The magnitude of global surface temperature change in response to unit radiative forcing depends on the type and magnitude of forcing agent -- a concept known as a "forcing efficacy". In this study, we perform a set of simulations using a climate model to calculate the efficacy of 10 different forcing agents defined in terms of fixed-SST effective radiative forcing, and then use a Green's function approach to show that each forcing efficacy can be largely understood in terms of the radiative feedbacks associated with the different surface temperature patterns induced by the forcing agents (a pattern effect). We also quantify how the state dependence of feedbacks on global mean surface temperature anomalies impacts forcing efficacies, and the results show that the forcing efficacy can be well reconstructed with a combination of pattern effect and state dependence. Our results indicate that the efficacy of aerosol forcings depends on the spatial location of aerosol concentration changes, and the effect of forcing efficacy on Earth's energy budget can be accounted for by considering the pattern effect and state dependence of radiative feedbacks.