Fig. 2

Costs and benefits of mitigation. Decomposition of the change in global consumption relative to the business-as-usual (BAU) scenario under a the full RICE + AIR optimal policy, and b the reference case optimal policy. Health co-benefits and benefits from avoided CO₂ damages are positive, while mitigation costs and aerosol co-harms (climate damage from the co-reduction of cooling aerosols) are negative. The black solid line displays the global net effect. a shows that the net effect on global consumption is immediately positive when health co-benefits are taken into account, in contrast to the reference case (b), which is representative of standard cost-benefit models that do not include health co-benefits and thus imply that optimal climate policy has net costs for much of this century. If health co-benefits are added to the reference policy in b—by adding the light-red bars displayed in a—the global net effect becomes immediately positive, and if health co-benefits were removed from a, the net effect would be negative for most of this century