This paper reviews different methods for assessing and comparing across countries the impact of climate change mitigation policies and policy packages on emissions. Broadening and deepening past and recent mitigation policies’ stocktaking efforts, as well as mapping them to their emission base, is key to comparing pricing and non-pricing policies and feed comparable information to ex-post empirical and ex-ante analytical models. Ex-post empirical approaches can provide benchmark estimates of policies' effectiveness from past data and furnish key parameter estimates to calibrate ex-ante analytical models (partial equilibrium, general equilibrium and integrated assessment models).

Moreover, they can complement ex-ante analytical models by empirically validating their assumptions and informing models’ choices. Ex-ante analytical modelling are well suited to provide long-term forward-looking projections also on yet-to-be implemented policies. Sector specific models, such as energy system models, are well suited for a granular assessment of the impact on emissions of a wide range of price- and non-price-based policies. Outputs from the ex-ante sector-specific models can then feed into a Computable General Equilibrium model to quantify the effect of individual policies and policy packages on emissions, taking into account second order effects and reducing the risk of double counting the effect of policies.