[en] In this paper, the author aims at setting the carbon tax considered as an environment policy instrument in a context of broader challenges like energy security or the upholding of a high level social protection within a context of economy globalization and demographic aging. Using data on the evolution of oil prices, petrol prices, housing prices and available incomes since 1960, he shows that, in fact, the cost of energy has notably decreased over this period. He wanders whether other possibilities than the carbon tax could be used, like for example building renovation programs, whether this carbon tax will impact behaviours, and which economical impact it could have. He discusses how this tax could conciliate environment, job and energy security. He examines competitiveness and social equity issues in relationship with the introduction of this tax. He considers the useful purpose of this tax in front of the current oil prices, and examines the possibility of introducing such a tax in France within the European Union context

[en] The author proposes some analyses and comments about the relationships between experts who have been involved in various conferences and meetings (from Rio de Janeiro in 1992 to Marrakech in 2002) on climate change. He presents the different groups of experts and comments the issues which have been a matter of debate between them for the past fifteen years. For each of these issues, he gives an overview of the expertise status, highlights consensus as well as dissensus. He compares this expertise with the content of political discourses, and then shows which mechanisms led to The Hague failure and to the incomplete Marrakech's compromise

[en] On October 12, 2007, the Nobel peace price was awarded to Al Gore and to the less mediatized IPCC (intergovernmental panel on climate change). This awarding to a group of scientists may look surprising. However, it just reflects the fear that climatic change represents a threat for the international safety. It shows that any mastering action of this global warming involves a very strategical sector, the energy sector, and disturbs our ways of producing, of consuming and of transporting ourselves. It is of prime importance to maintain the dialogue between the supporters of the two opposite visions of the world with contradictory interests, since the climate topic is a strong source of potential conflicts. This is one of the missions of the IPCC, a group of experts elected by their peers to establish a state-of-the-art of the scientific knowledge about climate change. This original scientific institution intercedes here not as a judge but as a warrant of the truthfulness of the informations in domains where the knowledge remains fragile and disputed. This dossier presents the contribution of the IPCC (GIEC in French) to the climate change debate, and the CIRED, a mixed research unit involved in the sustainable development issue. (J.S.)

[en] What shall we do in front of climatic change? Considering the potential seriousness of global risks, shall we start drastic policies of abatement of greenhouse gas emissions? Taking into account the cost of these policies and the uncertainties about the reality of risks, should we postpone the action? Do the efforts of emissions abatement make a good use of rare resources when the stake is only to gain few degrees of temperature and while we need today urgent developments to fight against poverty? One of the priorities of CIRED, a mixed research unit involved in the sustainable development issue, is to clarify the terms of the debate in order to avoid its transformation into a conflict which would paralyze any significant action. To do so, CIRED has elaborated 'integrated' models which allow to study the optimal answer to be adopted considering the size of uncertainties and the forcefulness of the controversies which characterize this subject. (J.S.)

[en] This paper addresses the timing of the use of biological carbon sequestration and its capacity to alleviate the carbon constraint on the energy sector. We constructed a stochastic optimal control model balancing the costs of fossil emission abatement, the opportunity costs of lands allocated to afforestation, and the costs of uncertain climate damages. We show that a minor part of the sequestration potential should start immediately as a 'brake', slowing down both the rate of growth of concentrations and the rate of abatement in the energy sector. thus increasing the option value of the emission trajectories. But, most of the potential is put in reserve to be used as a 'safety valve' after the resolution of uncertainty, if a higher and faster decarbonization is required: sequestration cuts off the peaks of costs of fossil abatement and postpones the pivoting of the energy system by up to two decades. (authors)

[en] This paper aims at clearing up misunderstandings about the distributive impacts of carbon taxes, which proved to be a decisive obstacle to their further consideration in public debates. It highlights the gap between partial equilibrium analyses, which are close to the agents' perception of the costs of taxation and general equilibrium analyses, which better capture its ultimate consequences. It shows that the real impact on households' income inequality is not mechanically determined by the initial energy budgets and their flexibility but also depends upon the recycling modes of the tax revenues and their general equilibrium effects. The comparison of five tax-recycling schemes highlights the existence of trade-off between maximizing total consumption, maximizing the consumption of the low-income classes and reducing income inequality. (authors)

[en] The inauguration of the prospective modeling chair in favour of sustainable development is the result of the joint effort of several schools, organizations and companies, in particular: Mines ParisTech, Ponts ParisTech, Agro ParisTech, the higher education and research pole of ParisTech, the Ecole des Ponts foundation, the mineral, mining and metallurgic industries foundation (FI3M), with the partnership of Ademe, EdF, Renault, Schneider Electric and Total. The main goal of this chair is to perpetuate modeling tools with sustainable development stakes. The scientific program and the expertise of this chair are based on the joint and complementary experience of its two co-founder research teams in the domain of long-term prospective of energy, economy and environment-related questions: the applied mathematics centre (CMA - Mines ParisTech) and the international centre of environment and sustainable development research (CIRED). An inaugural colloquium was organized at the occasion of the launching of this chair. During round tables, representatives of the different intervening parties explained the stakes of this huge project and their expectations, in particular from the scientific, economical and societal point of view. A workshop on the topic 'carbon and prospective' followed the round tables. Six presentations were given about the following topics: energy policy scenarios for 2050 (Moncomble, J.E.), the shadow price of carbon (Chambolle T.), mitigation targets and carbon values: insights from TIMES-FR (Assoumou E.), climate protection and infrastructures (Sassi O.), China's energy and carbon options (Wenying C.), EU 20-20 policy implications on the energy system of Germany - an analysis with TIMES PanEU (Blesl M.). This book gathers the proceedings of both parts of this colloquium, the debates during the round tables (in French) and the presentations given during the workshop (in English). (J.S.)

[en] This paper envisages endogenous technical change as resulting from the interplay between the economic growth engine, consumption, technology and localization patterns. We perform numerical simulations with the recursive dynamic general equilibrium model IMACLIM-R to study how modeling induced technical change affects costs of CO₂ stabilization. IMACLIM-R incorporates innovative specifications about final consumption of transportation and energy to represent critical stylized facts such as rebound effects and demand induction by infrastructure and equipments. Doing so brings to light how induced technical change may not only lower stabilization costs thanks to pure technological progress, but also triggers induction of final demand - effects critical to both the level of the carbon tax and the costs of policy given a specific stabilization target. Finally, we study the sensitivity of total stabilization costs to various parameters including both technical assumptions as accelerated turnover of equipments and non-energy choices as alternative infrastructure policies. (authors)

[en] The actual main objective of international negotiations on climate change aims at elaborating a coordination regime integrating developing countries. The international coordination system built at the Kyoto Conference relies on a coordination system based on quantity based objectives. This architecture is more the result of successive compromises rather than the result from the deployment of an ex-ante fully-fledged vision of any actor, and its elaboration has been fully disconnected from development issues. In addition to the impossibility to get an agreement on rules for quota allocation among all the parties, this system shows irreconcilable contradictions between climate and development issues. This article aims, starting fi-om examples of synergies between climate and development, at enunciating bases of an amended Kyoto Protocol which could bridge the gap between climate and development. (authors)

[en] This research aims at clearing up misunderstandings about the distributive impacts of carbon taxes, which proved to be a decisive obstacle to their further consideration in public debates. It highlights the gap between partial equilibrium analyses, which are close to the agents' perception of the costs of taxation, and general equilibrium analyses, which better capture its ultimate consequences. It shows that the real impact on households' income inequality is not mechanically determined by the initial energy budgets and their flexibilities but also depends upon the way tax revenues are recycled and its general equilibrium consequences. The comparison of five tax-recycling schemes highlights the existence of trade-off between maximizing total consumption, maximizing the consumption of the low-income classes and reducing income inequality. (authors)