Over the last year, I've heard a surprising number of people tell me that they don't believe in climate change, and I thought I should check out the other side of the argument more carefully. This book is written by a leading skeptic, who was also one of the founders of Private Eye
, my favourite satirical magazine; if nothing else, I was pretty sure I'd find it entertaining. Although I am, in the terminology of the book, a "warmist", I tried to put aside my preconceptions and read it as objectively as I could.
If you don't want to wade through the whole review, which is quite long, here's a summary. On the positive side, Booker presents a good overview of the skeptical case against the anthropogenic global warming hypothesis. As I'd expected, it's also fun to read; the author is a fine journalist, who writes with passion and humour. He makes some telling points, which deserve careful thought even if you're another warmist. In particular, his criticisms of the large industry that has grown up around renewable energy seem well thought out. But, on the negative side, I am unconvinced by his central claim: increasing levels of CO2 in the atmosphere are not causing global warming. I thought his arguments here were weak and superficial.
While reading the book, I tried to keep three general principles in mind:
- Just because you don't like someone, it doesn't mean they're wrong. Three of the most prominent global warming skeptics in recent years have been George W. Bush, Sarah Palin and Vladimir Putin. I can't stand any of them, and it would be galling to admit they'd got it right. But, on the other hand, Hitler was a hundred times worse than any of these people, and he was right about the dangers of smoking when most of the world was wrong. So personal feelings should be disregarded.
- Just because scientific results are arrived at in dubious ways, it doesn't mean they're necessarily incorrect. What matters is whether they stand up to more careful examination. For example, it turns out that Millikan's oil drop experiment, one of the most famous in the history of science, was fudged. Millikan threw out a lot of anomalous data for no very good reason, and didn't immediately tell his colleagues. But other people were later able to fix the problems and do the experiment cleanly, so really he was right.
- Just because you disagree with someone, you don't need to be rude. In the end, global warming comes down to facts, not opinions. We'll arrive at the truth faster if we argue in a cool and professional way, and I completely agree with Booker that the discussion has become unpleasantly polarized.
So, on to the book itself, which is making the following key claims:
1) The Intergovernmental Panel on Climate Change (IPCC), responsible for providing most of the arguments for the existence of global warming, is primarily a political and not a scientific body, which conducts its business in a dishonest fashion. It has created a climate of hysteria, in which it is no longer possible to question its authority.
2) The scientific evidence for global warming is unconvincing when you examine it closely. It's mainly based on faulty statistical analysis.
3) The political response to the claimed global warming phenomenon has been poorly thought out, and will cause more problems than it solves.
I'll look at these one at a time.1. The IPCC is dishonest
Booker spins a hair-raising story, which describes how the IPCC is run by a small clique of insiders. He says that they systematically manipulate the evidence, browbeat their collaborators into signing off on dubious science, and in some cases even edit the reports after they have been approved by their supposed authors. I have no way of judging to what extent this is true. Since it is very important that the IPCC avoids even the appearance of impropriety, they would do well to respond to these criticisms, and, if necessary, tighten up their procedures accordingly. In particular, if it is true that reports have been edited after contributing authors have signed them, this procedure should obviously be discontinued. 2. Global warming isn't really happening, or isn't being caused by CO2 buildup
So, it's possible that the IPCC have been manipulating the data, but, if they are just guilty of using sloppy methods to reach an essentially correct conclusion, then it doesn't matter much. The key question is whether the global warming hypothesis is correct. I am afraid that I do not find Booker's arguments at all convincing. He makes three particularly important factual claims:
a. The "hockey stick graph" is incorrect.
b. The overall global warming trend reversed in 1999, and the world has actually been getting colder since then.
c. What global warming we have seen has been caused, not by excess levels of CO2, but by the solar sunspot cycle.
So let's look at each of these. 2a. The "hockey stick graph" is incorrect
Booker shows us the famous hockey stick graph, "MBH99", which purports to show that the world was warmer in 1998 than it had been for the previous thousand years.
He quotes people, particularly the statisticians McIntyre and McKitrick, who claim that the methods used to produce the hockey stick are suspect. The problem here is that the arguments on both sides are extremely technical, and the book is not able to present them in enough detail that I can decide for myself who I believe. The problem is a difficult one: consider that we are trying to reconstruct what the average temperature was hundreds of years ago, all over the world, to an accuracy of a tenth of a degree. It is impressive that people agree as well as they do.
There were two high-profile reviews of the hockey stick, one by the US National Academy of Sciences (NAS), and one led by another statistician, Edward Wegman. Both reviews pointed out technical flaws in MBH99. The NAS review concluded that, despite these flaws, the conclusions of MBH99 were substantially correct. Wegman thought that the conclusions were incorrect. Unfortunately, each side accused the other of taking a partisan standpoint.
It seems to me that, even if there are methodological question marks over MBH99, the important thing is that other researchers are roughly in agreement. I've spent some time looking around on the Web. Although the exact shapes of the historical curves vary a lot, they all turn up sharply at the end. There is a nice graphic here, which compares ten such studies.
I can't say I'm 100% convinced, but it seems to me that the burden of proof is on the skeptics. What do they think is the correct graph, and why?2b. The overall global warming trend reversed in 1999
This part of the argument seemed completely wrong to me. Booker cherry-picks his data, and claims that "global warming" was a short-lived phenomenon that only happened between 1970 and 1998. There was, indeed a smooth rise between these two dates, and declines on both sides. However, world temperature varies in an uneven way. If you look at the curve for the whole period where we have recorded data, from 1880 to the present, there is a clear warming trend over a much longer span. I find it significant that Booker does not present a graph of this kind.
His treatment of the melting Arctic ice also seems superficial to me. He makes a great deal out of the fact that there was more ice in 2006 and 2007 than there was in 2005. Small-scale variations like this don't mean anything. Again, if you look at the curve for the whole period where we have data, there is a clear downward trend, even though the curve has many locally uneven portions. And again, Booker doesn't present any curve, just verbal descriptions.2c. It's not CO2, it's sunspots
Everyone agrees that the world was rapidly getting warmer for at least the period 1970-1998 (as noted above, I would say for much longer than that). If it wasn't CO2 causing it, then what was going on? Booker's favoured theory is that it was due to sunspots. The story is interesting, and, looking around, most people seem to agree that it isn't nonsense. High sunspot activity does appear to cause warming on Earth, in part because the Sun is more active then. The big question is how much warming. Again, I notice that Booker doesn't give us a curve. It wasn't at all hard to find one:
Although there is a remarkably good correlation up to about 1975, after that the two curves go their own ways: sunspots went down, but global temperatures went up. The suggested interpretation is that CO2 levels have now become high enough that they override sunspot activity.
In general, I was unconvinced by Booker's case on the scientific part. He is a journalist, and not a scientist, and he talks when he should be showing us numbers. Maybe he just prefers words, but I felt he was also doing it because the numbers weren't the ones he wanted.3. The political response to global warming doesn't make sense
I thought this was the strongest part of the argument. Booker talks sensibly about the way in which politicians have responded to the crisis. He seems to be quite correct in saying that they have not thought through their proposals about renewable energy in a responsible and quantitative way. Variants on "Windfarms good, nuclear bad" are not helping at all, and I liked the way Booker described how unscrupulous entrepreneurs are cashing in on the general confusion. In particular, biofuels seem to have been an embarrassing disaster, and it's less than clear how the sums add up for wind power. I recommend David MacKay's excellent book, Sustainable Energy: Without the Hot Air
, which presents the numbers in a neutral and informative way.
I'm sorry the review is so long, but I feel very strongly about these issues. It's dismaying that the debate has become so polarized, and that everyone is wasting time calling each other names. We shouldn't do that. Where there is doubt about the facts, we should identify the areas of agreement and disagreement, and work to resolve disagreements. All the people involved in the debate have a responsibility to present their view of the situation in as clear and objective a manner as possible.
I think Booker is making some good points here, and, even though I completely disagreed with some of his central arguments, I found his account well worth reading. I encourage people on both sides to try and look at the other side's case in as open-minded a way as possible, so that we can bridge the gap without further delay. Whoever's right, we really need to do this.