Edward Norton Lorenz (1917–2008), the American mathematician and meteorologist, apparently thought that earth’s climate system displayed both ergodic and non-ergodic elements:
“… let us recall that a dynamic system is termed ergodic if the equations describing its evolution at random initial conditions and fixed external parameters have a unique possible stationary solution. If the dynamic system is not ergodic, then its behaviour over an infinitely large time interval will depend on the initial conditions. As applied to the climatic system this is equivalent to the fact that external parameters uniquely determine climate in the first case and non-uniquely in the second case.The climate system is highly complex and the further into the future one goes, the greater the uncertainty associated with what the weather will be like on any particular day. In fact, one might argue that, as soon as one goes from the very short term future (say, hours, days and weeks at most), it must become extremely difficult if not impossible to predict the weather. Certainly, predictions cannot yield objective probability scores, and there are high degrees of increasing uncertainty involved as one moves to the future.
The idea of the non-uniqueness of Earth’s climate was first put forward by Lorenz (1979), who termed ergodic systems transitive, and those systems which do not have the property of transitivity intransitive. The real climatic system, according to Lorenz, is almost intransitive, that is, it shows signs of transitivity and intransitivity simultaneously. Alternation of glacial and interglacial epochs over the last 3.5 million years of Earth’s history testified to this. (Kagan 1995: 15).
Nevertheless, there are certain predicable cycles: the changes caused by days and nights, the changes of seasons, and (generally speaking) Ice Ages.
So the system seems simultaneously ergodic and non-ergodic, and one must wonder whether in economic life we also face a number of such complex processes that have the property of being both ergodic and non-ergodic. For example, business cycles are a real and repeated empirical regularity in modern capitalist systems. Asset bubbles and their collapse appear in an admittedly highly irregular but cyclical way on unregulated or poorly regulated secondary asset markets, even though strict prediction of quantities and turning points with mathematic probability is not possible and movements of specific prices on secondary asset markets are surely non-ergodic.
Kagan, B. A. 1995. Ocean-Atmosphere Interaction and Climate Modelling (trans. Mikhail Hazin), Cambridge University Press, Cambridge.
Lorenz, Edward N. 1979. “Forced and Free Variations of Weather and Climate,” Journal of Atmospheric and Oceanic Science, 36.8: 1367–1376.