Feb 25 2010

Scientific Consensus, Climate Change, and Vaccines

One of the strengths of the skeptical movement, as an intellectual community, is that we wrangle with important issues regarding the relationship between science and what people do and should accept as probably true. We deal with not only specific issues, but the bigger question of process. For example – how much weight should an individual give to any specific scientific consensus, and is this just an argument from authority?

This question has recently become central to the debate over climate change – one of those few scientific debates that fractures the skeptical community. We are fairly united when it comes to the question of ghosts, Bigfoot, and UFOs. But when certain topics come up, like climate change, there is disagreement over the meaning of consensus, what the consensus is, and the very definition of “skeptic”.

Consensus vs Authority

Deferring to the scientific consensus on a given topic is not the same thing as making an argument from authority – a logical fallacy to be avoided. The argument from authority essentially follows the pattern of concluding that a claim is true because it is being made by a person of some authority (scientific or otherwise). Most of us spend our childhood committing this logical fallacy – the right answer is whatever an adult says it is, or the teacher, or whatever the news reports “scientists” are saying.

As we mature and grow in personal knowledge we eventually cross a threshold where we feel confident relying on our own judgment, even to the point of rejecting authority. This seems to be instinctive for teenagers, and of course the rejection of authority simply because it is authority is an overcompensation. Ideally, as adults, we reach an equilibrium where we listen to authority, but understand its limits, and do not use authority as a replacement for independent thought.

As skeptics we have collectively tried to develop a nuanced and sophisticated approach to scientific authority, and many excellent articles have been written on this topic. Since we advocate rigorous and robust scientific methodology as the best way of understanding nature, we trust this process to some degree. We understand there can be fraud or sloppy studies, but generally if the research of others is all pointing toward one answer, we trust that research and its conclusions.

But science is complex, and few people can master more than a fairly narrow range of scientific expertise. And so outside our area of expertise (which is all of science for non-scientists) the best approach to take, in my opinion, is a hybrid approach – first, try to understand what is the consensus of scientific opinion. This is a good starting point – what do scientists believe, what do they agree on, and where is there legitimate controversy? How sure are they of their conclusions, and how strong is the consensus on any particular question?

But also, those interested in science will want to understand the evidence directly and how it relates to the consensus. But at the same time it must be recognized that a non-expert understanding of the evidence is a mere shadow of expert understanding. For example, I have read many articles about Archaeopteryx – a transitional species between theropod dinosaurs and modern birds. I can rattle off some of the anatomical details that mark Archaeopteryx as transitional – the presence of teeth and a long bony tail, for example. But there are details of anatomy that I cannot hope to appreciate, that require months or years of study and apprenticeship, and experience actually examining and describing fossils, of immersing oneself in the literature at the finest level of technical detail. And so ultimately I am trusting experts to interpret the fossil for me – not to mention to reconstruct the bones in the first place. I can only try to understand it on the deepest level I can.

What I conclude from this is that it is extreme hubris to substitute one’s frail non-expert assessment of a detailed scientific discipline for the consensus of opinion of scientific experts.

But there is still more complexity to this issue. First, the consensus of opinion is not always right – it is just usually right. So one can always think that for any particular question this is one of those rare times when the consensus got it wrong. Also, there is almost always a minority opinion among experts – the outlier who is an expert but who constructs the evidence in a different way. So the non-expert can always tell themselves that a particular scientist who is an expert agrees with their opinion. This is not very reassuring, because such minority opinions are in the minority for a reason, and generally turn out to be false. (Although they serve a very useful function in the process of debate and analysis that is science.)

Further, I would argue that there are skill sets that apply, at least to some degree, to just about any science. There is knowledge of scientific methodology and the pitfalls of pathological science. So it is possible to recognize pathological science even in a discipline in which one is not an expert. But even still such out-of-field critiques should be undertaken with extreme caution. The question is – is the criticism dependent upon a detailed technical knowledge of the field, or a recognition that some underlying assumptions and methods are wrong. Even in the latter case, it is good practice to check oneself with an actual expert, to make sure you are not missing something.

I offer as an example the recent criticism of evolutionary theory by non-biologists Fodor and Piattelli-Palmarini. P.Z. Myers explains very well where they went wrong – they make all the mistakes of not respecting a consensus or the limits of their technical knowledge outside their area of expertise.

Climate Change

Getting back to climate change, all of the complexities of assessing consensus are in play. Generally, non-experts tend to accept or reject anthropogenic climate change based upon their politics and world-view. That is a strong indication that most people are not assessing the science objectively, but are simply fitting the science to their ideology.

Don Braman, a faculty member of George Washington University and part of The Cultural Cognition Project, is quoted as saying:

“People tend to conform their factual beliefs to ones that are consistent with their cultural outlook, their world view,” Braman says.

The Cultural Cognition Project has conducted several experiments to back that up.

In the same report, Robert Kennedy Jr. is quoted as saying:

“Ninety-eight percent of the research climatologists in the world say that global warming is real, that its impacts are going to be catastrophic,” he argued. “There are 2 percent who disagree with that. I have a choice of believing the 98 percent or the 2 percent.”

That is a basic statement of acceptance of the scientific consensus. But Robert Kennedy is not always a fan of the scientific consensus – for example he rejects the scientific consensus on vaccines, choosing to believe that the consensus is a deliberate fraud (exactly what global warming dissidents say about the climate change consensus). This makes Robert Kennedy a hypocrite – he accepts the scientific consensus and cites its authority when it suits his politics, and then blithely rejects it  (spinning absurd conspiracy theories that would make Jesse Ventura blush) when it is inconvenient to his politics.

But Kennedy is not alone – this seems to be what most people do most of the time. In fact I would argue that we need to be especially suspicious of our scientific opinions on controversial topics when they conform to our personal ideology (whether political, social, or religious). That is when we need to step back and ask hard questions that challenge the views we want to hold. We also need to make sure that our process is consistent across questions – are we citing the scientific consensus on one issue and rejecting it on another? Are we citing conflicts of interest for researchers whose conclusions we don’t like, and ignoring them for researchers whose conclusions confirm our beliefs?


Being a skeptic is partly about wringing our hands and closely examining these very questions – especially as they pertain to our own beliefs. The question of scientific consensus is complicated, and my views on the topic have evolved over the years as I have discussed the issue with my fellow skeptics and tried to apply it to specific issues. It is an issue worth examining closely.

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