While heat pumped into and stored in the western Pacific Ocean by strengthening equatorial trade winds appears to be largely responsible for the hiatus in surface warming observed over the past 13 years, when those winds slow that heat will rapidly return to the atmosphere causing an abrupt rise in global average temperatures, scientists at Australia's ARC Center of Excellence for Climate System Science said.
"Scientists have long suspected that extra ocean heat uptake has slowed the rise of global average temperatures, but the mechanism behind the hiatus remained unclear," lead study author Matthew England said.
"But the heat uptake is by no means permanent: when the trade wind strength returns to normal -- as it inevitably will -- our research suggests heat will quickly accumulate in the atmosphere."
The strengthening of the Pacific trade winds began during the 1990s and is ongoing. Previously, no climate models incorporated such strengthening and so failed to capture the hiatus in warming, the researchers said.
"The winds lead to extra ocean heat uptake, which stalled warming of the atmosphere," England said. "Accounting for this wind intensification in model projections produces a hiatus in global warming that is in striking agreement with observations.
"Unfortunately, however, when the hiatus ends, global warming looks set to be rapid. This pumping of heat into the ocean is not very deep, however, and once the winds abate, heat is returned rapidly to the atmosphere."