Drivers of peak warming in a consumption-maximizing world

Abstract

Peak human-induced warming is primarily determined by cumulative CO₂ emissions up to the time they are reduced to zero^1,2,3. In an idealized economically optimal scenario^4,5, warming continues until the social cost of carbon, which increases with both temperature and consumption because of greater willingness to pay for climate change avoidance in a prosperous world, exceeds the marginal cost of abatement at zero emissions, which is the cost of preventing, or recapturing, the last net tonne of CO₂ emissions. Here I show that, under these conditions, peak warming is primarily determined by two quantities that are directly affected by near-term policy: the cost of ‘backstop’ mitigation measures available as temperatures approach their peak (those whose cost per tonne abated does not increase as emissions fall to zero); and the average carbon intensity of growth (the ratio between average emissions and the average rate of economic growth) between now and the time of peak warming. Backstop costs are particularly important at low peak warming levels. This highlights the importance of maintaining economic growth in a carbon-constrained world and reducing the cost of backstop measures, such as large-scale CO₂ removal, in any ambitious consumption-maximizing strategy to limit peak warming.