Thursday, August 24, 2006

Natural selection at the universe level; Expectations of Stability

This idea has no doubt been tossed around for hundreds of years, so if anyone knows a good reference on it, let me know please.

The idea is that we should expect our natural environment to have stable equilibrium properties for the simple fact that we exist. If our natural environment were inherently unstable, we would have blown up long ago and would not be here debating the topic. So there is a form of natural selection at work in our physical universe: the fact that our world exists as we know it means that it has to exhibit stable properties.

So what brought this up?

What bothers me, and many others, about the global warming climate models is that the primary forcing of increased CO2 accounts for only a small portion of the predicted warming -- maybe 1 degree centigrade for a doubling of CO2. The rest of the warming comes from positive feedbacks such as changes in clouds, water vapor, and oceans. It turns out that these things are also the least understood in terms of climate theory.

Positive feedbacks tend to cause either the nonexistence of equilibrium or unstable equilibria. In economics, if an increase in demand were to cause price to increase, and the increase in price would in turn INCREASE demand instead of decreasing it (the normal effect) then we would have a positive feedback effect and most likely nonexistence of equilibrium or at least an unstable equilibrium.

The original "Limits to Growth" book put out by the Club of Rome in 1972 argued that we would soon run out of many resources. The modeling in that book had very little in the way of the negative feedbacks that economists believe in: as prices go up, substitution occurs and quantity demanded declines; or as prices go up, quantity supplied increases, thereby also causing the price increase to be limited.

Some of the climate "sceptics" seem to assume that the climate is characterized more by negative feedback effects and stability than the models imply. Lindzen's "iris" theory is one good example of a strong negative feedback effect. I actually do not know if the large climate models are equilibrium models or not. Is the change in CO2 modeled as pushing the climate from one equilibrium to another, or are the models more naive in that they only look at what would be at best characterized as partial-equilibrium effects? To take an economics example, if we assumed that supply is fixed, and then increase demand, we will get a larger predicted price increase than if we allow a new supply-demand equilibrium to develop.

As I think more about the primary chart in Gore's movie, the one showing the thousands of years of fluctuations in CO2 and temperature, what I see is evidence of inherent stability. I don't know what is causing temperature to increase (as it is well known that temperature does increase first) but I don't see the system spiralling out of control. It is cyclical, not exponential. Even if something as potentially important as fluctuations in solar output causes the temperature flux, we still see the Earth's climate move as an equilibrium, negative feedback system.

Now I grant you that the range of equilibrium might imply very large changes in climate, but I think the general philosophic view here is important. Our physical universe might also be very unstable over very long periods of time; we just haven't reached the end of time yet (if the universe is contracting, I guess it is unstable in that we will have another big bang at some point). But look, if our physical universe were so unstable that relatively small changes in exogenous factors (e.g., a 2 percentage point in greenhouse effect forcing) were to cause massive changes in climate, I doubt that we would be here now.

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