This article is from a year ago, but it was just sent to me as it is making the rounds in climate change denying circles. It is by Paul Macrae, who is an ex-journalist who now seems to be primarily engaged in climate change denial. The article (a chapter from his book on the subject) is full of the standard climate denial tropes – for the sake of space, I would like to focus on three specific points. The first is the claim that climate science is “settled”, the second is the notion of “post-normal science”, and the third is a factual claim about the accuracy of prior climate models.

Of course, if there is a consensus among climate scientists that global warming (I will get into more details on what this means) is “settled”, that makes it difficult, especially for  a non-scientists, to question the conclusion. So order number one – deny that there is a consensus, deny that consensus is even a thing in science, and deny that science can ever be settled.  I don’t suspect that I will ever be able to slay this dragon, it is simply too useful rhetorically, but for those who are open to argument, here is my analysis.

First – consensus is absolutely a thing in the regular operations of science. A consensus can be built in a number of ways, but often panels of recognized world experts are assembled to review all existing scientific data and make a consensus statement about what the data shows. This is often done when there is a policy or practice question. For example, in medicine, practitioners need to know how to practice, and these consensus statements are used as practice guidelines. They also set the standard of care, so as a practitioner you should definitely be aware of them and not violate them unless you have a good reason. Obviously, the question of global warming is a serious policy question, and so providing scientific guidance to policy makers is the point, such as with the IPCC. Consensus is also used to set research and funding priorities, to establish terminology, and resolve controversies. But to be clear – these mechanisms of consensus do not determine what the science says. That is determined by the actual science. The point is to provide clarity regarding complex scientific evidence, especially when a practice or policy is at issue.

The reason we need such expert review is because scientific evidence, as regular readers here know, is complicated. Science is not a simple matter of proof. There are many different kinds of evidence – observational, experimental, theoretical, and modeling (computer modeling, animal models, etc.). Scientific evidence can use deduction, induction, can start with observation or start with a hypothesis, can use theoretical constructs, can make observations about the past and make predictions about the future. All of these various activities are part of the regular operation of science. No one type of evidence is supreme or perfect – they all represent different tradeoffs. Scientific conclusions are always a matter of inference – scientists make the best inference they can to the most probable explanation given all of the available evidence. This always involves judgement, and some opinion. How are different kinds of evidence weighted when they appear to conflict?

So it is a meaningful question to ask – to different scientists looking at the same question from different perspectives come to roughly the same conclusion? For example, do those doing ice-core analysis large agree with those looking at tree rings? We have data from different kinds of temperature measurement, from physicists looking at the activity and influence of the sun, and the role of CO2 as a greenhouse gas. We may even have data from planetary astronomers. Then we have various computer models, which take input from many sources of information. No one source of information is definitive. So scientists triangulate from different perspectives and see if they align on the same answer. The only way to know is to see if there is a consensus among the various scientists, each with different pieces to this enormous puzzle.

But of course, in order to be precise, you have to break down the question of global warming into it’s specific pieces – does CO2 drive warming, are there other sources of climate forcing, what is the climate sensitivity to CO2, is the planet actually warming and how much, and what will be the consequences of different levels of warming? We can’t just say – climate change or global warming, we have to address each component separately.

Is science ever “settled”. Macrae conflates this notion with “certain” (there are such straw men throughout his article). Science is never 100% certain, and it is never done. But there is a place for the notion that some claims in science are so well-established that they are functionally settled, meaning we no longer have to specifically establish them over and over again. We can take them as a given and move on to more detail and other sub-questions. For example, it is settled that the Earth is roughly a sphere, while planetary scientists continue to revise greater and greater detail. It is established that life on Earth is the result of organic evolution from a common ancestor, that the brain is the organ of the mind, that DNA is the molecule of inheritance, that plate tectonics is real, and that multiple sclerosis is an auto-immune inflammatory disease. Research in all these areas is ongoing, but there is very strong agreement (a consensus) that these basic fundamental questions are settled.

They could still, theoretically, be overturned, but the probability is so close to zero we can treat it functionally as zero. It is simple not a serious scientific possibility that the Earth is flat, that life was created 10,000 years ago, that consciousness lives in the heart, that proteins carry inheritance, that the Earth is completely static, or that MS is caused by an imbalance of the humors. Would Macrae agree that any of these questions are scientifically “settled”? Should we give serious consideration to flat-Earthers?

With regard to climate change, it is well-established (use whatever phrase you like) that CO2 is a greenhouse gas, and that the planet is warming. It is also well-established that industrial release of previously sequestered CO2 into the atmosphere and therefore the carbon cycle is forcing the climate to become warmer on average. There is a range of possible climate sensitivity, which is open to revision, but that range has statistical confidence intervals and the range is narrowing as our confidence increases through further research. Exactly how much warming will occur is open to further study and revision, but again there is a range with confidence intervals. What will the consequences be? This is difficult to predict, but there are some very reasonable statements that we can make, informed by climate models and what has already happened over the last 30 years. But there is a lot of uncertainty – and of course, that uncertainty cuts both ways. It could be better than the average prediction, or it could be worse.

What is not reasonable is to assume everything will be fine. This is like facing the possibility of cancer, with the same degree of uncertainty. Just hoping that it’s all fine and doing nothing is likely not a rational course of action. This doesn’t mean you have to opt for the most radical surgery either. There is often a range of options, which can be determined by the level of evidence and the resulting risks vs benefit. Doing nothing about climate change until we have a high degree of certainty is also not a rational course, because climate change gets harder and harder to deal with the longer it goes and the worse it gets. Solutions also take decades to unfold.

Typically, those in the denier camp use the most unreasonable or extreme version of climate mitigation strategies as if they are the only option. This is like alternative medicine proponents characterizing all cancer treatment as “cut, burn, and poison.” Macrae similarly writes:

“And shouldn’t we be especially wary when this science, with its attack on fossil fuels, threatens the very foundations of Western-style civilization?”

Now who’s the alarmist? Sure, there are extremists on the fringe of every movement. In terms of actual proposed policy, however, and the center of gravity of climate discussion, we are mostly talking about investing in R&D, investing in infrastructure, and jiggering the markets away from fossil fuels and towards green energy. There is no serious policy discussion about banning fossil fuels and collapsing western civilization. There is nothing like that in the Paris Accords, or in any UN recommendation. Whatever you think about the effectiveness of Biden’s policies, they were entirely carrots for industry to increase investment in green energy. About the most radical actual policy proposal is a carbon tax, which most economists agree would likely be effective. This would hardly collapse civilization.

These are all inevitable technologies because they are superior to burning fossil fuels on many levels – cleaner air, reduced health care costs, more energy independence. We just want to make them happen faster.

Tomorrow I will write part II, covering post-normal science and the accuracy of climate models.