Thursday, January 31, 2008

Bob Carter on Climate Change (Part II)

[Read Part I first!]

It seems that the link Dr. Hunt sent me did not contain parts 2-4 of the lecture. But never fear; I found part 2 on YouTube, so you can watch it there.

In this part, Carter starts off by trying to interpret the temperature trend in the late twentieth century. This makes me a little uneasy because he actually comes out and says that his explanation of the data set as an instance of a step shift is somehow "a much more reasonable interpretation of the data." To illustrate why, it should be noted that an equally plausible claim would be that the trend was flat from 1975 to 1990, and then began to scale upwards in a linear fashion until the present time. But more important is the fact that he's suddenly moved from a time scale of hundreds of thousands of years to a scale of about a quarter century, and is now suddenly interpreting trends, even though he just said that climate trends can't fairly be discussed on such short time scales. To be clear, it's pushing it to say that we can isolate a trend in a century of climate data; it's completely ridiculous to attempt to do so definitively for a time span of three decades, and then say that any other interpretation is flat wrong.

As I feared, Carter's next move is to suggest that the climate has indeed entered a period of "stasis" over the past several years, during a period in which atmospheric levels of CO2 have risen, and therefore the anthropogenic climate change hypothesis has been falsified. Keep in mind that he's just gotten through suggesting that the climate is characterized by extreme levels of natural variability, and that he seems to be implying that it is this variability, and not anthropogenic CO2 emissions, that are responsible for the temperature variations that we've seen over the past century. But if natural variability could be responsible for the entire temperature variation over the twentieth century, why couldn't it be responsible for the recent discrepancies between actual warming and the influence of CO2? That is, why couldn't CO2 be causing the climate to warm, but natural variability be causing the climate to cool, resulting in no trend? I can't think of any reason.

That's not to say that the past several years don't need to be explained. Surely they do. But they shouldn't be taken as proof that anthropogenic climate change isn't happening. They offer no stronger support of skepticism than a decade of warming would offer in support of an anthropogenic climate change hypothesis. And surely if the past decade showed a warming trend, we wouldn't hear that the skeptics had given up. So it just seems like an odd point to try to make. Of course, if the models on which concern about climate change is based predicted warming over the past decade, and there hasn't been any, then it seems like we would have a bigger problem. But I haven't heard anything like that, and Carter isn't saying it, so I'd suspect that it hasn't happened. And if it hasn't happened, then it's likely that it wasn't really contrary to mainstream expectations at all.

That, of course, shouldn't be taken as proof against Carter. But it certainly raises the question why, in a time period in which the IPCC has been working on its latest report which has just recently been released, was no one making a huge deal about this issue? Why is some geologist from Australia the first one to bring it up? It seems much more likely that it's because it's not an issue than that it simply never occurred to anyone.

Carter's next point is, essentially, that some Australian scientist guy doesn't believe that climate change is occurring, that a committee of some sort potentially overstepped its boundaries by making statements it wasn't qualified to make, and that most people who talk about climate change don't know what they're talking about. I honestly see no reason to object to any of these claims, but I'll point out that they have absolutely nothing to do with anything, and certainly aren't a "torpedo" against the mainstream view.

He moves on to say that governments around the world have agreed that "the Alarmist case does not stack up." And this is true, except that the "Alarmists" those governments are talking about are the ones predicting certain doom and catastrophe, while Carter seems to be implying that anyone concerned about climate change is an alarmist. This isn't fair, but it's a rather minor point anyway.

Carter ends the section by comparing the mainstream opinion to a religion. Given what he's said so far, I think it's fair to say that he either hasn't read the IPCC's reports, or is intentionally misrepresenting them. The fact of the matter is that the science is available for anyone to see. The reason that people like Carter get shouted down is that they misrepresent the science and convince people of things that aren't supportable, even with the data that Carter uses. But more importantly, people like Carter get shouted down because the people who could explain why they're wrong are too busy to deal with people like Carter. Just look at how much time I've just spent critiquing 17 or so minutes of Carter's speech. It's simply not worth it for a reputable climate scientist to go through this every time a Bob Carter comes around spouting a bunch of nonsense.

But I'll forge on to the next section; hopefully things get better and not worse...

[Go on to Part III]


Anonymous said...

What you didn't mention is that Professor Carter notes that short trends he talks about are statistically insignificant. Those are the same short trends that AGW proponents are using to make their case.

Danny Shahar said...

Well I recognize that he claims that to be true, but that's not the same as it actually being true. The mainstream opinion on this issue is that the trends are not statistically insignificant, and Carter does not provide any good reason to back up his claim.

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