Latest Attempts To Explain Global Warming Pause Fall Flat

  • Date: 06/03/15
  • Judith Curry, Climate Etc.

Two new papers were published last week of relevance to the hiatus. The inference is that the pause has now been explained; and that it should end soon with a warming ‘burst.’

For background, see my invited presentation to the American Physical Society on this topic: Causes and implications of the pause.

First, lets take a look at the ‘spin’ surrounding this issue and these papers:

Climate Central:  Looming warming spurt could reshape climate debate

Scientific American:  The pause in global warming is finally explained.

Quartz:  Scientists now know why global warming has slowed down and its not good news for us

The titles pretty much speak for the articles: The inference is that hiatus has now been explained; and that it should end soon with a warming ‘burst.’

And now for the spin-free zone.  Lets take a look at these two papers and see what we can actually infer and and learn from them. […]

JC reflections

I found the Palmer et al. paper to be interesting, in that given a 15 year hiatus, that the models predict a 25% chance of 5 more years.  My take on how the pause will play out is summarized in the stadium wave post:     I expect that the natural variability will contribute to a continuation of the hiatus into the 2030’s, with solar and volcanoes being a wild card.

With regards to the Steinman and Mann paper, they state in the Penn State press release:

Using a wide variety of climate simulations, the researchers found that the AMO and PMO are not significantly correlated; they are not part of the global “stadium wave” oscillation, as some researchers had claimed.

Their arguments are based on the assumption that model simulations provide ‘correct’ estimates of both the forced signal and the correct level of intrinsic multidecadal variability. The Kravtsov et al. paper shows that this assumption is not justified.

Brilliant to use climate models that don’t correctly simulate internal variability, particularly the PDO, to claim that the AMO and PDO aren’t correlated and not part of a stadium wave oscillation. /sarc   The stadium wave paper showed that it is  the lag that gives rise to maximum correlation between the AMO and PDO.  Steinman and Mann conclude that the linear detrending is likely to cause artificially high observed (lagged) correlations between the AMO and PDO  in the stadium wave.

So where does all this leave us?  Internal variability only partly explains the pause – how big that part is remains somewhat unclear, but there is growing evidence that it is the major cause of the pause.  The critical issues are how long will the pause last, inability of climate models to simulate a pause beyond 20 yrs with increasing CO2, and what will happen once the internal variability flips to a warming situation.

Is there a looming ‘warming spurt’ at the ‘end’ of the pause?  Maybe, but it depends on what is going on with the sun.  Many solar scientists expect a coming solar cooling.  How increasing CO2, solar cooling and internal variability will play out in terms of influencing the global climate over the next several decades is of central importance to our understanding of the climate system, which still has substantial uncertainties (no matter what the IPCC, EPA etc say).

Bottom line: The pause in global warming is NOT finally explained.

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