A Case of Posthumous Conscription
To get from there to the conclusion that he would have favored a carbon tax requires at least one further step, a reason to think that he would have believed that global warming due to CO2 emissions produced net negative externalities large enough to justify doing something about them. The problem with that claim is that warming can be expected to produce both negative externalities such as sea level rise and hotter summers and positive ones such as longer growing seasons and milder winters. The effects will be spread out over a long and uncertain future, making their size difficult to estimate. My own conclusion, defended in past posts here (one example), is that the uncertainties are large enough so that one cannot sign the sum, cannot say whether the net effect will be positive or negative.
The article quotes professor Greenstone on the uncertainty:
Estimating the cost is tricky, Greenstone said, but scientists and economists have models for projecting the cost of each added ton of carbon on agricultural losses, mortality, sea-level rise, storm surge, and other climate effects.
It’s a complicated task but I think the best evidence suggests that it’s probably around $40 a ton,” he said. The U.S. government has projected the cost of carbon emissions at $37 per ton.
One would expect similar effects from any substantial reduction in the cost of other alternatives to fossil fuels, such as nuclear or solar power, or from a substantial increase in the cost of fossil fuels due to the exhaustion of the more readily accessible sources. Additional uncertainties are associated with the relevant climate science. The IPCC, for example, claimed in its fourth report that warming increased drought, retracted that claim in the fifth report.
Whether or not my view that we cannot sign the externality is correct, I would be very surprised if Professor Greenstone could justify his confidence in the specific number he offered—which happens to be close to the official government estimate. I would be equally surprised if he could offer evidence that Milton Friedman would have taken seriously a government estimate of an uncertain number offered in support of a policy the current administration favored.
Before they died, my parents created a foundation to promote the idea of school choice. One of the terms on which they created it was that the foundation was to end a fixed number of years after the last of the founders died. The reason for that was my father's concern, possibly based on the examples of the Ford and Rockefeller Foundations, that once the founders were no longer around their names would be used in support of policies they themselves would not have supported.
P.S. Robert Murphy points at evidence against the claim that my father would have supported a carbon tax. In a 1999 comment to a recently published book, he wrote:
This encyclopedic and even-handed survey of the evidence of global warming is a welcome corrective to the raging hysteria about the alleged dangers of global warming. Moore demonstrates conclusively that global warming is more likely to benefit than to harm the general public.It is possible that between then and now he would have reversed his view, but I can see no reason to expect it.