Yesterday, I talked about why Popper was wrong about how to tell science from pseudoscience. Today I'm going to contradict myself and talk about why he was right, and why I think climate science is still science.

The reason Popper is so tantalizing is that he was clearly on the right track. If your scientific theory cannot be falsified no matter what happens, it doesn't make useful predictions. Astrology, for instance, can never be proved wrong. If an astrologer tells you you'll fall in love and you don't, that doesn't invalidate astrology, it just shows that she forgot to consider that Venus was in Sagittarius or something. There's clearly something fishy and nonscientific about that.

The problem with Popper's account is that he thought that there would be one moment, one experiment that would show that something was right or wrong. But science doesn't work that way -- it takes a lot of little niggling problems to show up that don't quite fit with the theory, and then some new theory will come along that explains all those things. This can take a long, long time -- it took 230 years for Newton's theory of gravity to get replaced. Or it can happen quite quickly, especially for new theories in experimental fields. But in order for those niggling problems to accumulate, there must be testable predictions, things that can be wrong. If your theory is so broad that it never can be proved wrong, it's not science.

This is why I think climate science is doing the right thing, and I'm more skeptical about evolutionary psychology. Climate scientists produce lots of testable predictions: that's what climate models are for. It's true that it's very hard to falsify any particular model, because the predictions are noisy and the actual results are noisy, and so they don't have to be all that close to overlap. In other words, one or two years of results aren't going to be convincing to someone who thinks the model is doing something right.

On the other hand, over a span of several or many years, it will become clear which models are working well and which ones are not. Even now, models are going obsolete every year as predictions get refined, and as models take into account more variables and gain more granularity. I certainly think there's some chance that the current warming trend is temporary variation, though I think it's small. I think there's almost no chance that the field is going away, or that it will somehow fail as a branch of science.

On the other hand, I'm not so sure about evolutionary psychology. I know a lot less about it, so I could easily be wrong, but as far as I know, they mostly use it to explain existing facts. As in, "women seem to be more social and less visio-spacial than men, let's think about our evolutionary history and see if there's an explanation there." The problem with that is that it's very easy to look at a super complex system like our evolutionary history, especially when it's based on ideas of how we lived in prehistory for which we don't have direct evidence, and explain anything you want. My sense is that if we discover tomorrow that girls are better at geometry after all, we could pretty quickly come up with an evolutionary psychology explanation for it.

Of course, there certainly are some testable predictions. The biggest success is in cheater detection -- evolutionary psychologists came up with a novel explanation of a puzzling psychological result, which is that people have a natural propensity for figuring out if someone is cheating on a social contract. Then they tested their theory with new experiments against the existing theories, and were shown to be right [1]. But even this is mostly a new explanation of an existing result, not really a new prediction of human behavior.

On the other hand, evolutionary psychologists are pretty clearly on to something. We know that evolution can change mental abilities, so you would certainly expect that different evolutionary environments would cause different outcomes. It's also pretty clear that our bodies and brains evolved in a very different environment than the one we now occupy, so there's bound to be some conflict, which causes things like high obesity rates due to overeating, or jealousy and anger being too powerful emotions for anyone's good. Evolutionary psychology is trying to explore that area, and there are some very smart people coming up with interesting ideas.

The problem is that those ideas are very hard to verify. History is replete with smart people coming up with interesting ideas that are widely accepted and also wrong. Pick a common idea from the opposite side of the political spectrum from you, and you'll see what I mean. Just because lots of evolutionary psychology sounds good to me, doesn't mean it's right -- and my concern is that there isn't a good way to validate it.

Unlike climate science, where validation (or invalidation), for skeptics, is certainly coming, in just a decade or two.

[1] The test is cool, actually. There are two versions of the test, which are isomorphic. The puzzle is that only about a quarter of people get the first version right; three quarters of people get the second one right. Do it yourself: test one, test two. Take a look and see what you think -- it'll only take a few seconds.

Done? Most people choose cards 1 and 3 for the first test, though looking at card 3 doesn't prove anything, and you really need to check card 4. On the second test, though, people look at cards 1 and 4. The current theory is that we have evolved neural circuitry for detecting cheaters, and we use that for the second puzzle but not the first.

During patrissimo's blogsplosion today, he approvingly quoted an anti-global-warming post that defined science as falsifiable theories as defined by Karl Popper, and then rejected global warming science on the basis that it doesn't fit Popper's model of science.

There are two problems with that view. The first is that lots of things that we think of as science fit in with Unqualified Reservations' take on climate change, which is that they are observational and not experimental, and models are trained on historical data, and therefore theories can't be experimentally falsified. Here are a few, as I mentioned in a comment to Patri's post:

• Meteorology
  
• Astronomy
  
• String Theory
  
• Evolutionary Biology
  
• Evolutionary Psychology
  
• Geology
  
• Biology
  
• Volcanism
  
• Astrophysics

Actually I could go on for a long time, so I'll just leave that as a sample. Some of those may indeed just be trendy and not good science (string theory comes to mind), but the point is, you can't tell by applying his definition which of these is good science, and which is trendy bad science. Patri tried to argue that evolutionary psychology (not biology, he misspoke) is anti-trendy so it should still count, but really we ought not to be appealing to trends to decide what counts as science.

I think the best example is astrophysics. To get a model of the internal workings of a star, these guys looked only at observed data (it's hard to run experiments on a star and see what happens), trained their models on historical data, used assumptions that are certainly too coarse but seem to work well enough, and yet nobody thinks that isn't science. Further, if the sun does something a little odd, like have an slightly longer-than-usual lull in sunspots, or a weird flare, nobody accuses astrophysicists of bad science or faking their results or whatever. Instead, we all think, "Oh, there's a mystery. I bet they'll figure it out."

The difference is, of course, that nobody is arguing for a big, expensive societal change because of what models of stars predict. You could argue with a straight face that climate science needs to be held to higher standards, because we're making big decisions, but you can't argue it's not science, at least not without throwing out other things you really don't want to throw out.

The bigger problem with Popper is that even experimental science doesn't work the way that he thought. I was all set to write about that, but I realized I already wrote about that. So go read that instead. And realize that, by invoking Popper, you get to throw out any piece of science you don't happen to like, so be skeptical of people who do just that.

My last thought about the claim that the presence of government money is so distorting the climate science field that it's not just getting slightly the wrong answer, but completely the wrong answer, is that I suppose it's possible, maybe... but it really doesn't seem very likely. I know a number of extremely smart people who are working on this stuff, including my father, and I can tell you for sure that those guys don't mess around with changing results for money. I could imagine some of them being a little vague in a grant proposal, but they care deeply about being right, and love to find mistakes and point out bad thinking by others.

From a science funding perspective, note that my father has spent his entire career being funded by oil companies. He worked at one as a post doc, and consulted with them over the years for significant personal money, and was in the department of petroleum engineering until Stanford renamed it because they were doing lots of stuff besides that now. If you want to argue about trends changing the names of the departments, sure, and don't forget to laugh at the Stanford Anthropology Department, which split in half over arguments about the right way to do science. But dad controversially founded Stanford's GCEP with oil company money (and car companies' as well), and his current project is private money, and they are putting together a top team to look at this climate stuff, with no "tainted" federal money (yet). His financial incentives align against global warming, not for it, not that it would impact his research one iota.

So the whole accusation just rings false to me. I'm sure there are lots of papers out there that are just jumping on the bandwagon and aren't doing great science. But I think it is wildly implausible to think that so many talented people are corrupting their life's work to any large degree because it makes it slightly easier to get federal grant dollars. The science world, or at least the part of it I'm exposed to, doesn't work that way. The feds can assure more climate science, definitely. More results in peer reviewed journals that agree with some federal line? I don't think so, not on the kind of scale that it would take to reverse an entire field.

Now that I've managed to convince exactly nobody with this line of reasoning, let me ask you this. Suppose there were a field of science where most people working in the field were honestly pretty sure that the truth was one way, and there was a big movement of politically motivated naysayers accusing them of not being honest. Would the debate look very different than the climate debate does now? I don't think so. Most people get accused of being kooks when they claim a whole field is wrong because most of them are kooks. The same thing is happening with evolution and creationism. If you were to argue that evolution science is trendy and wrong, I would assume you were a religious nutjob and not give you credence. Then you can turn around and claim to be being persecuted for your scientific beliefs and that the whole field is rigged. And people listen to the creationists just like they listen to the climate skeptics.

I don't want to draw that analogy too far; evolution has been on good scientific footing for a century and a half, while climate science is new. I'm sure many, many of the climate details are wrong, just as Darwin was wrong on almost every important or unimportant detail in his theory. It turns out that a good theoretical framework is resilient enough that if you get your details almost right, right enough, that you can come up with the right basic answer. Darwin did it alone in an amazing singular act of genius. Thousands of climate scientists are doing that now without a Darwin to lead them, and it's muddled and contradictory and confusing, but I think the shape of it is right. Right enough that we can and should be making decisions based on the shape of the theory.

What exactly we should do is, of course, unclear. But that's the debate we are starting to have, and that's as it should be.