Sunday, May 31, 2009

some sniping at peer-reviewed AGW science

The discussion of AGW at Overcoming Bias refers to a Physical Review Letters paper by Verdes. The first link to the paper in the Overcoming Bias post doesn't work for me, the second link costs money, but in the comments, commenter "g" gave a variant of the first link which works and is free.

The fit in the Verdes figure reproduced by Robin Hanson looks pretty good, probably about as good as can be expected given the quality of the experimental data. But it is not clear to me that it can remain so good outside Verdes' chosen interval.

At the high end: cutting off around 2001 in a paper submitted in 2006 seems peculiar, especially when linear extrapolation suggests that by 2005 the model might be diverging by more than it does in any of the years when Verdes chose to test it. And today we have data up to 2008, and it might be interesting to calculate what the Verdes model infers the CO2 level have been up to 2008. I'd rather expect it to diverge further (from skimming his description of his model, and noting that global temperatures have remained well below the strong-AGW projected long-term trend).

At the low end: while it seems fairly natural to stop fitting sometime in the 19th century (as data quality is falling fast in that period) it is not obvious that one should also stop testing the model sometime in the 19th century. There is a controversy about how much climate variability there has been in the last 1000 years, fanned by IPCC AR3 and An Inconvenient Truth promoting the famous low-variability "hockey stick" reconstruction. Since those heady days of settled science, IPCC has backed off to the variability illustrated in Fig. 6.10 of the AR4 report. It's not obvious that before 1800, when anthropogenic CO2 forcing is negligible, the Verdes model can produce as much variability as AR4 estimates to have existed. (And various IPCC critics, like me, doubt that AR4 has gone far enough: I hope that Robin Hanson will put his econophysicist hat on and make a nice time machine for betting markets, so that we can make and cleanly settle bets about pre-1800 variability.:-)

Also, setting aside concerns about the arbitrariness of the test window, is the fit good enough to justify the title "Global Warming Is Driven by Anthropogenic Emissions," and the concluding sentence of the abstract?

Here we show, using two independent driving force reconstruction techniques, that the combined effect of greenhouse gases and aerosol emissions has been the main external driver of global climate during the past decades.
That's a pretty strong statement. If we quantified the goodness of the fit over the three wiggles of the low-frequency signal within the window, would it be enough decibels of evidence to fairly paraphrase as "show ... has been the main external driver"? If I were an advocate seeking to make the most of this analysis, I might paraphrase it as "strongly support" the conclusion, rather than "show" the conclusion.

Thursday, May 21, 2009

nifty nonlinearities

Snow rollers. Who knew? Not me, anyway.

(h/t Watt's Up With That)

Wednesday, May 20, 2009

two very nifty complexity theorems

theorems #2 and #3 here

(also one theorem, #1, that I can't appreciate and can't follow the proof of; and two theorems, #4 and #5, where the definitions used are new to me and I'm having trouble seeing the significance)

Incidentally, I don't find them sidesplitting as Aaronson does. YMMV, but if I were looking for a word for what he seems to be trying to get at, I'd probably call them something like "twisty" or "subversive," not sidesplitting.

fascinating artifacts, difference in perspective

Reading John McWhorter's TNR post on the significance of the "prehistoric pin-up" reported in Nature I was struck by McWhorter's remark that

It has actually been long established that the earliest evidence of artistically conscious humans has been found in, as we might expect, Africa, given that it's where our species emerged. Specifically, South Africa, in Blombos Cave. There were beads made from shells, and geometric engravings on ochre --- i.e. slam-dunk "modern" tokens, unimaginable of even the smartest dog, parrot, chimp, or even Australopithecine "Lucy." And this stuff dates back to 75,000 to 80,000 years ago. No bosomy figurines, sure --- but if what got dug up in Germany was jewelry and etchings instead, we can sure there would be the same claims that here was the birth of advanced thought.

I knew very little about prehistoric art, so I had to do a little searching before I could compare the Blombos beads and engravings to Nature's new figurine. I was surprised to find that what McWhorter derides in his article as "socially unsavory," the "fetishization of artistic tokens dug up in Europe from a few tens of thousands of years ago," is exemplified by John Noble Wilford referring to "inspiration and symbolism behind the rather sudden flowering" behind the difference between this and this. I don't know about "sudden" (as per my caveat below about archaeological evidence trends being tenuously related to real trends) but referring to that difference with "flowering" or even stronger words seems quite reasonable to me.

To me, the new figurine looks like something that none of the characters in Lord of the Flies would have been able to make, while the Blombos etchings look like something the characters in Lord of the Flies wouldn't have bothered to make. And the Blombos beads are nifty, and significant, but (1) it is not obvious to me how to compare the significance of decoration to the significance of representational art, and (2) I don't know how hard it is to punch holes in shells using primitive tools, but I wouldn't be terribly impressed if a Lord of the Flies character made them in a few afternoons.) Therefore, when McWhorter says "if what got dug up in Germany was jewelry and etchings instead, we can be sure there would be the same claims" I think it seems to say more about the intellectual dishonesty of the accuser than of the accused.

When I look at artifacts like the new figurine, I feel the same puzzlement I feel when I read about ancient China or Rome: it makes me start scratching my head, wondering what developments were missing to keep the next revolution from starting. What kept the erotic figurine makers from going on to an agricultural revolution? What kept China or Rome from going on to an industrial revolution? (I do know some of the stock answers to the second question, but I don't consider the question completely settled, especially for China.) Looking at the Blombos artifacts doesn't give me the same feeling --- the artifacts seem very impressive and significant in the way that firemaking or weaponmaking or clothing are very impressive and important, but they don't seem very much like the work of modern humans marooned in the Stone Age.

(disclaimer: I'm not trying to argue against all of McWhorter's points, just his "fetishization" smear of what I see as an obvious conspicuous difference. In particular, I basically agree with his point about geographical distribution of artifacts not necessarily resembling the underlying historical reality. Accidents and unexpected cross-correlations can skew the distribution of artifact-like evidence very dramatically, and the problem can get worse when researchers start seeing what they expect to see and/or publishing what others want to hear. Such caution is important in lots of observational sciences, not just paleoarchaeology, e.g., trying to understand astronomical trends or climate trends or ecological trends or economic trends from the accidentally biased data that we have.)

Wednesday, May 13, 2009

This being the Internet

Since I have been dumping on The Economist, it is now my solemn duty to try to be snarky about silly usage errors on their part.

"There is a widely pedalled myth that China’s growth depends on American consumers."
(h/t Carpe Diem) And then as the great mythic wheel of Internet karma is peddled, I will presumably be pwned for usage errors too.

an interesting line of questioning

Mankiw channels Popper:

Going forward, what macroeconomic data would you have to observe before you concluded that the stimulus bill has been a failure? Or will you conclude, no matter how bad things get, that the economy would have been in even worse shape without the stimulus? And if the latter is the case, aren't these quarterly reports just a bit surreal?

Tuesday, May 12, 2009

With friends like these

Besides my remarks earlier about the surprising applause lines, I was surprised by The Economist's extraordinarily limp defense of "the more liberal Anglo-Saxon model." "This newspaper stands firmly on [its] side," the authors declared in their p. 13 editorial, the editorial explaining the cover illustration of a French model grinning down at the Anglo-Saxon model from head and shoulders and indeed shoes above. And, in an article devoted to how unfolding economic outcomes have discredited the Anglo-Saxon model, the authors could find nothing about the current economic outcomes to say in defense of the model. Such loyalty, to loyally announce that you are paid to defend it! So damning of the Anglo-Saxon model that even those who take money to defend it can find no defense!

To pick on one passage, "Mr. Obama is right to admit that in some ways Continental Europe has coped well. Tough job-protection laws have slowed the rise in unemployment." This is probably literally true. But it's hard to imagine why people firmly on the side of the more liberal Anglo-Saxon model would choose to describe it in this extraordinary way. I don't know where to find comprehensive time series data, so I Googled for "France unemployment" and "USA unemployment" pages dated within the last month. Evidently in March official unemployment was 8.2% in France and 8.5% in the USA. This isn't good for the USA, but neither does it deserve mention as how Continental Europe has coped well. An 0.3% difference is well within the uncertainty of how unemployment should be defined, and measured, and compared across significantly different populations. (E.g., the two countries don't have the same age distribution, and the US doesn't participate in anything much like the intra-EU labor migration system.) In my opinion, it would be essentially as accurate to say "the crisis has caused US employment rates to rise as high as the chronically high rates of France." It might be worse for other Anglo-Saxon countries, but (1) Obama was specifically mentioned here, and (2) I don't see the definitive list of which countries are included in the Anglo-Saxon model basket and (3) even if the USA were the only one whose unemployment comparable to France, the USA will be a pretty sizable fraction of any possible basket. Thus, this statistic is a bizarre way to support the elevation of the French model.

There are all sorts of economic uncertainties about how bad the current economic problems will get. There are also all sorts of political uncertainties about how much further Obama and the Democratic Congress will move the USA away from "the Anglo-Saxon model." Perhaps in a few months the Anglo-Saxon economies will have suffered much more, and the Continental economies will have suffered much less. Perhaps over those months the US system will not have become significantly more Continental (e.g., not much more politicization of capital allocation, and no passage of card check with mandatory wage arbitration). If so, then perhaps a dirigiste triumphalist article like this could make a lot of sense. At this time, though, not so much, and it seems quite strange that people who profess to analyze the economy, much less people who profess to favor the Anglo-Saxon model, should choose to justify a cover image like with an article built on comparisons like this.

Which side is your choir on, boys?

Which side is it on?

I skimmed The Economist last week and this week. I found myself surprised by some of their throwaway partisan applause lines. The lines seem like sloppy surely-we-are-all-on-the-correct-side-of-this-issue preaching to the choir. That, alas, doesn't surprise me. (I grant the The Economist can be less cavalier about that than many magazines. That's damning with faint praise if there ever was.) But I am surprised at their implicit assumption about the partisan sympathies of their choir. What happened while I wasn't looking? The choir they seem to be expecting doesn't match what my mental model for who subscribes to The Economist.

One surprising line is on page 13 of the May 9 issue. "Thirty years after Thatcherism began to work its cruel magic in Britain (see page 60), continental Europe still tends to favor a larger state." Are they casually taking a side-swipe at the obvious overall cruelty of a smaller state and/or of Thatcherism? Some audiences would consider that to be controversial, not obvious. Damned few would claim there were no downsides to Thatcherism, of course. But some would dispute that they were particularly cruelly distributed, especially since the outcomes of the kinds of policies that Thatcher fought against have been seriously flawed as well.

E.g., high unemployment in France's rigidly controlled labor market has not been good for the poor. Even the same editorial acknowledges the very high unemployment concentrations in youth (over 20 percent) and various Muslim areas (over 40 percent). That outcome alone bears comparison with various negative outcomes associated with Thatcherism. If such unemployment were present in England (or the USA) and absent in France, I expect it would rank very high on any passionate leftist's list of flaws of Thatcherism (or the USA). (And indeed, now that economic upheaval has raised USA unemployment to the level of France, the paid defenders of the Anglo-Saxon model at the The Economist refer to this this as a notable disadvantage of the USA's approach; that is, a notable disadvantage relative to France! See my following post.)

Conceivably the "cruel magic" line is intended to be ironic. The authors could be using a light touch to express what could be heavy-handedly expressed as "after 'cruel' Thatcherism began to work its magic." But if so, the touch is so light that I can't feel it even when I try. It really seems to me that that line is an intended as an earnest reminder that obviously Thatcherism is particularly cruel.

(Now, denying passports and work visas and whatnot to subjects in Hong Kong as the lease expired, that was particularly cruel and particularly shoddy. But that's not what people usually mean by Thatcherism.)

Another surprising line is in the April 25th issue, in the cover editorial on p. 13: "The Depression showed how damaging it can be if governments don't step in when the rest of the economy seizes up." This line might be less controversial than the "cruel magic" line. Still, it's a funny thing to state as simple fact if you know the kind of person who reads Milton Friedman, or Amity Shlaes, or real business cycle theory, or George Selgin. Those are not terribly popular views, but they are not terribly marginal or terribly ignorant either.

Also, while right-thinking people have long considered the Depression to be clear evidence for the importance of governments artificially stimulating economies, the very length of this history can be a bit of a problem, because stimulus fans who argued for their models by back-fitting the Depression have had several sieze-ups since then when their policy prescriptions could be tried. They famously encountered difficulties in the 1970s in industrialized countries. As far as I know it's hard to consider their record in the Third World in any decade to be a success. And while there's considerable disagreement about what lessons to draw from Japan's lost decade, I think one plausible lesson is that even by 1990 even the broadest outline of how to un-stick a stuck economy was not very well understood.

Against that history, a possible triumph is that governmental manipulations broadly consistent with the Great Depression stimulus lesson might deserve much of the credit for "The Great Moderation". But as Bernanke was at pains to acknowledge in the given link, as of 2004 there was some difficulty in assigning credit. And measuring possible costs is even harder. At one extreme, continuing "small" costs (in the sense of being too small to measure easily) could be quite significant in economic outcomes. E.g., US macroeconomic policy has tended to discourage private savings and investment. It's hard to be sure that hasn't caused a penalty rather more than 0.1% in annual economic growth; that would add up. And at the other extreme, occasional huge costs can also be proverbially tricky to estimate: how often will the steamroller catch you just as you are trying to get away with your latest shiny penny?