About that “97% of climate scientists…” thing you keep hearing

We’ve all heard that “97% of scientists agree humans are destroying the planet.” But things get interesting when you consider the source of that claim instead of merely trusting all those people who blindly repeat it.

That source, by the way, is right here, at this link. So let’s dive in and examine it.

I was recently inspired to look into this because of an article I read this website. I know the author; he’s a good guy and I respect him. We just don’t see eye-to-eye on some issues. I also recently stumbled upon a couple of interesting videos on this subject, one of which is below.

The 97% study was conducted in 2013 and its rapid acceptance is interesting on its own. Seemingly overnight “everybody knows” that 97% of scientists agree that we’re destroying the planet. Are there problems with this claim? Let’s start with some low-hanging fruit.

First, scientists are human too. They are prone to bias, just as much as the fellow in the video above. Just as much as you and I. They are also prone to group-think; going along with what “everybody knows.” And considering they have to get their funding from external sources it should be expected that at least some of them will toe the party line to keep their funding secure, even if they have to choose not to ask certain questions, or examine certain data. It’s not deceptive, technically, it’s just beneficial for their retirement plans. After all, we’ve seen what happens to those who dare to question what “everybody knows.”

And let’s not overlook the fact that people tend to choose career paths that interest them. People probably get into climate science at least in part out of a desire to make a real difference. To what extent is selection bias at work here? It seems entirely plausible that at least some scientists enter the field of climate study because they are concerned about AGW (Anthropogenic Global Warming) and, lo and behold, they find the data in their studies to support their preconceived ideas. This isn’t a swipe against those scientists, just an acknowledgement that they are human too. We are all susceptible to this. And with so much end-of-the-world talk surrounding this issue there must be immense pressure in that field to confirm the theory that the sky is falling. After all, who wants to be labelled a “denier” and start putting humanity at risk?

So, what about the study?

Ok, that was just some low-hanging fruit, and now we get into the really interesting stuff. Not surprisingly (for those who know me) I just had to dive into their data and examine the numbers for myself. As an aside, I would encourage everybody to get into this habit. It’s remarkable what you can learn when you read scientific studies instead of simply reading the news articles, or social media memes, that attempt to distill them down for mass consumption. Invariably something always gets lost in translation.

[The raw data behind the study is here, and is easily imported into Excel.]

First, it must be pointed out that this was not a survey of climate scientists, per se, but a reading of paper abstracts on a wide range of published papers related to climate change. At best this study can claim that “97% of climate study paper abstracts support AGW” as opposed to “97% of scientists…”

Unfortunately, it cannot even make that claim, as the paper itself makes clear. The majority of the studies discuss climate change without necessarily saying anything explicit or implicit about whether human activity is a factor. They leave the question of AGW completely untouched. So we’ll have to narrow this down even further and clarity that, “97% of climate study paper abstracts that address AGW support AGW.”

But it gets even more interesting than that. They included not only papers that directly address AGW, but even those that indirectly address it; papers that do no more than merely imply a connection between human activity and climate change. That’s right, they didn’t limit themselves those papers that explicitly stated that humans are wrecking the planet, they even included papers that merely implied human activity is at fault. So, at best, this study concludes, “97% of climate study paper abstracts that discuss AGW, support AGW either explicitly or implicitly.”

One should naturally ask what the breakdown is with respect to each level of endorsement. Do more papers explicitly endorse it, or do more implicitly endorse it? The authors break down a paper’s endorsement into 7 categories:

  1. Explicitly endorses and quantifies AGW as 50+%
  2. Explicitly endorses but does not quantify or minimise
  3. Implicitly endorses AGW without minimising it
  4. No Position
  5. Implicitly minimizes/rejects AGW
  6. Explicitly minimizes/rejects AGW but does not quantify
  7. Explicitly minimizes/rejects AGW as less than 50%

Any guesses as to what percent of the papers they looked at fall into the first category? 0.54%. Yes, you read that right; less than 1% of papers that specifically address the subject of climate change explicitly endorse AGW. Remember, these are papers that specifically deal with the subject of climate change, not just random scientific papers on any old subject. Despite the fact that all of these papers were specifically selected because they examine the subject that seems to be on everybody’s mind, less than 1% of those papers clearly and explicitly point the finger at human activity as the primary driving force.

Ok, let’s broaden that out a bit. How about the first two categories; the two categories that explicitly support AGW, but with varying levels of enthusiasm? The second category agrees that humans are contributing to climate change, but these papers do not specifically say it is primarily our fault. To the 0.54% you can add another 7.72% of studies that endorse AGW but did not estimate the extent to which human activity was a factor; a total of 8.26% of these studies explicitly endorse AGW to varying degrees. Less than 1 in 10. Which means 91.74% of climate studies are either silent on the issue of AGW, or they reject it, or they merely “imply” support for AGW.

And if we recognize that only the first category – that’s the 0.54% of climate studies – actually puts any quantification on the impact of human activity on climate change (i.e. it’s mostly our fault!) then we have to admit that 99.46% of climate studies are silent with respect to whether or not human activity is the primary driving force. Some of those studies reject such a conclusion, I might add. Most are simply silent.

What’s even more interesting (in my opinion) is how the authors of the study tallied the “explicit” and “implicit” numbers together. There is a pragmatic reason for doing this; vastly more studies limited themselves to “implicit” than were ever bold enough to declare an “explicit” endorsement. 24.36% of the studies merely imply AGW, whereas only 0.54% strongly and explicitly support AGW.

Here’s how I would break down the results:

66.73% of studies are silent on the issue of AGW.

24.82% of the studies “imply” a conclusion on the issue of AGW (either support or reject).

8.46% of the studies explicitly declare a conclusion on the issue of AGW (either support or reject).

Now, to be fair, for those studies that imply, or explicitly endorse, a conclusion regarding AGW, clearly those studies are overwhelmingly on the side of supporting it. See above points regarding selection bias and funding sources for some context on that admission.

There are so many ways to slice and dice the data in this study, but it seems to me that cantilevering out from the actual data to the conclusion that “97% of climate scientists agree…” is a blatant misrepresentation of the highest order.

I’ll leave the final word to Homer Simpson…