Kurt Cobb: Characterizing the incalculable

It would be nice to be certain about the future. But, absent time travel, no one can be certain about anything that hasn’t happened yet. So, as a substitute many specialists build models in disciplines as disparate as finance and physics to guess what the future might look like given certain assumptions.

In physics the models we have for describing the universe and its properties can be remarkably predictive if they only require input based on the laws of physics. But we have considerably more trouble describing the social world of humans and the interactions of human society with nature. This is because we don’t have laws of human behavior that can be nailed down in the same precise, repeatable way that laws of physics can.

The upshot is that we can calculate the probability of a comet hitting a planet with some precision. But we cannot calculate the probability of the stock market going up or down in the next five years. Nor can we calculate the probability of any particular outcome of climate change because what we humans do in the future is such an important factor in determining that outcome. The modeling of climate is also problematic because the climate system itself–even absent any human interference–is so complex that we do not fully understand it.

A rule of thumb then might be that the more complex the system, the less likely it is we will be able to model its actions with precision. And, the greater the number of humans involved in affecting that system and the deeper that involvement, the more difficult it becomes to design precise models of the system. In general, the reliability of a model decreases as the complexity of the system it is modeling increases.

Energy Bulletin