Yesterday I pointed out that Drew Ryun, like his father, is less willing to consider the science of global warming than Newt Gingrich, of all people. He responds today without actually linking to me, a violation of ‘netiquette which is unfortunate for his readers, especially since he seems to misquote me. It’s worth looking at what he says to improve how we understand science in general, and climate science in particular. He claims:
It is the tactic of the global warming crowd to run around and say, “Look at the consensus of the science community! Global warming is a fact!!” Again, I know it’s the politically correct rage to do so, but let’s look at other scientists who disagree with the politically correct crowd. I guess Richard S. Lindzen of MIT wasn’t a good enough source, and according to some, the “only scientist” who agrees with me.
I note only in passing that I didn’t say “only,” I said that Ryun “was able to find one scientist who isn’t so sure” about climate change. Having read widely about this issue for over a decade, I don’t doubt that he could unearth a couple dozen people who would disagree with the consensus reached by thousands of experts and embodied in the IPCC reports. But this, like his initial appeal to the authority of “MIT (one of the ivory tower of ivory tower bastians [sic] of academia),” is of limited value. This, like all science, isn’t about personal opinion.
Science is sometimes presented as some generic form of expertise. Creationists love to trot out engineers or other people with letters after their names, but without any actual understanding of what they are talking about. Science is a process for evaluating certain claims using certain sorts of evidence. Anyone can do that, and anyone can check how other people did it.
The question is not whether Dr. Lindzen or Allegre disagrees with the consensus as represented by the IPCC, the NAS, the peer-reviewed literature, etc. The question is what evidence they (and those closer to the consensus views) have for those claims. Allegre cites increasing Antarctic ice, despite the fact that models of anthropogenic climate change predict exactly that. Models of the climate that do not account for human activities do not capture real dynamics that we have observed. I don’t care what Dr. Allegre’s CV says, his argument isn’t convincing.
Dr. Lindzen complains that “[m]any of the most alarming studies rely on long-range predictions using inherently untrustworthy climate models.” Even if we grant his claim about the reliability of the models (and I don’t), the nature of any model is that the error could just as much be towards greater temperature increases than towards smaller ones. It is a fairly trivial error to make, wishful thinking of the worst sort, to ignore what the models say, and to consider only the possibility that everything will be fine.
I point out these reasons why I reject these criticisms for two reasons. First, because Lindzen is one of the most prolific climate change deniers, and it’s worth responding to him, at least briefly. Second, because it illustrates the way that anyone, scientist or not, ought to approach claims made by scientists in the popular press. The issue is not someone’s pedigree, but the quality of the argument. Had I simply brought out NASA’s chief climate scientist or the Louis Block Professor in Geophysical Sciences at the University of Chicago to “balance” Lindzen or Allegre, I would simply have left you, the reader, wondering which named professorship was more credible.
That’s not how science works. Here’s how it works.
The average temperature of the planet has risen in recent history. We can trace that from thermometers placed around the world, and from other data, as the IPCC report explains:
Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level.
No one at this point, not Allegre or Lindzen, not anyone, argues that that trend isn’t there. To the extent we know anything with certainty, we know that there has been a general warming of the planet. Some areas did get cooler, but that doesn’t mean the trend doesn’t exist. Loaded dice are still capable of landing on all faces, some are just more likely. The dice for global climate are obviously loaded. The question is by what.
Even before the temperature trend was obvious, we knew humans were adding carbon dioxide to the atmosphere. One of the coolest scientific graphs is the one shown here, showing the seasonal and long term trends in atmospheric carbon dioxide concentrations. Since 1958, researchers have measured the air at an observatory on Mauna Loa, far from factories or other sources of carbon dioxide. Each year, as the forests grow leaves, they take carbon out of the atmosphere, and as the leaves fall and decay, it is released again. Beyond those annual cycles, there’s a fairly obvious trend, and it isn’t hard to figure out why: human combustion of fossil fuels. There are ways to test that hypothesis, too, but let’s skip the isotopes for now.
We also know, based on laboratory measurements and the basic principles of physics, that carbon dioxide absorbs light and converts it to heat, roughly the way glass in a car window (or a greenhouse) does.
The earth’s atmosphere isn’t simple, and we wouldn’t expect the effects of adding a warming agent to the atmosphere to be simple, either. But when you add a warming agent, and get warming, the first culprit to explain that warming has to be that agent. Especially when the sun’s intensity – the other suspect offered by lots of deniers – hasn’t got a long term trend over the relevant time scales.
That intuition gives us a hypothesis, one we can test. By building models of the global climate, we can estimate how our actions might alter climate. Those models predict the general pattern of warming, and they even predict that some areas might get cooler, and that snowfall would increase in some parts of Antarctica. As the figure shows, leaving out human effects fails to predict the actual changes we’ve seen. In the first figure, the real data (red) goes up, while the model goes down. When human actions are accounted for, the two lines overlap. On that basis, I don’t have any reason to doubt that the addition of carbon dioxide (along with methane and other heating gases) has contributed to the warming we’ve seen, and will continue to do so.
I should point out that Lindzen and his ilk will sometimes pose a very different standard. In the article Drew Ryun quoted, Lindzen wrote about what would happen “if emissions were the sole cause of the recent temperature rise,” a different issue than what the IPCC talks about, which is that “Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.” There’s a difference between being the “sole cause” and causing “most of” the warming.
Scientists rarely talk in terms of absolute certainties or exclusive causation. Science isn’t about absolute statements, just about paring the possible range of truths down to a more manageable few. The IPCC reports represent that uncertainty by using phrases like “very likely” to signify their estimate that it is better than a 90% chance of that being true. Appreciating the state of uncertainty and interpreting it is something which requires a detailed understanding of the available data, an assessment best made by experts in the field. In that setting, the question is how to pick that expert.
Drew Ryun seems to be choosing his experts by finding which ones agree with what he wishes (or believes) were the case. As a non-scientist, he knows he can’t assess the evidence itself, and he has to trust someone. As a scientist with training in some of these issues, I can evaluate some of the claims on my own, but even I have to rely on experts. It gets me nothing to choose my experts in a biased way, I would rather find the scientist(s) most likely to be right. Within the range of existing scientific opinion and evaluation, most of the views are likely to cluster around a certain point, based on their expert knowledge of the evidence. That point may not represent the true state of affairs, but it is the view that is most likely to be right. Choosing an extreme that I agree with is no more reasonable than choosing the opposite