When GHG concentrations vary, the radiative imbalance that is created can persist for a period of time as the system
adjusts. Thus there may be lagged effects from the forcing factors. However, due to the approximate exponential shape of
f(eCO2), lagged effects from this term are already effectively incorporated in the model. This follows because the sum of
lagged terms of an exponentially shaped covariate is proportional to the same non-lagged covariate. Also, cross autocorrelation
plots between each forcing term and the innovation residuals strongly indicate that lagged effects are accounted for by
the model (Fig. 5d).