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Mathematical modelling illusions : Comments
By Jay Lehr and Tom Harris, published 11/1/2019Although one of the most active areas for mathematical modeling is the economy and the stock market, no one has ever succeeded in getting it right.
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Create a series of equations and algorithms that you think is a reasonable representation of the global climate system, and then see what happens when you increase the level of CO2 in your model. If it shows catastrophe, publish and await the accolades. If it doesn't...well no one cares. You definitely won't be published.
The same process is used for the economy for a very long time, but remains profoundly inaccurate despite a century's refinement.
The problems for both is that these are unbelievable complex systems that cannot be reduced to a few equations or even a few thousand equations.
Additionally, the climate is only vaguely understood and therefore the equations used to represent some aspect of the climate might be spectacularly wrong. (Vaguely understood?. Only this week it was realised that the deep Pacific Ocean is very much colder than thought and getting colder, caused, it seems, by the slow reaction to the Little Ice age 400 years ago).
I think the most important take is that, as climate models have become more sophisticated and better represent the real climate system, the forecast temperature rises have become less scary. There was a time when models didn't and couldn't represent clouds in their calculations. Criticism forced a major effort to better model clouds and the result was that predictions of the future temperature increases fell.
There is a very important number in climate science called ECS: Equilibrium Climate Sensitivity. That is the amount of expected change in temperatures for a doubling of CO2, all else being held constant. Its the starting point for all predictions and all modellers have to tell their systems what ECS to use. As the science has improved, the value of the ECS has declined. Each new discovery has caused a decline in this core number. Each new discovery WILL caused a decline in this core number.
As the science improves, the scare recedes. Not that you'd know that from the headlines