To robust, or not to robust? … that is the question

From time to time it is suggested that ordinary least squares, a.k.a. “OLS,” is inappropriate for some particular trend analysis. Sometimes this is a “word to the wise” because OLS actually is inappropriate (or at least, inferior to other choices). Sometimes (in tamino’s humble opinion) this is because an individual has seen situations in which OLS performs poorly, and is sufficiently impressed by robust regression as a substitute, to form the faulty opinion that it’s superior to OLS generally. For the record, this comment is not one of those cases.

In reality, OLS is the workhorse of trend analysis and there are very good reasons for that. It’s founded on some very simple, and very common, assumptions about the data, and if those assumptions hold true, OLS is the best method for linear trend detection and estimation. It can be dangerous to use the word “best” in a statistical analysis, but in this case I feel justified in doing so.

Of course that raises some nontrivial questions. What are those assumptions? When might they not hold true? How could we tell? What should we do if we can establish that the OLS assumptions aren’t valid?

How fake skeptics fool themselves, part infinity: Sea Ice version

Suppose you were suffering from a serious illness which attacked many of your internal organs. It’s likely to be fatal, so your wife is very concerned about the results of your latest medical tests. They indicate that your heart, lungs, and liver are degrading rapidly, but that your spleen has actually improved. In fact your spleen didn’t show any signs of degradation, even over the long term. So you go home and tell your wife, “Great news, honey! My spleen is in better shape than it was before!”

That wouldn’t really be an honest report of your overall health, would it?

But that’s exactly what Anthony Watts has graced us — or should I say, disgraced himself — with, in his latest post about sea ice at WUWT. He crows about how much sea ice there is in the Arctic, and how it has reached “near normal” levels (remind you of anything?). But if Arctic sea ice is disappearing in a “death spiral,” how could one possibly do so? Well, if your heart, lungs, and liver are degrading rapidly, how could you possibly report that your health has improved? Talk about your spleen!

It’s easy. First, look only at a brief moment of time, quite ignoring what really matters, the trend. Second, look only at a small region of the Arctic, quite ignoring, well, most of it. Be sure to pick the one region that happens to show signs of improvement at this particular moment. It’s a classic strategy called “cherry-picking.” As for an overall survey of the state of Arctic sea ice and its statistically significant trends — we can’t have that! It would show just how dire the situation is.

Which goes to show that Anthony Watts is no skeptic. When he finds some excuse — any excuse — to blind himself to the obvious (that Arctic sea ice has been and continues to be one of the most compelling signs of global warming) Watts has no skepticism to apply. Instead he’ll bring his usual level of infinite gullibility. Honestly, it’s pathetic.

But it’s the same strategy that almost every fake skeptic has used (or should I say, abused) and many of them make their modus operandi. And well they should, because if you want to deceive the naive (including yourself), it works.

What has really been happening to sea ice lately that can tell us about the recent course of global warming?

Mathturbation King

Nicola Scafetta has published yet another paper about his theory that the (probably tidal) influence of Jupiter and Saturn is responsible for long-term changes in solar output, and that these cycles are responsible for climate change on earth. You can read about it on WUWT. It doesn’t surprise me that the paper is due to be published in a journal which seems to me to be sinking further and further into disrepute, the Journal of Atmospheric and Solar-Terrestrial Physics. Nor does it surprise me that there’s really no physics in the paper, just mathturbation.

How Fake Skeptics Fool Themselves, part 3

Jeff Condon seems unhappy with me. Enough to blog about it. And Anthony Watts cross-posts. But what I’d really like to discuss is yet another way in which Condon fools himself about trends in sea ice.

How Fake Skeptics Fool Themselves, Part 2

Jeff Condon didn’t seem pleased with my last post about his fake skepticism. He protested that all he had done was “plot some data in a reasonable fashion and make no conclusion.” I think his definition of “single-year ice” isn’t single-year ice and that single-year ice isn’t a good metric for the cryosphere anyway. I also think he selected his definition and presented his plot in order to imply an already-made conclusion. Could it be that he already had an opinion about sea ice, one based on faulty reasoning — the kind that fake skeptics use to fool themselves? Let’s take a look at another of his posts about sea ice.

How Fake Skeptics Fool Themselves

Anthony Watts has another post claiming that sea ice isn’t really doing anything worth worrying about. He includes much of the usual stuff, including a picture of the U.S.S. Skate which he originally stated was surfacing at the North Pole in March of 1959 to find lots of open water. But one of his readers pointed out that the photo wasn’t from 1959 and it wasn’t at the North Pole, so he changed his post (see the end of this for some interesting information). But that’s a minor point, what’s interesting is that he finishes by stating that “Global sea ice hasn’t varied all that much in 30 years, and I for one, am just not all that worried about it.” The claim is based on this post by Jeff Condon which Watts calls an “excellent essay.”

What Condon’s essay really illustrates is how fake skeptics fool themselves into thinking they have real evidence.