The (Latest) Answer To the “Pause”

  • Date: 26/08/14
  • Dr David Whitehouse

In popular science journalism the latest is always the best. With all the explanations for the “pause” in global surface temperatures since 1997 – there are now over 30 of them – it is always the most recently published one that is the “answer.”

This time it’s the Atlantic Ocean that’s to blame. A paper published in Science says that a 30-year periodicity warms and cools the world by sequestering heat below the ocean’s surface and then releasing it.

The paper concerned is not an impressive one. It starts off assuming the answer it seeks and finds it! Since the emphasis is on the Atlantic take a look at their data for surface temperature and ocean heat content (OHC.) As you can see OHC is declining, as the surface temperature remains static. Incidentally, a few error bars on the graphs would have been illuminating and would have altered a false impression given by the graphs data’s precision. Click on image to enlarge.

Screen Shot 2014-08-26 at 20.21.24

The OHC data comes from the Argo array that has been in place for about a decade. When talking to people about Argo I have heard many comments about how it is obviously showing a global increase in OHC over that period but this is something that is not entirely born out by the data, and will be the subject of a future post.

Before the Atlantic it was the Pacific storing heat beneath the waves and taking it away from the atmosphere. Some scientists were quite confident that it was at the root of most of the “pause” and some still are despite the recent attention on the Atlantic Ocean. Even the authors of the recent Science paper say they are “not downplaying the role of the Pacific.” So there you have it. It is the Atlantic that is the cause of the “pause,” and it is the Pacific that is the cause of the “pause” as well. I’m glad that’s clear.

For those who are impressed with some of the media’s reports that the “pause” has its best explanation to date there are two papers, here and here, published in Nature Climate Change at the same time that say it is, most definitely, due to the Pacific.

The language of science journalism is interesting here. Note that the “pause” has been “seized” upon by “climate change sceptics and puzzled scientists,” and that the “pause” happened after “decades of rapid warming.” (Note to Editor: recent warming started around 1980. The 80s hardly saw “rapid warming” and the warming had stopped by the later half of the 90s.)

You don’t have to look very deeply at the science to realise that, despite the headlines, no one has come up with an answer to the “pause.” Some place their faith that there is a major driver – the Atlantic or the Pacific for instance – that can explain most of it. Others admit that there will not be any one cause for the “pause” and that it is likely to be the result of a patchwork of influences. If so then they have to explain why such a patchwork has for 17 years kept the global surface temperature statistically flat in the face of rising greenhouse gas concentrations – surely one of the most remarkable balancing acts in the history of science.

For many the proof of what is causing the “pause” will not be forthcoming until it goes away and what is expected to be accelerated global warming resumes. But since whatever the culprit is would have been a very significant contributor to the pre “pause” warming in the 80s and 90s, one wonders how swift will be that acceleration?


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