Question: How does a dumb claim go from just a dumb claim, to accepted canon by the climate change denialati?

Answer: Repetition.

Yes, keep repeating it. If it’s contradicted by evidence, ignore that or insult that. Repeat it again. If you’re asked for evidence, ignore that or insult that, just keep repeating it. That’s how things get burned into brains.



Case in point: Bob Tisdale has joined the brigade quoting Judith Curry’s bold claim that “early 20th century global warming … is almost as large as the warming since 1950.”

So I asked him, over at the WUWT blog, how much the early warming was, and how much warming we’ve had “since 1950.” I asked politely. He replied that he was sure I could do it myself, and he had no need to waste his time with something so simple.

So I asked again. I mentioned that he had quoted Curry himself, and had thanked her for the post which it begins, suggesting he agreed with her claim. I asked him whether or not that was the case. And I asked about how his numbers might support or oppose such a claim. I mentioned that my readers might be suspicious of his avoiding answering.

He replied again, saying that he had signed his previous response “Adios” because he was saying “good-bye” and he meant it. He added some stuff about climate models, which was not the topic I was asking about. It’s an interesting topic, I might post about it soon, but it had nothing to do with the questions I had asked.

In my opinion, “Adios” is his way of avoiding the issue. Also in my opinion, he wants to avoid it because he doesn’t use “skepticism” when it comes to claims from Judith Curry, especially when he likes the implication of “almost as large.” He never even bothered to find out whether or not it’s true.

Also my opinion: Judith Curry never bothered to find out whether or not it’s true either. She certainly didn’t mention how much the early warming was, or how much “since 1950,” despite the fact that it was the entire topic of her own post (that Tisdale quotes).

If you’re going to claim that “A” is “almost as large” as “B”, shouldn’t you be able to answer the questions: “How big is A? How big is B?”

But — Judith Curry says so, others repeat it, some (like Tisdale) are inspired by it, with new fodder for other attacks on the science of climate change. Curry’s original claim, which I have yet to see her provide any evidence for, is morphing from the simple bullshit it was at the start, to the kind of “canon” among deniers that feeds their lust for denial.

As for the two warming episodes (early and late), I’ve done a lot of analysis of that, but rather than repeat the numbers, I’ll just show the graph. I’ll use annual average global temperature anomaly from NASA (Bob Tisdale seems to like that choice). I’ll plot it as a black line, from the year 1910 up to 1970 (which includes the “early 20th century warming”). Then I’ll plot it again, as a red line, but shifted back in time and down in temperature, so we can directly compare how the early warming (in black) compares to the later warming (in red):

Or, let’s try this graph:

Was the early 20th century warming “almost as large” as the warming “since 1950”? You make the call.

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