Washington: Deeper regions of the Pacific Ocean are warming 15 times faster than they did during the previous 10,000 years, a new study has found.
A recent slowdown in global warming has led some sceptics to renew their claims that industrial carbon emissions are not causing a century-long rise in Earth`s surface temperatures.
The study adds support to the idea that the oceans are absorbing some of the excess heat, at least for the moment.
In a reconstruction of Pacific Ocean temperatures in the last 10,000 years, researchers have found that its middle depths have warmed 15 times faster in the last 60 years than they did during apparent natural warming cycles in the previous 10,000.
"We`re experimenting by putting all this heat in the ocean without quite knowing how it`s going to come back out and affect climate," said study coauthor Braddock Linsley, from Columbia University`s Lamont-Doherty Earth Observatory.
"It`s not so much the magnitude of the change, but the rate of change," said Linsley.
The findings suggest that the oceans may be storing even more of the effects of human emissions than scientists have so far realised.
"We may have underestimated the efficiency of the oceans as a storehouse for heat and energy," said study lead author, Yair Rosenthal, a climate scientist at Rutgers University.
"It may buy us some time how much time, I don`t really know. But it`s not going to stop climate change," said Rosenthal.
Ocean heat is typically measured from buoys dispersed throughout the ocean, and with instruments lowered from ships, with reliable records at least in some places going back to the 1960s.
To look back farther in time, scientists have developed ways to analyse the chemistry of ancient marine life to reconstruct the climates in which they lived.
In a 2003 expedition to Indonesia, the researchers collected cores of sediment from the seas where water from the Pacific flows into the Indian Ocean.
By measuring the levels of magnesium to calcium in the shells of Hyalinea balthica, a one-celled organism buried in those sediments, the researchers estimated the temperature of the middle-depth waters where H Balthica lived, from about 1,500 to 3,000 feet down.
The temperature record there reflects middle-depth temperatures throughout the western Pacific, the researchers say, since the waters around Indonesia originate from the mid-depths of the North and South Pacific.
The study was published in the journal Science.