The two faces of consensus


When searching for information to be used in previous post I found an article in about risk, emotion and global warming. Reading it, I was catapulted back to my alarmist years. It gave an accurate insight in how I was thinking only five years or so ago. It started like this:

I am not going to lie to you; I am freaked out about climate change. At least politicians today can say something to the effect of “it’s something that the next generation must face down,” seemingly abdicating their own responsibility. But I am a part of that next generation. Climate change is something that I am going to have to deal with, and I’m not sure if my generation and I can.


Moving forward I am going to assume two things. First, that global warming is happening and is human caused (as per the scientific consensus), and second, that most projections about the effects of climate change are grim. That is to say, whatever comes of climate change, it won’t be good. […]

I don’t want to throw stones at anyone. I realized that just about five years ago I was thinking exactly the same things. I can clearly feel his pain. Maybe freaking out would be a rather strong term, but at that time I found the changing climate (then mostly called “global warming”) worrying.

I also assumed that climate change was happening and that our future looked grim if nothing was done quick. This was rooted in my, at that time, unshakable belief in the scientists and the models they used. I also thought they exaggerated their findings, but that they were nevertheless correct.

At the base of it all was “the consensus”. I had other priorities and believing in a broad agreement between scientist was really reassuring. I didn’t had to check anything, didn’t need to think for myself. Just believe what was being told.

To be honest, I have no real problem with the consensus as a concept. It is an agreement of a group of scientists and therefor I can agree that in a field that was studied extensively such an agreement could exist. But I know that there is not something as a “scientific consensus”. As Einstein once said: “There only have to be one to prove me wrong”. The consensus is not part of the scientific method, nor does the consensus prove anything. To believe that the consensus is right, it is necessary to also believe that there is conclusive evidence. It is just a logical fallacy to claim that there is conclusive evidence because there is a consensus between “experts”. There is not much value in arguing about whether there is a consensus or that the consensus proves something.

I do have a problem with a consensus specific in climate science. This for several reasons.

Climate science is a rather young science and only since the last three decades detailed information was gathered. Climate is weather over a longer timespan. 30 years is only about half of a cycle. Before that there was only sparse data, not intended to use as a tool for measuring global temperatures and therefor the data is prone to interpretation. Just look at the ever changing Giss dataset.

More, how in the world can there exist a consensus in a science consisting of multidisciplinary fields studying a complex, chaotic system and sparse historical data available? The uncertainty should be high. Increasing uncertainty (for example about the role of CO2) is more likely to decrease agreement.

There is also another dimension: consensus can be used to stifle debate, close out opponents with another vision or with challenging viewpoints. It is an often heard message: “the debate is over”. If the consensus is about avoiding talking about the evidence it is also just a logical fallacy.

Last, but not least, what is the value of a consensus in a group of scientists that was selected by politicians with a special goal?

Apparently my view on the issue changed quite a lot during the last years and I found myself on the other side of the debate. That doesn’t put me in the most comfortable position, but I think this was the right way to do. Just taking things for granted undoubtedly did put me in a comfortable position, but this can’t compare with the insights gained when looking at both sides of the issue.


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