Deep-seated, persistent uncertainty is a pernicious feature of climate change. One key parameter, equilibrium climate sensitivity, has eluded almost all attempts at pinning it down more precisely than a ‘likely’ range that has stalled at 1.5–4.5°C for over thirty-five years. The marginal...

This paper introduces geoengineering into an optimal control model of climate change economics. Together with mitigation and adaptation, carbon and solar geoengineering span the universe of possible climate policies. We show in the context of our model that: (i) a carbon tax is the optimal...