Global warming deniers really hate the fact that a proper comparison of computer model projections to observations does not show that “models fail.” But they love faulty comparisons.



One such faulty comparison was discussed here, which shows — among other things — that when comparing two series, you shouldn’t align them using a single year for alignment. That’s because a single year is bound to be either hotter-than-trend or colder-than-trend, which will bias the comparison.

Now Bob Tisdale has joined the chorus of those who object. His reason? The claim that



The reality: 1990 was an ENSO-neutral year, according to NOAA’s Oceanic NINO Index. Therefore, “1990 was…” NOT “…an especially hot year”. It was simply warmer than previous years because surface temperatures were warming then. I’m not sure why that’s so hard a concept for warmists to grasp. The only reason it might appear warm is that the 1991-94 data were noticeably impacted by the eruption of Mount Pinatubo.



Yes, you read that right. He says that 1990 was not an especially hot year. His evidence? That 1990 was not an el Nino year. Which he follows with “Therefore….”

We know that el Nino can make a year especially hot, just as la Nina can make it especially cool. We know that a warming trend makes later years likely to be hotter than previous years. But we also know — and either Tisdale does not, or he’s just pissing on your leg and calling it “rain” — that years can be especially hot or cold simply due to random fluctuation of temperature, in addition to those factors.

So: if you want to know whether a given year was especially hot or not, don’t look at some el Nino index and then declare “Therefore…” Look at the temperature. Unless, of course, your goal is to piss on somebody’s leg and tell them it’s raining.

Here’s global temperature data from NASA, together with a smoothed version so we’re not tripped up by the global-warming trend:

I put a red circle around the data for 1990. Notice how it’s noticeably above the trend line? That’s because 1990 was “especially hot.” Not just hot because the trend was going up, as Tisdale claimed. Especially hot in addition to the existing trend.

Here are the residuals — the departures from the smooth trend line:

I put a red circle around the residual for 1990. Notice how it’s noticeably above zero? That’s because 1990 was “especially hot.” Not just hot because the trend was going up, as Tisdale claimed. Especially hot in addition to the existing trend. As a matter of fact, it’s the 10th-hottest departure from the smooth trend in the 133-year data record from NASA.

But Tisdale doesn’t even want us to use the actual trend, because that might not “look right” since the eruption of Mt. Pinatubo caused cooling after 1990. OK. Let’s just look at 1975 through 1990 — no interference from Mt. Pinatubo — and let’s just use a simple linear trend rather than any of that fancy “smooth trend” stuff. Here’s what you get:

I put a red circle around the data for 1990. Notice how it’s noticeably above the trend line?

Yes, 1990 was “especially hot,” and not just because of the warming trend, it was so in addition to the warming trend. But Bob Tisdale and his ilk are so determined to deny anything — anything! — which befuddles their smear campaign, that they’ll deny even that. Try to stay out of the “rain” …

While we’re on the subject…