Our Blog

New ocean readings may explain global warming “pause”

20140823_STD001OVER the past few years one of the biggest questions in climate science has been why, since the turn of the century, average surface-air temperatures on Earth have not risen, even though the concentration in the atmosphere of heat-trapping carbon dioxide has continued to go up. This “pause” in global warming has been seized on by those sceptical that humanity needs to act to curb greenhouse-gas emissions or even (in the case of some extreme sceptics) who think that man-made global warming itself is a fantasy. People with a grasp of the law of conservation of energy are, however, sceptical in their turn of these positions and doubt that the pause is such good news. They would rather understand where the missing heat has gone, and why—and thus whether the pause can be expected to continue.

The most likely explanation is that it is hiding in the oceans, which store nine times as much of the sun’s heat as do the atmosphere and land combined. But until this week, descriptions of how the sea might do this have largely come from computer models. Now, thanks to a study published in Science by Chen Xianyao of the Ocean University of China, Qingdao, and Ka-Kit Tung of the University of Washington, Seattle, there are data.

Dr Chen and Dr Tung have shown where exactly in the sea the missing heat is lurking. As the left-hand chart below shows, over the past decade and a bit the ocean depths have been warming faster than the surface. This period corresponds perfectly with the pause, and contrasts with the last two decades of the 20th century, when the surface was warming faster than the deep. The authors calculate that, between 1999 and 2012, 69 zettajoules of heat (that is, 69 x 1021 joules—a huge amount of energy) have been sequestered in the oceans between 300 metres and 1,500 metres down. If it had not been so sequestered, they think, there would have been no pause in warming at the surface.

Click here to read more from this August 23, 2014 Economist article.

Tags: , ,

This is a unique website which will require a more modern browser to work! Please upgrade today!