Oceans seem to explain the pause in global warming







FOR the past few years, one of the biggest puzzles in climate science has been: where did all the global warming go? Many scientists have thought that, if average surface air temperatures have barely increased, the extra heat must be going into the oceans, especially the largest, the Pacific. A new paper published in

Science

shows they are mostly right. Sea-surface temperatures have risen (blue line, top chart). And the heat content 1,500 metres below the surface (the brown line) has risen more than the heat in shallower waters, down to 300 metres (the red line). So more heat is being sequestered in the depths. What is surprising, though, is that the Pacific does not seem to be the world's heat sink: there, the heat content in shallow and deeper waters has risen in parallel (bottom right-hand chart). It is the Atlantic which plays that role. As the bottom left-hand chart shows, there, water 1500 metres down has warmed much more than the top 300 metres. And the period during which this has been going on (the past 15 years) more or less coincides with the period of the so-called global warming pause. For further explanation, see

our article in this week's issue