The theme is encompassed in the title: “Record-smashing August means long-awaited ‘jump’ in global warming is here.” I’m skeptical.
The post says this:
As I reported last year, climatologists have been expecting a “jump” in global temperatures. There is “a vast and growing body of research,” as Climate Central explained in February 2015 that “humanity is about to experience a historically unprecedented spike in temperatures.”
It goes on to say:
A March 2015 study, “Near-term acceleration in the rate of temperature change,” makes clear that an actual acceleration in the rate of global warming is imminent — with Arctic warming rising a stunning 1°F per decade by the 2020s.
First let me point out that I dislike referring to a “March 2015 study” by linking to a Climate Progress blog post. It should link to the study itself.
Second, let me point out that “a stunning 1°F per decade by the 2020s” is neither an imminent consequence of accelerated warming, or something to expect “by the 2020s.” C’mon, guys, look at the data: Arctic warming has been happening that fast already.
The linear trend since 1990 puts the warming rate in the Arctic at 1.1°F per decade.
I mainly object to the level of exaggeration which I regard as misleading. For instance, the March 2015 study does not make it clear that “an actual acceleration in the rate of global warming is imminent.” It presents some evidence (computer model simulations) and makes a viable argument … but “makes it clear”? No.
As for “a vast and growing body of research,” that “humanity is about to experience a historically unprecedented spike in temperatures,” as far as I can tell that just ain’t so. There’s research to that effect and research contrary to it. In my opinion, the claim is just exaggeration.
But probably the most clearly wrong statement in the whole post is in its title: that the record-smashing August means the jump is here, now. No, it doesn’t, a single hot month or string of hot months or years doesn’t do that, any more than a cold month or string of cold months or years would disprove global warming.
It’s the “hiautus/pause” mistake, in reverse. I’ve spent years knocking down the “pause” nonsense we had to put up with from deniers. As for “acceleration,” let’s freely discuss the possibility but let’s not declare it a fact, until the evidence is really there. It isn’t, yet.
Here’s the annual average global temperature since 1970, including this year in spite of the fact that 2016 isn’t over yet:
The most recent value is farther above the trend line (shown in in red) than any other. Does this “make it clear” that acceleration is “imminent?” No. It’s possible, but we don’t know yet. This year, as high above the trend line as it is, isn’t enough to justify claims of a trend change statistically. If we look at the residuals from the linear trend it’s very suggestive:
But “very suggestive” is not “makes it clear.” Furthermore, the extremity isn’t out of line with what one could expect if the residuals follow the normal distribution. This is well visualized with something called a “quantile-quantile plot”:
It’s well quantified by testing the normality of the residuals with the Shapiro-Wilk test. With a p-value of 0.43, it’s not even close to statistically significant evidence of significant departure.
As for other tests for departure from the linear trend, of which there are many, none of them gives the evidence required.
It’s a pity, because we don’t need to exaggerate the warming rate … the present rate is plenty scary enough. It’s more the pity because if the coming years show claims of acceleration to be as mistaken as claims of the “pause” were, it’s an embarrassment, and gives plenty of ammunition to deniers to crow about how climate bloggers overstate the changes in their unbridled alarmism.
Please, please, we don’t need to exaggerate. We definitely don’t need to claim as “clear” and “imminent” things for which the evidence isn’t yet there. What we already have the evidence for, is scary enough.
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