I have reached the end of the discussion on Message from Scott Sumner in which he discusses global warming. I posted a comment but it was probably too late for most people to notice.
I think the problem is more complicated than Scott seems to suggest.
Scott writes:
The theory suggests that higher levels of CO2 should increase global temperatures due to the “greenhouse effect”.
TRUE.
But what this doesn’t tell us is the strength of the effect. I don’t disagree with Scott. I’m just saying that the effect could be strong or weak. If a substantial increase in CO2 led to a temperature increase of 0.1 degrees Celsius, we would have nothing to worry about. We can’t just look at the fact that CO2 increased, then temperature, and attribute all the temperature increase to CO2 increasing.
Let’s take an example from the world of economics, which Scott and I are of course more familiar with. We posit that a substantial increase in the minimum wage will result in a substantial reduction in the number of jobs for low-skilled workers. It’s simply good economic theory. So we look at the data and find that, indeed, an increase of a few dollars an hour in the minimum wage is accompanied by a substantial reduction in the number of jobs for low-skilled workers.
But that doesn’t tell us how much of the job reduction is due to the minimum wage increase.
Likewise, it is poor methodology to focus on one variable, CO2 concentration, and not examine other factors that could cause global warming.
