Guest post by Antonis Christofides – A Random Walk On Water”
Despite the heated controversy about AGW, most skeptics share much with the warmists. They share the idea that climate changes are necessarily the result of identifiable exogenous causes, the most popular suggested causes for the current climate change being anthropogenic CO2 emissions and variation in the Sun’s output. They also share the principle that it may, in theory, be possible to determine the net effect of such forcings, although in practice it may be difficult because of the multitude of feedbacks and other uncertainties; and the disagreement is usually on whether science and technology have advanced enough to substantially reduce these uncertainties.
But what if the principle is wrong? Is it possible that, even if we knew climate dynamics in detail and accurately, or if we had abundant computing power, we would be as uncertain about the future evolution of the climate as we are today? What if climate is not something certain that is hidden behind uncertainties, but it is something uncertain in its essence? And what is the difference between the two?
Last year Demetris Koutsoyiannis was awarded the Henry Darcy Medal by the European Geosciences Union, and his new paper, “A random walk on water” (http://www.itia.ntua.gr/en/docinfo/923/ – [in the journal Hydrology and Earth System Sciences]), which he prepared on that occasion, is a highlight of his research. In the paper, he answers the above questions in a straightforward manner. He creates a caricature model of a hydrological system, with very simple and fully known deterministic dynamics, with constant external forcings and with only two internal state variables. The model is so simple that you can recreate it yourself on a spreadsheet and repeat his calculations as you read. Near the end of page 4, just when you will be tempted to think that the analysis of the toy model has come to an end, Koutsoyiannis starts to explore its behaviour deeper and deeper, introducing you to chaos, to the emergence of randomness from determinism, to the emergence of determinism from randomness, to what the central limit theorem and the second law of thermodynamics have in common, to the implications of Hurst-Kolmogorov behaviour on the long-term uncertainty of climate, and much more. This is not some speculative opinion paper, but a no-nonsense approach based on solid math. As the pieces of the puzzle fall together in the last pages of the paper, you will be rewarded with exhilarating enlightenment.
Although no-one has challenged Koutsoyiannis’ work, he is often worried that few get the full message. Even people who admire his work sometimes repeat what that very work points out as fundamental errors. This is not because the material is difficult—in fact any graduate with some background in essential calculus and statistics should be able to read the paper. It may be that we have difficulty accepting these ideas when we’ve been unduly accustomed to determinism since our childhood. In any case, Koutsoyiannis often feels a little alone, and he fears that he could be making the human mistake of being blinded by what he believes, and therefore be failing in his pursuit of truth. So if you want to do a favour to him, please read his paper and tell him why he’s wrong. If you find he’s right, you will have done a favour to yourself.