More than fifteen months ago I wrote the post “What of the Pause?”, where I tried to analyse the state of the global climate with a special focus on the interesting developments following the 2011/12 La Niña. I have also later discussed that particular time period here.
I have earlier pointed out the close connection between the SSTa in that central-eastern part of the narrow Pacific equatorial zone called “NINO3.4” and “global” SSTa over decadal time frames, how the former consistently seems to lead the latter in a tightknit relationship, firmly constraining the progression of global mean anomalies through time – flat (though with much noise) as long as the NINO3.4 signal remains strong enough to override (and/or control) all other regional signals around the globe, which most of the time it does.
I have then proceeded to show how “global warming” (or “global cooling”) only appears to come about at times when the influence of this tight relationship on the global climate is somehow offset by surface processes elsewhere, meaning outside the NINO3.4 region. This obviously doesn’t happen too often, because it would take a very powerful and persistent process to disrupt and even break the sturdy grip of the NINO3.4 region on the leash with which it controls the generally flat progression of global mean temps over time.
In fact, from 1970 to 2013 it evidently only happened three times. Which means that within these three instances of abrupt extra-NINO surface heat is contained the entire “global warming” between those years. Before, between and after, global temp anomalies obediently follow NINO3.4 in a generally (though pretty noisy) horizontal direction; no intervening gradual upward (or downward) divergence whatsoever.
With the year 2015 completed, I felt an update of this NINO3.4-global SSTa relationship was in order. Is there evidence of a new step as of late …?
My answer to this can only be: ‘It is still too early to tell.’ But interesting things have happened – and are indeed still happening – over the last two to three years, since about mid 2013:
As you can see, the last true step up in the mean global temperature level was back in 1998, in the wake of the great 1997/98 El Niño. This step was described and explained here.
Then, as you can see, there’s an attempt at a new upward shift in 2010, during the 2010/11 La Niña, just after the 2009/10 El Niño, but the global lift never materialised. Already in 2011, global SSTa was more or less back in lockstep with the NINO3.4 lead. The same thing, after all, did not happen post 1998 (nor post 1988). At those times, global SSTa remained firmly elevated (in 1998> by about 0.125°C) above the downscaled NINO3.4 curve after the initial surface heat accumulation:
Animation 1. The 1998 upward step in global temps. Watch how, as the NINO3.4 drops steeply into deep La Niña conditions just past the El Niño peak, global anomalies don’t follow and rather stay high for more than half a year before dropping. Because of this, they never quite manage to catch up before the tide turns once again …
What, then, happened during the equivalent “Niña-Niño-Niña” sequence twelve years later?
The same accumulation of surface heat outside the NINO3.4, but this time around the global curve falls directly back in line (during the first half of 2011). At least until 2013, when “The Blob” made its first appearance in the Northeast Pacific.
Here’s how global SSTa evolved over the last four years, since January 2012:
And the very same period graphed:
The red NINO3.4 curve falls well below the black global curve from about mid-2013, as “The Blob” starts making an impact, and stays there until the 2014/15 transition, when NINO3.4 finally catches up once more. Even though the tight relationship thus seems to have been all but restored, it probably isn’t quite, because in such case the red NINO curve would normally rise a fair bit higher than the black global one, simply due to the fact that the El Niño signal tends to be substantially stronger in the NINO3.4 region than globally (as you can easily verify from Fig.1 above), and also somewhat ahead of it, at least near the top.
It seems likely that there’s been an average global ‘lift’ in SSTa relative to the downscaled NINO3.4-curve over the last two to three years of about 0.05 degrees:
We will simply have to wait for the coming drop and see what happens next … 🙂