‘We are just seeing another pause in warming before the next inevitable rise in global temperatures …’
By Summit Voice
FRISCO — An acceleration of equatorial trade winds blowing from east to west has had a profound effect on global climate the past couple of decades, Australian researchers say.
The unprecedented wind shift appears to be the main reason for the temporary slowdown in surface warming the past 13 years, a period that has still included several of the hottest years ever for Planet Earth. The change in the wind pattern has resulted in heat being stored in the western Pacific — heat that’s likely to be released suddenly when the trade winds normalize, causing a spike in global temperatures.
“We should be very clear: the current hiatus offers no comfort – we are just seeing another pause in warming before the next inevitable rise in global temperatures,” said Professor Matthew England, lead author of the study and a chief investigator at the ARC Centre of Excellence for Climate System Science.
“Climate scientists have long understood that global average temperatures don’t rise in a continual upward trajectory, instead warming in a series of abrupt steps in between periods with more-or-less steady temperatures. Our work helps explain how this occurs,” England 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,” he said, explaining the findings published this week in the journal Nature Climate Change.
Essentially, the dramatic acceleration in winds has invigorated the circulation of the Pacific Ocean, causing more heat to be taken out of the atmosphere and transferred into the subsurface ocean, while bringing cooler waters to the surface.
“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. So global temperatures look set to rise rapidly out of the hiatus, returning to the levels projected within as little as a decade.”
The strengthening of the Pacific trade winds began during the 1990s and continues today. Previously, no climate models have incorporated a trade wind strengthening of the magnitude observed, and these models failed to capture the hiatus in warming. Once the trade winds were added by the researchers, the global average temperatures very closely resembled the observations during the hiatus.
“The winds lead to extra ocean heat uptake, which stalled warming of the atmosphere. Accounting for this wind intensification in model projections produces a hiatus in global warming that is in striking agreement with observations,” England said. “Unfortunately, however, when the hiatus ends, global warming looks set to be rapid.”
The impact of the trade winds on global average temperatures is caused by the winds forcing heat to accumulate below surface of the Western Pacific Ocean.
“This pumping of heat into the ocean is not very deep, however, and once the winds abate, heat is returned rapidly to the atmosphere” he concluded.