Tag Archives: Scientific Certainty

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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Bipolar reporting of scientific certainty

bipolar reporting

Picture my surprise when I read this in the newspaper a couple days ago: “Mini ice age coming in the next 15 years” (Dutch)… It presents the results of the research of Professor Zharkova, who predicts that the activity of the sun will diminish with 60 percent by 2030, which will give rise to a “Maunder minimum” style event with extremely severe winters. She comes to this conclusion on basis of a new and improved model of sun cycles.

The feeling is double. In a way, I am pleased to hear that attention is given to another side. This is a rare occasion where one find a different message than the global warming meme, certainly now in the running up to Paris when the media are hyping scaring stories even more.

However, I am less pleased to notice this makes EXACTLY the same mistakes as global warming reporting. Just look how it starts (translated from Dutch):

We will face a new Little Ice Age in the next fifteen year.

That is putting it with an incredible high level of certainty. There is nothing in that sentence that expresses any kind of doubt or uncertainty. According to the scientist, or interpretated by the reporter, this is what WILL happen. Very comparable with the global warming reporting in which claims are made in no uncertain terms.

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Truly, seriously, scientists can provide a distribution of possible values of climate sensitivity

The last Lewendowsky paper contained quite some statements that made my eybrows lift, just look at the last two posts. Another eyebrow moment was this statement from the seepage article:

We know from earlier work that uncertainty is no cause for inaction-on the contrary, greater scientific uncertainty should make us worry more, not less, about the potential consequences of climate change.

That seem to be a much repeated theme in his work. I saw this previously explained in Uncertainty is not your Friend and even earlier work. The idea behind this is that uncertainty means things could get worse than anticipated.

The reasoning in the “Uncertainty is not your friend”-article is explained like this (my emphasis):

Without going any further, we can already draw one conclusion from this fact: If our best guess of climate sensitivity is 3 degrees, and the uncertainty range is 2-4.5, then things could be worse than expected. We expect 3 degrees but might get 4.5-of course, we could also get as “little” as 2, but we are ignoring the vast majority of possible outcomes if we assume (or hope) that we will “only” get 2 degrees.

So clearly, uncertainty means that things could be worse than anticipated.

But the problem does not end there. There are two additional aspects of uncertainty that we need to consider.

First, we must consider the distribution of climate sensitivity estimates. We know that there is a “best” (mean) estimate, and we know that there is a range of most likely values. But it turns out that climate scientists can do better than that: they can provide a distribution of possible values of climate sensitivity which attaches a probability of occurrence to a range of possible values.


This final consideration concerns the effects of the magnitude of uncertainty. All other things being equal, should we be more worried by greater uncertainty or less worried? If scientists had really down-played uncertainty-as some commentators have insinuated-what would the effects be? What if uncertainty is actually greater than scientists think?

I can understand what he is saying. uncertainty does indeed mean that things could be worse than anticipated. As far as I understand the reasoning is as follows:

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Three quarters of the climate scientists DISagree that climate is chaotic and cannot be predicted

Looking into the climate change matter at both sides, over time it became obvious to me that one of the most important things that are forgotten in the debate is that climate is chaotic in nature and that, with reliable data just since a couple decades, high certainties would be rather unlikely. This had changed my idea from “The scientists know” in my believer years to “How could they possibly be so sure?” now. My idea was that scientists were nevertheless be aware of the complexity, but that it was just difficult to communicate this uncertainty to the public. It was with surprise that I took notice of the Financial Post article: The con in consensus: Climate change consensus among the misinformed is not worth much, with the subtitle “Not only is there no 97 per cent consensus among climate scientists; many misunderstand core issues”.

The 97%-agrees meme and how it is a fabrication was the subject of the article. Two sentences drew my attention. The first was this one:

Like so much else in the climate change debate, one needs to check the numbers. First of all, on what exactly are 97 per cent of experts supposed to agree?

I couldn’t agree more. That is how I see it also. It is also my experience that one has to check the numbers or, more general, what was really said, what was really investigated. It is often brought as if scientists agree that climate change is anthropogenic, dangerous or whatever fits the current story. The problem is that when looking at the methodology of those 97% surveys, one finds that those said statements weren’t investigated at all…

But what really caught me, and this brings us to the title of this post, was this little gem about a recent survey of international climate scientists published by the Netherlands Environmental Agency:

Three quarters of respondents disagreed or strongly disagreed with the statement “Climate is chaotic and cannot be predicted.”

No way! This could not be true… Is it really true? Really?

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