Atlantic Ocean soaks up heat to slow global warming, scientists believe

Experts explain hiatus in climate change by showing ocean soaks up vast amounts of heat

PUBLISHED : Friday, 22 August, 2014, 11:22pm
UPDATED : Saturday, 23 August, 2014, 1:28am

The Atlantic Ocean is masking global warming this century by soaking up vast amounts of heat from the atmosphere in a shift likely to reverse from around 2030 and spur fast temperature rises, scientists say.

The theory is the latest explanation for a slowdown in the pace of warming at the earth's surface since about 1998 that has puzzled science because it conflicts with rising greenhouse gas emissions, especially from emerging economies led by China and India.

"We're pointing to the Atlantic as the driver of the hiatus," said Ka-kit Tung, of the University of Washington in Seattle and a co-author of the study published in the journal Science.

The study said an Atlantic current carrying water north from the tropics sped up this century and sucked more warm surface waters down to 1,500 metres, part of a natural shift for the ocean that typically lasts about three decades.

It said a return to a warmer period, releasing more heat stored in the ocean, was likely from 2030. When it does, "another episode of accelerated global warming should ensue", the authors wrote.

Almost 200 governments aim to agree on a deal to combat climate change at a summit in Paris late next year, and the hiatus has heartened sceptics who doubt there is an urgent need for an immensely expensive shift from fossil fuels to renewable energies.

Several previous studies have suggested that the larger Pacific Ocean was the likely site of the "missing heat" from man-made greenhouse gases, perhaps linked to a series of La Nina cooling events in the Pacific in recent years.

Other suggestions for the slowdown in warming have included a rise in industrial pollution that is blocking sunlight.

A separate team of scientists writing in the journal Nature Geoscience on Sunday said that factors including swings in the sun's output and sun-blocking dust from volcanic eruptions may account for gaps in understanding the warming trends.

In addition, La Nina cooling events in the Pacific Ocean had played a role, according to the report that examined why computer models of the climate had over-estimated temperature rises in the past decade.

"It will be interesting to see how and if these ideas are connected" with the theory of the Atlantic, lead author Markus Huber said of the study by the Institute for Atmospheric and Climate Science in Zurich.

The Atlantic theory suggested a shift in salinity may have caused more heat to be transferred to the depths. Even though global warming has slowed, 13 of the 14 warmest years on record have been this century, according to UN estimates.

A UN panel says it is at least 95 per cent certain that human-related emissions, rather than natural variations in the global climate, are the main cause of rising temperatures since 1960 that have caused more heatwaves, massive rain events and rising sea levels.