06122010

Climate models are just wrong..

See this article on WUWT for more details. The paper in summary says

"..we think that the most important question is not whether GCMs can produce credible estimates of future climate, but whether climate is at all predictable in deterministic terms."

The basic assumption that something as complex, irregular and none deterministic as the world climate can be usefully modeled over an extended period of time based on sparse measurement and fixed equations we have always felt to be just wrong.

Look, its one thing to model say as a single material within a well defined environment by decomposing it into a series of blocks and modeling through equations the interactions betweens those cells to determine some state in the future. This is something engineers and scientists do on a regular basis with useful results.

It is something completely different to model an in essence infinity complex climatic system that over times evolves in of itself in how it behaves and exactly what is considered to be 'climate' at any one point in time - i.e. chemicals, compounds and energy in various forms regularly and naturally come and go in and out of the system all the time. There is no such thing as a 'machine to dismantle' and the paper hints at this:

"Several publications, a typical example being Rial et al. (2004), point out the difficulties that the climate system complexity introduces when we attempt to make predictions. “Complexity” in this context usually refers to the fact that there are many parts comprising the system and many interactions among these parts. This observation is correct, but we take it a step further. We think that it is not merely a matter of high dimensionality, and that it can be misleading to assume that the uncertainty can be reduced if we analyse its “sources” as nonlinearities, feedbacks, thresholds, etc., and attempt to establish causality relationships."


Also there is the not insignificant fact that we can only measure the climate globally via a very very thinly spread set of sensors using what we consider to be the important markers within the climate. There are two problems here, first the inherent error introduced by sparse measurements, and the second is the assumption what is being measured is actually significant to the operation of the climate as a whole and not just significant to human life (i.e. we could well be measuring the wrong things!).

Also if you add on this the basic problem that any algorithmic implementation on a computer run to enough iterations will accumulate enough numerical approximation errors that the results will be meaningless (i.e. a 1/3 cannot be exactly represented on a computer, it ends up as something like 0.3334, combine this with a limit on the number of significant digits that can be represented in a floating point number and you can quickly see that without very careful forethought errors can quickly and quietly accumulate).

All these factors combined are why even basic medium to long term weather forecasting is known to be an inexact science - its basically a 'best guess' at what could happen. Beyond this point in time the results become not worth considering, they are more wrong than right.

The same logic applies to whole world climate models, plus they very quickly are overcome by the fact that the real climate system 'evolves' away from what the models were designed to reproduce. This cannot be fixed using current techniques as how do you know which way it will evolve?

Therefore I urge you indeed to take with a very large (perhaps planet sized) pinch of salt any of the results presented up as 'fact' from either singular or multiple climate models - they are all fatally flawed and equally as useless. So by implication this also means the IPCC assessments of the climate are fatally flawed, something very important to remember when you see what is currently going on in your name at Cancun...

BTW We do care a lot about the environment, what we object to is the poor science that is being used as the basis to implement essentially untested and ill proven solutions to a weakly defined problem. As said before we think environmental degradation is the real enemy at the gate.