Global Warming hiatus due – surprise! – to Atlantic Ocean

A humpback whale feeding off the coast of Newfoundland on Canada's Atlantic coast. Photo by Greg Locke © 2014

A humpback whale feeding off the coast of Newfoundland on Canada’s Atlantic coast. Photo by Greg Locke © 2014

New research published today in the journal Science suggests, surprisingly, that the answer to the biggest climate change mystery of the past decade or so may be found in the deep Atlantic Ocean, and not as suspected in the Pacific. Noted Science:

Why did the rapid global warming that characterized the latter part of the 20th century slow down over the last 15 years or so? Many different theories have been proposed, but a new study suggests that a massive movement of heat from shallow surface waters to deep regions of the Atlantic and Southern Oceans — but not the Pacific Ocean, as many researchers had predicted — might be responsible.

Xianyao Chen and Ka-Kit Tung analyzed data from profiling floats, or oceanographic sensors that can move vertically throughout the water column, and traced the pathways that heat has taken through the world’s oceans since the turn of the 21st century. The oceans are capable of storing about 90% of the world’s surface heat content, and the researchers suggest that most of the excess heat that would have otherwise continued to fuel global warming is currently stored in the basins of the Atlantic and Southern Oceans. The researchers also suggest that a sudden shift in salinity that corresponded with the slowdown of global warming at the beginning of the 21st century may have triggered this migration of heat to deeper waters. Historically, similar events have lasted 20 to 35 years, according to Chen and Tung. Consequently, the researchers suggest that global warming will pick back up in 15 more years or so, when heat returns to the surface waters.

F&O publishes an analysis of the findings in Dispatches/Science, by Richard Allen, professor of climate science at the University of Reading: Does deep Atlantic heating account for global warming hiatus?  (free story, via The Conversation). Excerpt:

There seem to have been a dozen or so explanations for why the Earth’s surface has warmed at a slower rate over the past 15 years compared to earlier decades. This is perhaps not so surprising given the complexity of the climate system – the world’s best detectives will inevitably struggle to disentangle the factors which influence every lump and bump in the surface temperature record.

However, recent research implicates natural changes in the Pacific and Atlantic oceans as the prime culprits. Just as the apparently random motions in a river’s flow can shift before our eyes from one minute to the next, the gradual sloshing about of our vast ocean waters can influence Earth’s climate from one year to the next and from one decade to the next.

It is clear that natural variability has and always will influence the climate … continue reading Does deep Atlantic heating account for global warming hiatus? (free story)


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