I think I probably need to take another short break from all of this online nonsense. I’ve recently been commenting on Bishop-Hill and had been quite enjoying it. I’d been accused by other commenters of being patronising and condescending, but that was somewhat intentional. I knew that if I took it seriously, the responses would just wind me up too much. Then, I made the mistake of taking it seriously, and the wheels fell off.
It related to a lengthy discussion about the significance of chaos. It’s clear that our ability to forecast weather events more than a few days in advance is very difficult, if not impossible. This is a consequence of the system being non-linear and, essentially, chaotic. The precise evolution is very sensitive to the initial conditions and since our models can never set the initial conditions with infinite precision, our ability to forecast specific events decreases with increasing time. If you want to know more, you can read the Realclimate post by James Annan and William Connolley, which says,
Although ultimately chaos will kill a weather forecast, this does not necessarily prevent long-term prediction of the climate. By climate, we mean the statistics of weather, averaged over suitable time and perhaps space scales (more on this below). We cannot hope to accurately predict the temperature in Swindon at 9am on the 23rd July 2050, but we can be highly confident that the average temperature in the UK in that year will be substantially higher in July than in January. …… models based on physical principles also reproduce the response to seasonal and spatial changes in radiative forcing fairly well, which is one of the many lines of evidence that supports their use in their prediction of the response to anthropogenic forcing.
This is really all I was trying to point out in the discussion. I was also trying to stress the importance of the boundary conditions. Our climate’s boundary conditions are essentially the albedo, the solar insolation, and the composition of our atmosphere (the greenhouse effect). These boundary conditions broadly set the overall of state of our climate, which is essentially a consequence of energy conservation (these boundary conditions will set the equilibrium temperature at which we are losing as much energy as we gain).
It is possible for internal variability to influence some of these boundary conditions, but we have little evidence to suggest that it can have a significant impact in our current climate state. There’s a suggestion that it can have a small impact that may last a decade or so (see this post) and there is some evidence to suggest that some of our past climate changes were internally forced. However, we don’t expect (at the moment) internal variability to play a significant role (it might, but the evidence for this is weak). So, even though the system is inherently chaotic doesn’t mean that it can simply shift into an entirely new state – the overall state of our climate (the conditions averaged over a suitable time interval) are largely constrained by the boundary conditions.
Well, this discussion didn’t go well. Apparently the boundary conditions are irrelevant in a chaotic system, and why was I so focused on energy conservation anyway (because it’s a fundamental law of physics, maybe). My tolerance – which had already been strained – disappeared when someone (who shall remain nameless) popped along to point out that I was an idiot because it is indeed possible for non-linear dynamical systems without boundary conditions to simply shift into an entirely different state. Well, yes, because it’s a non-linear, dynamical system WITHOUT BOUNDARY CONDITIONS! Telling me I’m an idiot because a system that is not really comparable to our climate can do something our climate probably can’t do, is a remarkably poor rebuttal.
Anyway, I need to finish working through some lecture notes, finish working on a paper (which happens to be on a non-linear, dynamical system – I hope I know what I’m doing) and take a few deep breaths. I think I’m now being moderated on Bishop-Hill as my comments weren’t appearing. I haven’t gone back to check recently, so they may have appeared now. I’m kind of hoping Andrew Montford will ban me. Not so that I can then complain about it, but so that I can stop wasting my time there. I’m well aware that I don’t have much self-control, so Andrew would be doing me a favour if he were to do so.