could be contributing to the hiatus. But I still think the Pacific is the major driver here,” he adds.

In the week since the paper was published many other leading oceanographers have made the same point.

But whatever the ultimate trigger for the hiatus, both camps agree the pause is temporary and, all too soon, global air temperatures will start rocketing upwards again.

  1. http://beta.cosmosmagazine.com/earth-sciences/has-global-warming-paused
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