The letter (of May 28) from the doctors about climate change and health is a classic example of the logical fallacy that permeates so many public statements about climate policy. There are two elements in their argument: first, that climate change is a scientific fact and, second, something must be done. It is not necessary to dispute the first part, though the letter overstates the degree of consensus upon the extent and consequences of climate change with respect to health. The difficulty is that the averages that are usually quoted provide little guide to the range of reasonable outcomes in particular countries or regions. It is simply not possible to model the direct impact of climate change on health, let alone indirect impacts through nutrition, living standards, etc.

Most claims made by “scientists” about such matters rest on naive models that take no account of normal adjustments to a changing market and natural environment — very similar to the assertions in the 1970s that the world was going to run out of all kinds of natural resources. But even if everything that your correspondents claimed were true, it does not follow what, if anything, should be done. This is an economic and political choice on which reasonable opinions can and do differ. Some amount of climate change is unavoidable, so funding adaption is essential. Spending large sums for the purpose of mitigating future climate change has important implications for current and future wellbeing. There are fundamental disputes about the trade-offs that should be made between the different uses of resources today and in the future — and, thus, the correct balance between adaption and mitigation.

Many economic models indicate that the present value of damage caused by climate change is far less than the costs of mitigation that is being proposed. Other economists take a different view, but the notion that there is a consensus on what action is necessary is not true.