Update on the relationship between the NINO3.4 and global SSTa

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:

NINO vs. gl

Figure 1.

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“The Blob” and global SSTa since 2010

Global SSTa has really been ratcheting up now for a while. At the moment, the strong ongoing El Niño is doing most of the work, but there is no question that even this has been provided with a significantly elevated baseline from which to soar, a raised mean level seemingly establishing itself already years before the current El Niño started moving.

Well, it just so happens that this new level is higher than the old one by quite exactly 0.1 K. How can one tell?

Like this …

We noted and discussed already a year ago how the global lower troposphere has yet to respond to the conspicuous and mostly extratropical accumulation of surface heat in the NE Pacific basin starting in mid 2013.

Under the working hypothesis that this abnormal and persistent NE Pacific surface heat phenomenon (often simply nicknamed “The Blob”) is responsible for the entire 0.1K lift in the mean level of global SSTa since 2013, and positing that the lower troposphere has not yet responded to it, hence giving rise to the distinct divergence seen over the last couple of years between the “gl SSTa” and “tlt” curves, we lower the former en bloc by 0.1K from July 2013 onwards (yellow vertical line in Fig.1) and superimpose it on the latter: Continue reading