Johnson is a climate denier. You can’t refuse to engage with this issue and be anything else. No doubt he is so for all the reasons all those on the right who deny the reality of the climate crisis are. They believe the neoclassical economic assumption that nature is a free gift provided to us (presumably by a paternalistic god) to use without consequence, and that if there is any consequence then the market can in any case instantly correct it.
Externalities, Pigou taxation, that’s all neoclassical stuff. Entirely standard stuff too. What is this drivel he’s on about? As I’ve noted before, this stuff is taught in GCSE economics too.