Prudent carbon dioxide removal strategies hedge against high climate sensitivity

Uncertainty in climate sensitivity has been shown to warrant early-on mitigation to limit global warming while anticipating future carbon dioxide removal creates mitigation deterrence. Here we use an integrated assessment model to quantify the impacts of under- or overestimating the cost and availability (feasibility) of carbon dioxide removal when limiting warming to 1.5 °C by 2100 under uncertain climate sensitivity. If climate sensitivity uncertainty is disregarded, initial assumptions on the feasibility have only minor effects on mitigation costs. However, the climate sensitivity risk compounds the impact of prior assumptions. Wrong assumptions on carbon dioxide removal feasibility can lead to lower costs under extreme realizations of climate sensitivity. Moreover, scenarios considering uncertainty in climate sensitivity rely less on carbon dioxide removal. A prudential strategy assuming low feasibility for carbon dioxide removal reduces the “double whammy” risk of overestimating carbon dioxide removal in combination with a realization of high climate sensitivity.