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Having experienced low prices for about a decade, the European Union Emissions Trading System has been supplemented with the market stability reserve (MSR) that adjusts the supply of allowances to market outcomes. We critically review the literature assessing the performance of the MSR against several policy objectives. In doing so, we cover both conceptual aspects and quantitative assessments. We conclude by pointing out important policy implications and open issues for further research.

Deep decarbonization of energy systems poses considerable challenges to electricity markets and there is a growing consensus that an energy-only design based on short-term marginal cost pricing cannot deliver adequate levels of investment and long-term coordination across actors and sectors. Based on the instructive example of the evolution of European electricity market designs, we discuss several shortcomings of energy-only markets and illustrate how ad-hoc policies that intend to address them have limitations of their own, notably a lack of systemwide coordination. Second, we describe how the sheer scale and nature of deep decarbonization targets requiring massive investment in capital-intensive low-carbon technologies exacerbate these issues. Ambitious emission reduction targets thus require an evolution of market design towards hybrid regimes. Hybrid markets separate long-term investment decisions from short-term operations through a balanced and differentiated use of competitive and regulatory design elements to coordinate and de-risk investment. Finally, a historical analysis of the evolution of different electricity market designs shows how hybrid markets constitute contemporary forms of long-run marginal cost pricing that are appropriate for meeting deep decarbonization targets with reduced uncertainty and hence lower private and social costs.

We develop an equilibrium model of emissions permit trading in the presence of fixed and proportional trading costs in which the permit price and firms' participation in and extent of trading are endogenously determined. We analyze the sensitivity of the equilibrium to changes in the trading costs and firms' allocations, and characterize situations where the trading costs depress or raise permit prices relative to frictionless market conditions. We calibrate our model to annual transaction data in Phase II of the EU ETS (2008–2012) and find that trading costs in the order of 10 k€ per annum plus 1 € per permit traded substantially reduce discrepancies between observations and theoretical predictions for firms’ behavior (e.g. autarkic compliance for small and/or long firms). Our simulations suggest that ignoring trading costs leads to an underestimation of the price impacts of supply-curbing policies, this difference varying with the incidence on firms.

We develop an emission permits trading model where covered firms can (1) utilize rolling planning horizons to deal with uncertainty and (2) exhibit bounded responsiveness to supply-side control policies. We calibrate the model to reproduce annual market outcomes in the EU ETS over 2008–2018 and show that a rolling finite horizon reconciles the banking dynamics with discount rates implied by futures contracts’ yield curves. It also replicates the price dynamics well compared to a standard infinite horizon, including the new price regime induced by the 2018 market reform. We then use our calibrated model to decompose the impacts of the 2018 reform's design elements, quantify how they hinge on the firms’ horizon and responsiveness, and highlight important implications for policy design. For instance, when firms utilize rolling horizons, the Market Stability Reserve can improve effectiveness by frontloading abatement efforts and induce lower cumulative emissions compared to an infinite horizon.

We formally study the determinants, magnitude and distribution of efficiency gains generated in multilateral linkages between permit markets. We provide two novel decomposition results for these gains, characterize individual preferences over linking groups and show that our results are largely unaltered with strategic domestic emissions cap selection or when banking and borrowing are allowed. Using the Paris Agreement pledges and power sector emissions data of five countries which all use or considered using both emissions trading and linking, we quantify the efficiency gains. We find that the computed gains can be sizable and are split roughly equally between effort and risk sharing.

Linkages between Emissions Trading Systems are deemed an important element of the future climate policy landscape. They are, however, difficult to agree and remain few and far between. Temporary restrictions on permit trading have potential to facilitate and gradually approach unrestricted, full linkage. We compare the relative merits of several link restrictions in this respect, namely quantitative transfer limits, border taxes on transfers, exchange and discount rates, and unilateral linkage. To this end, we develop a simple model to have a unifying framework which, in conjunction with lessons we draw from realworld experiences, serves as a basis for a broader, policy-oriented discussion. While quantitative restrictions seem to be the natural route to full linkage, they can lead to uncertain distributional effects and weaken price signals. These aspects are mitigated under a border permit tax, but this policy seems harder to implement. Exchange rates have potential to adjust for programmes’ stringencies and raise ambition over time, but can be challenging to select. As experience corroborates, unilateral linkage can be a convenient approach.