On one side, there has been dramatic progress in renewable energy technology, with the costs of solar power, in particular, plunging, down by half just since 2010. Renewables have their limitations — basically, the sun doesn’t always shine, and the wind doesn’t always blow — but if you think that an economy getting a lot of its power from wind farms and solar panels is a hippie fantasy, you’re the one out of touch with reality.
On the other side, it turns out that putting a price on carbon would have large “co-benefits” — positive effects over and above the reduction in climate risks — and that these benefits would come fairly quickly. The most important of these co-benefits, according to the I.M.F. paper, would involve public health: burning coal causes many respiratory ailments, which drive up medical costs and reduce productivity.