Do economists all favour a carbon tax?

By R.A. | WASHINGTON

LAST week, a Twitter conversation broke out among a few economists concerning whether any serious economists opposed a carbon tax. No, concluded the tweeters, but Tyler Cowen begged to differ. Mr Cowen writes that he personally favours a carbon tax but can imagine a number of principled reasons other economists might not.

Why would we expect economists to support a carbon tax? It's very close to the economic ideal. Global warming is a phenomenon associated with emissions of greenhouse gases over and above natural cycles—largely those resulting from the burning of carbon fuels humans have dug up out of the ground. We expect normal economic activity to maximise social good because each individual balances costs and benefits when making economic decisions. Carbon emissions represent a negative externality. When an individual takes an economic action with some fossil-fuel energy content—whether running a petrol-powered lawnmower, turning on a light, or buying bunch of grapes—that person balances their personal benefits against the costs of the action. The cost to them of the climate change resulting from the carbon content of that decisions, however, is effectively zero and is rationally ignored. The decision to ignore carbon content, when aggregated over the whole of humanity, generates huge carbon dioxide emissions and rising global temperatures.