Why the need to declare a consensus?

When learning about the methodology of the Cook Survey, one question kept on popping up: why the need to declare a consensus in a scientific paper?

It doesn’t seem to make much sense scientifically. Science is not advanced by consensus. There is no showing hands or headcount. Also, logically it doesn’t matter how many scientists have the same opinion. Even if 100% of the scientists have the same opinion about something, that doesn’t make it more true. This made me think about what Einstein once said when he heard that 200 scientists signed a letter stating his findings were considered faulty. He wasn’t really impressed by the sheer number: “It takes only one to prove me wrong”, he said. Consensus is not a proof that something is right.

If the science is so clear and the evidence so overwhelming, why not just show that unequivocal evidence to the whole world? Why not debate the other side? If they have no valid arguments, that would be clear rather quickly. Why even bother to make a survey to prove a particular case? Just let the arguments prevail. If you have proof, why even need a consensus?

The more I think of it, the more I am surprised there aren’t more scientists disagreeing with each other. The climate is a very complex research topic and climate science is a relatively young science which only recently got reliable data. Just a few random thoughts about why in my opinion it would be hard to come to a consensus in climate science:

• Many different factors contribute to the outcome.
  Probably not all of them are known. There is still much debate about some of them.
• Those elements are also interconnected.
  Change one and others will also change. CO₂ can raise the temperature. Higher temperatures means more evaporation (which takes energy), but also means more water vapor in the air (which also is a greenhouse gas), but this also means more clouds (which can decrease the incoming radiation of the sun and decrease temperature), but also … etc, etc. Change one element and others will change too to come to a new equilibrium.
• We only have reliable data since let’s say the late 1970s (air temperatures, sea ice, thunderstorms) or even the beginning of the millennium (sea surface temperatures).
  That is not even one complete cycle! Even now we depend on data from which it was never the purpose to monitor climate and have to be interpreted to get a result. It never ceases to amaze me that climate experts prefer the sparse and highly adjusted land surface data set over satellite measurements.
• Most of the doom and gloom scenario’s come from mathematical models.
  Although I am very computer minded and have some programming skills, I fail to understand why one could get accurate results with limited data. In computer science lessons we learned about the gigo-principle (Garbage In → Garbage Out). Climate experts keep telling us that CO₂ is the main driver behind the warming since 1850. I can vividly imagine something when models are trained with a high CO₂ sensitivity and then unsurprisingly show a high temperature increase. Train a model that CO₂ is the main driver and it will get a huge response to more CO₂. That shouldn’t be a surprise to anyone.
• The system is ever changing, with or without us.
  Change is the norm. When I was a believer I was afraid because of the belief that change meant loosing things. While this is perfectly possible, change is not necessarily a bad thing, although it can be. It can cut on both sides. A warming climate can mean we loose something, but it can be beneficial as well. There are many possible effects on both side of the issue. Only focus on the (possible) bad things is a very unsatisfying and depressing way to live. Been there, done that.

In such a complex system, wouldn’t it be more logical that there should be more scientists that disagree with each other? Claiming a consensus in a highly complex system with sparse data seems rather artificially.

Scientifically it doesn’t make much sense, but there definitely are advantages in declaring a consensus. It has important psychological, social and political impacts.

If there is consensus, there is no real need to debate anyone on the science. As Katherine Hayhoe typified this rather clear via Twitter:

I don’t debate unless there’s equal representation (49 pro-climate chg scientists vs 1 against)

Under these conditions the chance of debating anyone with a different view will be minute to non existent. That is a real comfortable position one can be in. But even if this is an extreme example, in the real world there is not much of a debate going on. There are eminent scientists on both side of the debate. It would be refreshing to hear the arguments from the two sides and to take them on their own merits, not whether they come from the “consensus” or the “non-consensus” side of the issue.

Another advantage by declaring a consensus: there is safety in numbers. As a layman, consensus is reassuring. It relieves us from digging in the matter and try to understand it to form our own opinion. It also would make us more susceptible to (severe) measures decided by the politicians. Here we come back to the conclusion of the Cook survey:

The public perception of a scientific consensus on AGW is a necessary element in public support for climate policy.

Translate this to the real world: unless the public has the perception that there is a consensus among scientists that anthropogenic causes are the main driver of global warming, governments will not likely do something. Was it the purpose of the paper to declare a consensus to facilitate climate policies?