Figure 4.

Uncertainty in climate sensitivity results in a range of temperature outcomes for a given CO₂-concentration pathway; the multi-model median response and range across the 12 models considered here is shown for the case with long-term CO₂ removal both with and without solar geoengineering. (a) Solar geoengineering could be used to achievea 1.5°C target independent of climate sensitivity uncertainty. (b) The range of forcing from solar geoengineering across the 12 models and from CO_2e; analysis uses % solar reduction and concentration, respectively, but these are plotted as approximate radiative forcing to enable comparison between them. CO₂ forcing is estimated as 5.35 times the log of the concentration change. Because of the short timescales associated with solar geoengineering, uncertainty in climate response can be compensated for with control over solar geoengineering forcing. (Online version in colour.)