Solar geoengineering is no substitute for cutting emissions, but could nevertheless help reduce the atmospheric carbon burden. In the extreme, if solar geoengineering were used to hold radiative forcing constant under RCP8.5, the carbon burden may be reduced by ~100 GTC, equivalent to 12–26% of twenty-first-century emissions at a cost of under US$0.5 per tCO2.
Keith, David W., Gernot Wagner, and Claire L. Zabel. "Solar Geoengineering Reduces Atmospheric Carbon Burden." Nature Climate Change 7 (September 2017): 617-619.