Sugar versus fat: why so many scientists got it so wrong for so long

Looking for more background when I was writing previous post, I came across a very lengthy, but nevertheless interesting story in The Guardian. This long read is titled The sugar conspiracy and the subject is the battle between the theory that sugar is the (main) reason for the obesity epidemic and the established theory that fat was the culprit.

This is not something recent, the controversy originated already in the middle of last century and, although the fats theory was found to be ultimately wrong, the sugar theory was ridiculed, discredited and careers were ruined. It took fifty years for the theory to resurface, leaving the question why the top nutrition scientists got is so wrong for so long.

We hear that objection often in climate change discussions: so many scientists can’t be wrong for so long. Well, it is possible and the sugar theory is only one of its manifestations.

The most interesting part of the Guardian story is the tension between the scientist who first proposed this theory (John Yudkin) and his scientific adversary (Ancel Keys). It reads like the current controversy on climate change. Replace Yudkin with your favorite skeptic, Keys with your favorite alarmist, fats with CO₂, meat/dairy/sugar industry with Big Oil/Tobacco and the story sounds really modern. There are a lot of similarities between how the scientists in the two sciences treat those who are skeptical towards the consensus position.

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More about observational and experimental science

Looking at the stats pages of my WordPress account, I found quite some views suddenly coming from reddit, more specifically from the thread The Observational science that is mistaken for an Experimental science, where some quotes from my previous post with the same title were discussed. I don’t see how to react there (and I don’t even know if I want to, looking at the style of reactions), but the reactions are rather typical, so some more context could give better understanding.

[Quoted from my post]
The problem is that it takes experimental research to determine cause and effect.

[Comment on this quote]
This is simply not true. Cause and effect can be determined from first principles (Such as increasing radiative forcing will make it warmer), inferred from observations (Thunder is caused by lightning) or form part of a theory that is proven by other means (gravitation affects light because it is a curved space-time phenomenon)

The Observational science that is mistaken for an Experimental science

In my weekly catching us with the news I came across this article: Why the environmental movement can let the GMO-dossier go. In it, an environmental activist writes about how he changed his mind over genetically modified organisms. Before, he campaigned against them, but after looking into the matter, he changed his mind.

That is all very praiseworthy of course, but it was the way he changed his mind that surprised me (Translated from Dutch):

I decided to do the same as environmental movement relating to global warming: look if a scientific consensus exists that is based on the most reliable scientific studies such as systematic reviews and meta-analyses published in leading peer reviewed top journals like Nature and Science.

When he found there was a consensus that there are no indications that GMOs are harmful, he changed his position. The rest of the text was about further exploring this consensus position.

This was strange to me, because he seemed to be an intelligent guy with several university degrees, yet when he wanted to investigate an issue, he based it solely on the consensus position…

I have been there also, so I realize that of course it is not entirely illogical. When a group of scientists (who have it as their job to study a certain issue and therefor are experts in their field) agree on something, then it is not difficult to see that other people (who didn’t study it that closely) have no reason to doubt such a consensus. Whether we believe a “scientific consensus” is meaningful or not. How could those who didn’t study the issue as closely as the experts, criticize this consensus?

It is not really unreasonable to agree that a consensus is the accepted view with our best current understanding and the best starting point when we try to grasp a new field of study. In a way, I still hold this view, still today. If I am told by the experts that the consensus is that earth circles around the sun or that gravity exists, as a non-expert I have no problem with that and the consensus would be a no-brainer. Legitimate authority matters.

So why would I think differently when it comes to climate science?

Observational science versus Experimental science

We often hear the claim that the debate is over, that human activity (CO₂) is responsible for changing the climate, that there is overwhelming evidence to prove this. But can this level of certainty in attribution really be achieved in climate science? As far as I know climate science is an “observational” science. This kind of science is being done through the observation of nature just taking its course and recording the findings over time. As opposed to the “experimental” sciences that advance via controlled experiments.

There are other observational sciences like geology, social sciences, epidemiology and so on. All those sciences can not perform controlled experiments because it would not be ethical or it would be impossible to do. For example, in astronomy it would not be possible to manipulate stars or galaxies in order to observe what happens when the researcher changes something. Or in medical observational science it would not be ethical to administer one group with a medicine, while another group gets only a placebo.

In climate science there is only one test subject: Earth. We don’t have the luxury of three similar planets in which we extract CO₂ from one, add CO₂ to the other and compare that to our Earth. Therefor there is no other option than to observe what is happening and record the findings.

Observational sciences have their limitations. Observing nature taking its course means there are many variables involved and in the research only one (or a few) are accounted for. To pinpoint one cause, and only one, it is necessary to isolate that factor and change that while keeping other factors the same. Then if there is a change in output, one could be sure that this is because of this one factor that was changed. That is what experimental science does and that is the difference with observational science.