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11 January 2013

Heresy of the week: A pause in global warming is no cause for complacency

Warning: the following post contains science of a climatic nature and graphic references to mainstream scientific opinion. 

If you look at a graph showing changes in average global temperatures since the industrial revolution then two things immediately stand out: firstly, that the overall trend is undoubtedly upwards; and, secondly, that the trend, while unmistakable, is far from smooth – there are periods, some lasting decades, when temperatures remain pretty level.

According to the Met Office, it looks like we’re into one of those periods right now. Fred Pearce, in an article for New Scientist, takes up the story:

  • “Having calculated annual global temperatures for the next five years, its best guess is that they will be, on average, 0.43 °C higher than the average for 1970 to 2000. That's down from its previous prediction of a 0.54 °C rise. If the new prediction proves right, then 2017 will barely be warmer than most years in the past decade.”

So how can these stops and starts in the temperature record be reconciled with the much smoother upward trend in carbon dioxide concentrations – which are supposed to be the main cause of global warming.

The answer is that man-made impacts on the climate interact with purely natural influences to produce variations over the short-to-medium term:

  • “There is a growing awareness among climate scientists of the importance of natural variability in predicting climate change, especially in the short term, where it can completely obscure the global warming signal…
  • “Mostly [the sources of this variability] involve the movement of heat between the atmosphere and the oceans. The oceans are the sleeping giant of climate change. They act as a huge heat sink: 90 per cent of the heat generated by accumulating greenhouse gases is absorbed by the oceans. How fast this happens is variable, depending on ocean currents and other fluctuations.”

The cyclical nature of these fluctuations means that the currently higher-than-average cooling effect of the oceans is not only likely to prove temporary, but also reversible – what the oceans taketh away, the oceans giveth back.

The politics of climate change are notoriously local and short-term. Public support for action goes up in a heat wave; while scepticism flourishes in a cold snap. The prospect of several years of stasis, however certain to come to an end, will almost certainly undermine resolve on the issue.

This week on ConservativeHome, Andrew Lilico (who accepts the mainstream scientific position on climate change) argued that, for political and economic reasons, a pause in warming was all the more reason to scrap policies designed to tackle the problem.

There is, however, a danger of seeing this as a straight choice between doing what we’re trying to do at the moment and doing nothing at all. There are other choices. While technologies like nuclear and onshore wind power tend to get all the attention, some much bigger and more affordable reductions in carbon emissions have come about through energy efficiency improvements and, in the United States, a switch from coal to shale gas.

In view of the fact that the current pause is most likely a breathing space, not a permanent reprieve, we should seize the chance to actively rethink our approach. Alternatively, we could just sit on our hands and hope for the best.


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