The Role of the World's Oceans in the Global 'Warming Hiatus'

Most are aware of the "warming hiatus" that has slowed down warming temperatures of the past decade. Now, though, scientists have taken a closer look at the role that the oceans played in this hiatus.

Our Earth's oceans possess the ability to absorb heat. Believing that this may partially explain the warming hiatus, researchers used data from a range of state-of-the-art ocean and atmosphere models. More specifically, they calculated the change in the amount of heat entering the ocean with the model. Then, they compared this estimate with results from an ocean model-data synthesis and a leading atmospheric model-data synthesis.

"This study attributes the increased oceanic heat drawdown in the equatorial Pacific, North Atlantic and Southern Ocean to specific, different mechanisms in each region," said Sybren Drijfhout, one of the researchers, in a news release. "This is important as current climate models have been unable to simulate the hiatus. Our study gives clues to where the heat is drawn down and by which processes. This can serve as a benchmark for climate models on how to improve their projections of future global mean temperature."

Previously, the drawdown of heat by the Equatorial Pacific Ocean over the hiatus period, due to cool sea-surface temperatures associated with a succession of cool-surface La Nina episodes, was thought to be sufficient to explain the hiatus. The new analysis, though, reveals that the northern North Atlantic, the Southern Ocean and the Equatorial Pacific Ocean are all important regions of ocean heat uptake; each basin contributes roughly equal amounts to explaining the hiatus, though the mechanisms of heat drawdown are different and specific in each basin.

"The deeper understanding gained in this study of the processes and regions responsible for variations in oceanic heat drawdown and retention will improve the accuracy of future climate projections," said Bablu Sinha, one of the researchers.

The findings are published in the journal Geophysical Research Letters.

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