For more posts in this series, please click here.

UPDATE: see updated definition in Footnote #1 below



Appeal to consensus ,” also known as the “bandwagon fallacy,” is an illogical argument that something must be right because it’s popular. For example, “2 + 2 = 4” would still be mathematically true even if everyone believed that the right answer was 5. Other examples of the bandwagon fallacy are less obviously absurd. For example, there is a popular movement afoot these days which claims that vaccines are dangerous. But while the claim is popular, it’s just as illogical as “2 + 2 = 5” – overwhelming scientific evidence has demonstrated that vaccines are far safer than the diseases prevented by the vaccines

People who deny that industrial climate disruption often illogically claim that genuine climate realists (those who respect the scientific data demonstrating industrial climate disruption) are simply joining the climate bandwagon. The error is even more common in discussions about the overwhelming consensus of climate experts and peer-reviewed studies. The problem is that climate disruption deniers are fundamentally misunderstanding and misapplying the bandwagon fallacy.

If a large majority of people accept industrial climate disruption as true because of the evidence, then claiming that industrial climate disruption is true is similarly based on the evidence. The fact that industrial climate disruption is “popular” is inconsequential. The reasons for the consensus matter, as does the expertise of the people who make up the consensus.

In the case of industrial climate disruption there are good reasons to believe that the consensus position1 is correct . There is a massive body of empirical data that describes how the global climate has changed in the past. There are the physical properties of compounds like carbon dioxide and water vapor. There are the many accepted scientific theories that would have to be dramatically wrong for industrial climate disruption to be incorrect. And there are climate models that combine all of the above to project the most likely course of the rest of this century. There is a consensus on industrial climate disruption because the science demonstrates that industrial climate disruption is real. Referring to that consensus is simply a way to refer to the science by proxy.

The expertise of the people who make up a consensus matters too. If someone were to use popular opinion among veterinarians as support for a claim that industrial climate disruption is real, that might well qualify as a bandwagon fallacy. After all, vets in general have no more expertise on the subject of climate disruption than any other educated member of the public. But publishing climate scientists2 are understood to have expertise on the subject of industrial climate disruption simply because they are the people who know the empirical evidence, physical properties, and scientific theories supporting industrial climate disruption the best.

The actual argument would go something like this: “The most knowledgeable people in the world on the subject of climate have overwhelmingly concluded that industrial climate disruption is real, therefore you should too.” This argument is all about expertise, not popularity, and so it’s illogical to label this argument a bandwagon fallacy.

Evidence and expertise matter. And when genuine climate realists refer to the consensus on industrial climate disruption, they’re arguing by proxy that the body of evidence in support of industrial climate disruption is so strong that individuals, businesses, and governments should be factoring it into their decision making. Doing so is the only logically defensible position.

The consensus position is that the climate is changing, that the emission of greenhouse gases by human industry is the dominant driver of those changes, and that the changes will almost certainly be disruptive to human society and global ecology. [italicized section added following discussion in the comments below]

I include scientists who publish papers on climate-related fields of chemistry, geology, physics, optics, et al. For example, an oceanographer with expertise on the carbon cycle in the ocean and thus expert knowledge of the sources of ocean acidification would qualify as a “climate scientist” for the purposes of this discussion. Similarly, a physicist who studies carbon isotopes and publishes about the changing isotopic ratios due to the burning of fossil fuels would also qualify.