Decision makers facing emission-reduction targets need to decide which abatement measures to implement, and in which order. This paper investigates how marginal abatement cost (MAC) curves can inform such a decision. We re-analyse a MAC curve built for Brazil by 2030, and show that misinterpreting MAC curves as abatement supply curves can lead to suboptimal strategies. It would lead to (i) under-investment in expensive, long-to-implement and large-potential options, such as clean transportation infrastructure, and (ii) over-investment in cheap but limited-potential options such as energy-efficiency improvement in refineries. To mitigate this issue, the paper proposes a new graphical representation of MAC curves that explicitly renders the time required to implement each measure. Policy relevanceIn addition to the cost and potential of available options, designing optimal short-term policies requires information on long-term targets (e.g., halving emissions by 2050) and on the speed at which measures can deliver emission reductions. Mitigation policies are thus best investigated in a dynamic framework, building on sector-scale pathways to long-term targets. Climate policies should seek both quantity and quality of abatement, by combining two approaches. A "synergy approach" that focuses on the cheapest mitigation options and maximizes co-benefits. And an "urgency approach" that starts from a long-term objective and works backward to identify actions that need to be implemented early. Accordingly, sector-specific policies may be used (i) to remove implementation barriers on negative-and low-cost options and (ii) to ensure short-term targets are met with abatement of sufficient quality, i.e. with sufficient investment in the long-to-implement options required to reach long-term targets.

GHG mitigation potential, Sub-Saharan Africa, Clean development mechanism,

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Rural electrification in France has entered a new growth phase due to: (i) the developmwt of new end-uses of electricity; (ii) the appearance of new requirements pertaining to the environment and supply quality; and (iii) the prospect of new, tighter European standards. This leads to some questions regarding the adequacy of an institutional framework which has survived for several decades without any major modification. We propose a change in the incentive system based on the following steps: (i) spelling out some of these questions, using a description of the changes that have marked rural electr{ficatian in France; (ii) attempting to see them in a new light through an analysis of the development cost of rural grids and the opportunities to realize the cost reductions potentially offered by non-conventional alternatives based on Demand-Side Management; and finally (iii) placing these questions in the general context of an equitable treatment of users and the ensuing balancing-out effort concerning spatial costs in rural areas, considerations zohich have driven the rural electrification system in France from its in ceptian.