There’s a common statement made by people on both sides of the global warming/climate change debate. It goes something like this
Science isn’t about belief, it’s about evidence.
The basic argument is that you don't believe the science, you consider the evidence. The evidence tells you whether or not a particular scientific idea has merit. There is, however, a subtlety to this that people either don't realise or don't want to acknowledge. You may not believe the actual science, but you do believe in (or trust) the scientific method.
So, what do I mean by this? The scientific method is the basic idea that science progresses through ideas being tested and verified by many different people/groups in many different countries and at many different times. Eventually there's an acceptance that a particular bit of science is robust and that we can trust the results that have been obtained. We can then use the results of the research in other areas of science or to do new science. However, people who use what I'll call accepted science often never go and personally check that the earlier results are correct. They trust that the scientific method has worked and that these results are robust. This is perfectly reasonable. If we have to double check every bit of science that we need to use to do our research, we’d never get anything done.
That’s not to say that, as a scientists, you’re never exposed directly to the research that’s been done before. As a physics undergraduate, you’ll typically do experiments to – for example – measure acceleration due to gravity, measure the charge to mass ratio on an electron, quantify crystal diffraction, measure radioactive decay. This type of undergraduate laboratory work may help to confirm some basic science, but it’s not really why it’s done. It’s more to teach students about the experimental method, about data analysis, and about uncertainties. We also observe things in every day life that are consistent with our current scientific understanding. The sky is blue because of Rayleigh scattering. Gravity attracts us to the Earth, but planes that do parabolic flights can simulate weightlessness. Planes actually fly, which confirms the Bernoulli principle. Footballs curve if you put some spin on them. So, if there were fundamental problems with our current scientific understanding of the world, we would probably notice, but it’s still true that much of what we use today we haven’t personally verified. We’ve trusted the scientific method.
One reason I was thinking about this was that I was being challenged on Twitter last night to not only explain what science I had read, but to also to engage in a discussion about criticisms of the hockey stick reconstructions. Firstly, I was trying to watch a movie and also had really had too much wine to drink to seriously engage in either discussion. I also, however, find both “challenges” a little strange. What am I meant to say to someone who asks me to explain what science I’ve read? I’ve read a lot in many different places. I understand the atmospheric greenhouse effect. I’ve checked how the forcing due to CO2 varies with changing atmospheric CO2 concentrations. I’ve read papers about the influence of the Sun (by Mike Lockwood for example). I’ve read papers on climate sensitivity (Nic Lewis and Otto et al. for example). I’ve read papers about the change in ocean heat content (Balmaseda et al., Loeb et al., Nuccitelli et al.). I’ve read some paleo-climatological papers (Mann et al. and others). I’ve read papers about Arctic sea ice and changes in sea level.
What do I conclude? I conclude that equilibrium climate sensitivity is likely to exceed 2oC. This means that it’s likely that we will have locked in at least 2 degrees of warming by the mid 21st century. I conclude that sea levels are likely to rise by around 0.5m by the end of the 21st century. I conclude that what we’re currently undergoing is unprecedented in the last 1000 years and that soon the Earth may be warmer than it’s been in all of human history. I do, however, understand some of the underlying physics well and have done some calculations of my own to check various things (which you can find if you read some of my others posts), but I clearly haven’t checked all of this in great detail. It’s not possible to do so. I’ve had to trust that the scientific method is working. Maybe it’s not. Maybe there’s a massive conspiracy. Maybe this whole edifice will come tumbling down. That would, however, be remarkable. How can thousands of scientists across the world maintain such a conspiracy without it being obvious that it exists? Personally, I’m going to trust the scientific method rather than assume some incredible – and highly unlikely – conspiracy.
So, why didn’t I really want to engage in a discussion with someone about criticisms of hockey stick reconstructions. One obvious reason is that I probably know what they’re going to say and they probably know what I’m going to say. It’ll be one of those rather pointless discussions that goes nowhere. The more fundamental reason, though, is that if there are significant criticisms that would change the results of hockey stick reconstructions, this should be published. That’s how science works. You don’t simply find errors in a piece of work. You have to show how this error influences the result. Until someone publishes a reconstruction that is significantly different to those published today, and until such reconstructions have been verified and confirmed, I’m going to trust the scientific method, not someone on a social network who, as far as I can tell, has never published a scientific paper. I also, to be honest, find it quite arrogant; listen to me, I know better than thousands of experienced, qualified scientists. That may sound ironic coming from someone writing a blog about climate science, but I’m not insisting that you listen to me and I’m not going to judge you if you choose not to.
I did, however, have a very interesting discussion with Tamsin Edwards about using Bayesian methods to do paleo-climatological reconstructions. Her argument was (I think) that we could use Bayesian methods to introduce more detailed/complex climate-proxy models. Her argument, though, wasn’t that the current statistical methods were fundamentally wrong. It was simply that applying a different method would be valuable, and I completely agree. Tamsin did argue that the Bayesian method would introduce additional uncertainties and, hence, that current methods may be under-estimating the uncertainty. This may well be true, but doesn’t make them “wrong”.
I should make it clear that I’m not suggesting that everything is settled. Simply that the evidence within the scientific literature is pointing in a consistent direction. We are likely to undergo continued warming and will likely see increased surface temperatures, reduced Arctic sea ice and increased sea levels. Past climate history tells us that our future climate is likely to be unlike anything we as a species have experienced before. I’m also not even suggesting that the criticisms that some aim at some climate science research has no merit. I’m simply suggesting that if it is significant someone should publish new work that illustrates what impact these “errors” have on the results. That’s how the scientific method works and until someone can convince me that the scientific method is not working in the case of climate science, I’m going to – unapologetically – continue trusting it over a bunch of largely unpublished critics.