More on climate change

Scott Adams has an interesting breakdown here of his view on climate change policy. Fundamentally he notes that to believe we need to disrupt economies and put people out of work to restrain CO₂ production one has to believe a chain of things:

1.      That we have the chemistry and physics right

2.      That we are measuring things (like CO₂ and temperature) right

3.      That the climate models we build are right

4.      That the economic models we build on the basis of the climate model predictions are right.

His assessment of the credibility of each step, which more or less agrees with mine is as follows:

1.      That we have the chemistry and physics right – 100%. We almost certainly have the basic science right.

2.      That we are measuring things (like CO₂ and temperature) right – 85%.  That seems in the right range to me. Measuring global temperature is hard – some places are cooling, some are warming, there is lots of day-to-day and year-to-year and place-to-place variability.  My posting some weeks ago showed how the New York Times claim that 2016 was hotter than the previous year was suspect, since the measured difference was far less than the error of measurement.

3.      That the climate models we build are right – Adams gives that 10% confidence and I would tend to agree.  As I mentioned before, even with our supercomputers and satellite weather systems and closely-spaced ground weather stations we still can’t predict the local weather in our own city more than a few days ahead, or the path of a hurricane more than a few days ahead. So how much confidence can we have in models of the entire global climate years in advance?  The climate models have lots of adjustable parameters embodying various assumptions about how the climate works, and the models that are still around have been carefully “tuned” (by adjusting those knobs) to “predict” the past – which says nothing about how accurate they are about the future. With enough adjustable parameters one can match just about any history, but that doesn't mean the assumptions are correct.

The key issue here is how much effect does CO₂ actually have on climate change – how sensitive is global temperature to CO₂ levels?  How much is the heating from higher CO₂ levels offset by increased cloud formation? How much is it reduced by increased plant growth.? How much of the excess CO₂ is absorbed in the ocean? Etc, etc, etc. We have lots of theories – but only theories. And the theories from respectable climate scientists are all over the place.

4.      That the economic models we build on the basis of the climate model predictions are right – Adams gives that 0% confidence, on the basis that thus far most economic models have been miserably inaccurate, if not completely wrong (like the rosy OMB ObamaCare predictions of how insurance premiums would fall substantially for all of us !!!).

So yes, I am in the end highly skeptical on the evidence available to date that it is imperative that we disrupt the world economy and put hundreds of thousands or millions of people out of work.  Certainly the global climate seems to be warming, and it seems plausible, if not entirely certain, that human activity is at least partly the cause. But the step from there to a belief that CO₂ is the primary cause of climate change, that economic incentives can cause nations to sharply reduce CO₂, and that sharply reducing human CO₂ production will be effective, seems to me tenuous at best.