Since Judith Curry has a guest post about global climate models and the laws of physics, I thought it would be worth posting this recently released video of a talk about climate modelling (see below). It’s by Steve Easterbrook, who is a Professor in the Department of Computer Science at the University of Toronto.
One problem with blogosphere critiques of climate models is that it often seems to come from those who might have some relevant expertise, but who have never actually run a climate model, or spent any significant amount of time talking with those who have. They also seem to base their critique on things they’ve read on the internet and – as a result – assume climate modellers do not understand some pretty fundamental things; ignoring that online material about climate models, aimed at the general public, will clearly not include the kind of details that you will find in the scientific literature. Additionally, they assume that climate modelling should be conducted in a manner similar to what they themselves might have experienced, ignoring that what might work in one field, might not in another.
What Steve Easterbrook did was spend a lot of time at the UK’s Met Office, interacting with – and learning from – those who do run, and develop, climate models. He found that there are reasons why climate modellers might behave differently to software engineers, or those doing computational modelling in industry. Climate models are scientific instruments. The goal is not to design a new climate, or produce some specific product; the goal is to understand our climate, and how it might respond to changes. He also discussed how they continually test the models and how there are very few defects, per thousand lines of code. His argument for this being that in such a code, it can be fairly obvious when there is a problem, and therefore you can find, and fix, defects more easily than might be the case in other codes.
I don’t think I need to say much more. The talk is a little long, but it’s certainly worth watching. Steve Easterbrook’s blog is also very good, and has a number of posts about climate models.
The talk is – I think – from 2011, but has only just been released. As Victor Venema points in the comments on youtube, the paper on which it is based is here.