Modak, Angshuman; et al. (2016): Why must a solar forcing be larger than a CO 2 forcing to cause the same global mean surface temperature change?

Modak, Angshuman; Bala, Govindasamy; Cao, Long; Caldeira, Ken (2016): Why must a solar forcing be larger than a CO 2 forcing to cause the same global mean surface temperature change? In Environ. Res. Lett. 11 (4), p. 44013–44013. DOI 10.1088/1748-9326/11/4/044013.

„In this study, we investigate the physical mechanisms responsible for the lower efficacy of solar forcing compared to an equivalent CO₂ forcing. Radiative forcing is estimated using the Gregory method that regresses top-of-atmosphere (TOA) radiative flux against the change in global mean surface temperature. For a 2.25% increase in solar irradiance that produces the same long term global mean warming as a doubling of CO₂ concentration, we estimate that the efficacy of solar forcing is ~80% relative to CO₂ forcing in the NCAR CAM5 climate model.“

Link