Person:
Hallegatte, Stéphane
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Fields of Specialization
Green growth,
Climate change,
Urban development
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Last updated
September 13, 2023
Biography
Stéphane Hallegatte is a Senior Climate Change Adviser at the World Bank. He joined the World Bank in 2012 after 10 years of academic research in environmental economics and climate science for Météo-France, the Centre International de Recherche sur l’Environnement et le Développement, and Stanford University. His research interests include the economics of natural disasters and risk management, climate change adaptation, urban policy and economics, climate change mitigation, and green growth.
Mr. Hallegatte was a lead author of the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). He is the author of dozens of articles published in international journals in multiple disciplines and of several books, including Green Economy and the Crisis: 30 Proposals for a More Sustainable France , Risk Management: Lessons from the Storm Xynthia , and Natural Disasters and Climate Change: An Economic Perspective .
He also co-led the World Bank reports Inclusive Green Growth: The Pathway to Sustainable Development , published in 2012 and Decarbonizing Development in 2015, and was member of the core writing team of the 2014 World Development Report Risk and Opportunity: Managing Risks for Development . Most recently, he led the World Bank reports Shock Waves: Managing the Impacts of Climate Change on Poverty , Unbreakable: Building the Resilience of the Poor in the Face of Natural Disasters , and Lifelines: the Resilient Infrastructure Opportunity.
He was the team leader for the World Bank Group Climate Change Action Plan, a large internal coordination exercise to determine and explain how the Group will support countries in their implementation of the Paris Agreement.
Mr. Hallegatte holds engineering degrees from the Ecole Polytechnique (Paris) and the Ecole Nationale de la Météorologie (Toulouse), a master's degree in meteorology and climatology from the Université Paul Sabatier (Toulouse) and a Ph.D in economics from the Ecole des Hautes Etudes en Sciences Sociales (Paris).
Publication Search Results
1 - 10 of 11
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Publication
How Capital-Based Instruments Facilitate the Transition Toward a Low-Carbon Economy : A Tradeoff between Optimality and Acceptability
(World Bank, Washington, DC, 2013-09)This paper compares the temporal profile of efforts to curb greenhouse gas emissions induced by two mitigation strategies: a regulation of all emissions with a carbon price and a regulation of emissions embedded in new capital only, using capital-based instruments such as investment regulation, differentiation of capital costs, or a carbon tax with temporary subsidies on brown capital. A Ramsey model is built with two types of capital: brown capital that produces a negative externality and green capital that does not. Abatement is obtained through structural change (green capital accumulation) and possibly through under-utilization of brown capital. Capital-based instruments and the carbon price lead to the same long-term balanced growth path, but they differ during the transition phase. The carbon price maximizes social welfare but may cause temporary under-utilization of brown capital, hurting the owners of brown capital and the workers who depend on it. Capital-based instruments cause larger intertemporal welfare loss, but they maintain the full utilization of brown capital, smooth efforts over time, and cause lower immediate utility loss. Green industrial policies including such capital-based instruments may thus be used to increase the political acceptability of a carbon price. More generally, the carbon price informs on the policy effect on intertemporal welfare but is not a good indicator to estimate the impact of the policy on instantaneous output, consumption, and utility. -
Publication
Long-Term Mitigation Strategies and Marginal Abatement Cost Curves : A Case Study on Brazil
(World Bank, Washington, DC, 2014-03)Decision makers facing abatement targets need to decide which abatement measures to implement, and in which order. This paper investigates the ability of marginal abatement cost (MAC) curves to inform this decision, reanalysing a MAC curve developed by the World Bank on Brazil. Misinterpreting MAC curves and focusing on short-term targets (e.g., for 2020) would lead to under-invest in expensive, long-to-implement and large-potential options, such as clean transportation infrastructure. Meeting short-term targets with marginal energy-efficiency improvements would lead to carbon-intensive lock-ins that make longer-term targets (e.g., for 2030 and beyond) impossible or too expensive to reach. Improvements to existing MAC curves are proposed, based on (1) enhanced data collection and reporting; (2) a simple optimization tool that accounts for constraints on implementation speeds; and (3) new graphical representations of MAC curves. Designing climate mitigation policies can be done through a pragmatic combination of two approaches. The synergy approach is based on MAC curves to identify the cheapest mitigation options and maximize co-benefits. The urgency approach considers the long-term objective (e.g., halving emissions by 2050) and works backward to identify actions that need to be implemented early, such as public support to clean infrastructure and zero-carbon technologies. -
Publication
Transition to Clean Capital, Irreversible Investment and Stranded Assets
(World Bank, Washington, DC, 2014-05)This paper uses a Ramsey model with two types of capital to analyze the optimal transition to clean capital when polluting investment is irreversible. The cost of climate mitigation decomposes as a technical cost of using clean instead of polluting capital and a transition cost from the irreversibility of pre-existing polluting capital. With a carbon price, the transition cost can be limited by underutilizing polluting capital, at the expense of a loss in the value of polluting assets (stranded assets) and a drop in income. In contrast, policy instruments that focus on redirecting investments -- such as feebates or environmental standards -- prevent underutilization of existing capital, avoid stranded assets, and reduce short-term losses; but they reduce emissions more slowly and increase the intertemporal cost of the transition. The paper investigates inter- and intra-generational distributional impacts and the political acceptability of climate change mitigation policy instruments. -
Publication
Investment Decision Making Under Deep Uncertainty : Application to Climate Change
(World Bank, Washington, DC, 2012-09)While agreeing on the choice of an optimal investment decision is already difficult for any diverse group of actors, priorities, and world views, the presence of deep uncertainties further challenges the decision-making framework by questioning the robustness of all purportedly optimal solutions. This paper summarizes the additional uncertainty that is created by climate change, and reviews the tools that are available to project climate change (including downscaling techniques) and to assess and quantify the corresponding uncertainty. Assuming that climate change and other deep uncertainties cannot be eliminated over the short term (and probably even over the longer term), it then summarizes existing decision-making methodologies that are able to deal with climate-related uncertainty, namely cost-benefit analysis under uncertainty, cost-benefit analysis with real options, robust decision making, and climate informed decision analysis. It also provides examples of applications of these methodologies, highlighting their pros and cons and their domain of applicability. The paper concludes that it is impossible to define the "best" solution or to prescribe any particular methodology in general. Instead, a menu of methodologies is required, together with some indications on which strategies are most appropriate in which contexts. This analysis is based on a set of interviews with decision-makers, in particular World Bank project leaders, and on a literature review on decision-making under uncertainty. It aims at helping decision-makers identify which method is more appropriate in a given context, as a function of the project's lifetime, cost, and vulnerability. -
Publication
How Inertia and Limited Potentials Affect the Timing of Sectoral Abatements in Optimal Climate Policy
(World Bank, Washington, DC, 2012-08)This paper investigates the optimal timing of greenhouse gas abatement efforts in a multi-sectoral model with economic inertia, each sector having a limited abatement potential. It defines economic inertia as the conjunction of technical inertia -- a social planner chooses investment on persistent abating activities, as opposed to choosing abatement at each time period independently -- and increasing marginal investment costs in abating activities. It shows that in the presence of economic inertia, optimal abatement efforts (in dollars per ton) are bell-shaped and trigger a transition toward a low-carbon economy. The authors prove that optimal marginal abatement costs should differ across sectors: they depend on the global carbon price, but also on sector-specific shadow costs of the sectoral abatement potential. The paper discusses the impact of the convexity of abatement investment costs: more rigid sectors are represented with more convex cost functions and should invest more in early abatement. The conclusion is that overlapping mitigation policies should not be discarded based on the argument that they set different marginal costs (`"different carbon prices"') in different sectors. -
Publication
A Cost Effective Solution to Reduce Disaster Losses in Developing Countries : Hydro-Meteorological Services, Early Warning, and Evacuation
(World Bank, Washington, DC, 2012-05)In Europe, it can be estimated that hydro-meteorological information and early warning systems save several hundreds of lives per year, avoid between 460 million and 2.7 billion Euros of disaster asset losses per year, and produce between 3.4 and 34 billion of additional benefits per year through the optimization of economic production in weather-sensitive sectors (agriculture, energy, etc.). The potential for similar benefits in the developing world is not only proportional to population, but also to increased hazard risk due to climate and geography, as well as increased exposure to weather due to the state of infrastructure. This analysis estimates that the potential benefits from upgrading to developed-country standards the hydro-meteorological information production and early warning capacity in all developing countries include: (i) between 300 million and 2 billion USD per year of avoided asset losses due to natural disasters; (ii) an average of 23,000 saved lives per year, which is valued between 700 million and 3.5 billion USD per year using the Copenhagen Consensus guidelines; and (iii) between 3 and 30 billion USD per year of additional economic benefits. The total benefits would reach between 4 and 36 billion USD per year. Because some of the most expensive components of early warning systems have already been built (e.g., earth observation satellites, global weather forecasts), these investments are relatively modest, estimated here around 1 billion US per year, reaching benefit-cost ratios between 4 and 36. -
Publication
Agreeing on Robust Decisions : New Processes for Decision Making under Deep Uncertainty
(World Bank, Washington, DC, 2014-06)Investment decision making is already difficult for any diverse group of actors with different priorities and views. But the presence of deep uncertainties linked to climate change and other future conditions further challenges decision making by questioning the robustness of all purportedly optimal solutions. While decision makers can continue to use the decision metrics they have used in the past (such as net present value), alternative methodologies can improve decision processes, especially those that lead with analysis and end in agreement on decisions. Such "Agree-on-Decision" methods start by stress-testing options under a wide range of plausible conditions, without requiring us to agree ex ante on which conditions are more or less likely, and against a set of objectives or success metrics, without requiring us to agree ex ante on how to aggregate or weight them. As a result, these methods are easier to apply to contexts of large uncertainty or disagreement on values and objectives. This inverted process promotes consensus around better decisions and can help in managing uncertainty. Analyses performed in this way let decision makers make the decision and inform them on (1) the conditions under which an option or project is vulnerable; (2) the tradeoffs between robustness and cost, or between various objectives; and (3) the flexibility of various options to respond to changes in the future. In doing so, they put decision makers back in the driver's seat. A growing set of case studies shows that these methods can be applied in real-world contexts and do not need to be more costly or complicated than traditional approaches. Finally, while this paper focuses on climate change, a better treatment of uncertainties and disagreement would in general improve decision making and development outcomes. -
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A Note on the Economic Cost of Climate Change and the Rationale to Limit it Below 2°C
(World Bank, Washington, DC, 2010-01)This note highlights a major reason to limit climate change to the lowest possible levels. This reason follows from the large increase in uncertainty associated with high levels of warming. This uncertainty arises from three sources: the change in climate itself, the change s impacts at the sector level, and their macroeconomic costs. First, the greater the difference between the future climate and the current one, the more difficult it is to predict how local climates will evolve, making it more difficult to anticipate adaptation actions. Second, the adaptive capacity of various economic sectors can already be observed for limited warming, but is largely unknown for larger changes. The larger the change in climate, therefore, the more uncertain is the final impact on economic sectors. Third, economic systems can efficiently cope with sectoral losses, but macroeconomic-level adaptive capacity is difficult to assess, especially when it involves more than marginal economic changes and when structural economic shifts are required. In particular, these shifts are difficult to model and involve thresholds beyond which the total macroeconomic cost would rise rapidly. The existence of such thresholds is supported by past experiences, including economic disruptions caused by natural disasters, observed difficulties funding needed infrastructure, and regional crises due to rapid economic shifts induced by new technologies or globalization. As a consequence, larger warming is associated with higher cost, but also with larger uncertainty about the cost. Because this uncertainty translates into risks and makes it more difficult to implement adaptation strategies, it represents an additional motive to mitigate climate change. -
Publication
Climate Change and Poverty : An Analytical Framework
(World Bank Group, Washington, DC, 2014-11)Climate change and climate policies will affect poverty reduction efforts through direct and immediate impacts on the poor and by affecting factors that condition poverty reduction, such as economic growth. This paper explores this relation between climate change and policies and poverty outcomes by examining three questions: the (static) impact on poor people's livelihood and well-being; the impact on the risk for non-poor individuals to fall into poverty; and the impact on the ability of poor people to escape poverty. The paper proposes four channels that determine household consumption and through which households may escape or fall into poverty (prices, assets, productivity, and opportunities). It then discusses whether and how these channels are affected by climate change and climate policies, focusing on the exposure, vulnerability, and ability to adapt of the poor (and those vulnerable to poverty). It reviews the existing literature and offers three major conclusions. First, climate change is likely to represent a major obstacle to a sustained eradication of poverty. Second, climate policies are compatible with poverty reduction provided that (i) poverty concerns are carefully taken into account in their design and (ii) they are accompanied by the appropriate set of social policies. Third, climate change does not modify how poverty policies should be designed, but it creates greater needs and more urgency. The scale issue is explained by the fact that climate will cause more frequent and more severe shocks; the urgency, by the need to exploit the window of opportunity given to us before climate impacts are likely to substantially increase. -
Publication
Should Marginal Abatement Costs Differ Across Sectors? The Effect of Low-Carbon Capital Accumulation
(World Bank, Washington, DC, 2013-04)The optimal timing, sectoral distribution, and cost of greenhouse gas emission reductions is different when abatement is obtained though abatement expenditures chosen along an abatement cost curve, or through investment in low-carbon capital. In the latter framework, optimal investment costs differ in each sector: they are equal to the value of avoided carbon emissions, minus the value of the forgone option to invest later. It is therefore misleading to assess the cost-efficiency of investments in low-carbon capital by comparing levelized abatement costs, that is, efforts measured as the ratio of investment costs to discounted abatement. The equimarginal principle applies to an accounting value: the Marginal Implicit Rental Cost of the Capital (MIRCC) used to abate. Two apparently opposite views are reconciled. On the one hand, higher efforts are justified in sectors that will take longer to decarbonize, such as urban planning; on the other hand, the MIRCC should be equal to the carbon price at each point in time and in all sectors. Equalizing the MIRCC in each sector to the social cost of carbon is a necessary condition to reach the optimal pathway, but it is not a sufficient condition. Decentralized optimal investment decisions at the sector level require not only the information contained in the carbon price signal, but also knowledge of the date when the sector reaches its full abatement potential.