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Global warming slowdown answer lies in depths of Atlantic, study finds

 

Oceans

Scientists believe excess heat is being stored in the Atlantic and Southern Oceans, not the Pacific Ocean. Photograph: Peter Barritt / Alamy/Alamy

 

Powered by Guardian.co.ukThis article titled “Global warming slowdown answer lies in depths of Atlantic, study finds” was written by Adam Vaughan, for The Guardian on Thursday 21st August 2014 20.35 UTC

The key to the slowdown in global warming in recent years could lie in the depths of the Atlantic and Southern Oceans where excess heat is being stored – not the Pacific Ocean as has previously been suggested, according to new research.

But the finding suggests that a naturally occurring ocean cycle burying the heat will flip in around 15 years’ time, causing global temperature rises to accelerate again.

The slowdown of average surface temperature rises in the last 15 years after decades of rapid warming has been seized on by climate change sceptics and has puzzled scientists, who have hypothesised that everything from volcanic eruptions and sulphur from Chinese power stations to heat being trapped deep in the oceans could be the cause. Several studies have focused on the Pacific as potentially playing a major role.

The new study, published in the journal Science on Thursday, concludes that the Pacific alone cannot explain the warming “hiatus” and that much of the heat being trapped by greenhouse gases at record levels in the atmosphere is being sunk hundreds of metres down in the Atlantic and Southern Oceans.

Ka-Kit Tung, author of the paper and University of Washington professor, said: “The finding is a surprise, since the current theories had pointed to the Pacific Ocean as the culprit for hiding heat. But the data are quite convincing and they show otherwise.”

“We are not downplaying the role of the Pacific. They are both going on [the oceans having an effect on temperatures]; one is short term [the Pacific], one is long term [the Atlantic],” he told the Guardian.

A shift in the salinity of the north Atlantic triggered the effect around the turn of the century, the study says, as surface water there became saltier and more dense, sinking and taking surface heat down to depths of more than 300 metres.

Using temperature data from floats across the world, Tung found the Atlantic and Southern Oceans “each account for just under half the global energy storage change since 1999 at below 300m”. The study’s result, he says, does not support the “Pacific-centric” view of earlier work on whether heat is being stored.

“We were surprised to see the evidence presented so clearly. When you go with the energy, you cannot argue with that,” said Tung.

Global Temperatures and CO2

Global temperature rise and CO2. Photograph: /Guardian

Jon Robson, a climate scientist at the University of Reading and who is unconnected to the study, said the new work did not disprove evidence of the Pacific’s role in the warming slowdown.

 

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