温室气体排放的贫困成本

Policy Research Working Paper The Poverty Cost of Greenhouse Gas Emissions Stephane HallegatteDaniel Gerszon MahlerBenoit Decerf Policy Research Working Paper11316 Abstract Economic growth is the key driver of poverty reduction. Atthe same time, economic growth still increases greenhousegas emissions, which are expected to increase poverty in thefuture. To quantify the combined effect of these two mech-anisms, this paper introduces emissions-adjusted poverty, anew measure that sums a country’s poverty with the futureglobal poverty that the country’s emissions will create. The The paper estimates that each kiloton of carbon dioxideemitted today adds two person-years of extreme povertyglobally between now and 2100. Despite large uncertainties,the paper identifies two robust insights. For poor countries,poverty reduction from economic growth outweighs futureglobal poverty added from the emissions associated withthis growth, even with historical carbon intensities. In con-trast, for many rich countries, the climate-related cost of The Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about developmentissues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry thenames of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely those The Poverty Cost of Greenhouse Gas Emissions Stephane HallegatteⓡDaniel Gerszon MahlerⓡBenoit Decerf Keywords:Poverty, greenhouse gas emissions, economic growth, social cost of carbon, climate JEL codes:Q54, I32, O44, Q51, D63, Q56 Introduction Reducing poverty and protecting human prosperity from climate change are two majorglobal policy challenges. Recent technological developments and stubborn market failuresoffer opportunities to make progress on both fronts. For example, renewable power createsnew opportunities to connect poor people to electricity at lower cost than fossil fuels.1–3As But since economic growth is the largest driver of poverty reduction4,5and is still associatedwith higher GHG emissions, there is also a tension between these two challenges: economicgrowth reduces poverty over the short term while its greenhouse gas emissions increasetemperatures and adversely affect futureglobal poverty.6,7Such a tension appears even Navigating the tension in a consistent way and monitoring the overall progress achievedrequires an indicator that meaningfully reflects bothchallenges. One key desideratum forsuch an indicator is its ease of communication and simplicity. A black box indicator excludes We introduce emissions-adjusted poverty, which combines poverty and emissions. Thisindicator sums a country’s current per capita poverty with the future global poverty that thecountry’s current per capita emissions are expected to generate between now and the end Emissions-adjusted poverty depends on a parameter,𝛾𝛾𝑡𝑡, which captures the rate at whichcurrent emissions are expected to generate future poverty. The parameter𝛾𝛾𝑡𝑡expresses thecost of current emissions, but rather than expressing it in monetary units, it does so in termsof “years of poverty.” The value for𝛾𝛾𝑡𝑡informs on the reduction in current poverty that is needed to “compensate” for an increase in emissions. Concretely, if a reform generates an Parameter𝛾𝛾𝑡𝑡is related to the Social Cost of Carbon (SCC), which expresses the futureeconomic damage caused by one ton of CO2.10The keydifferenceis that while the SCCattributes equal weight to a dollar lost to a wealthy person and a poor person,𝛾𝛾𝑡𝑡prioritizes their livelihoods. In addition,𝛾𝛾𝑡𝑡makes the cost of emissions more human centric byexpressing them in terms of years spent in poverty instead of dollars lost. Parameter𝛾𝛾𝑡𝑡is a special case of (and shares the same conceptual foundation with) theequity-weighted SCC, which uses distributional weights to adjust the SCC to give more importance to impacts on the poorest.11–14While the equity-weighted SCC is conceptuallysolid, one key challenge is that communicating it to non-experts is difficult. The limitedcommunicabilityis shared with other distribution-sensitive welfare functions.15 Ourapproach and parameter deliberately rely on a cruder concept of social welfare, making iteasier to communicate. We do so by using a binary approach with a poverty line (either oneis poor or not) instead of the more complex elasticity of marginal utility. We communicate Our paper is related to studies that calculate the non-economic impacts of marginalemissions. Past papers have calculated the mortality costs of one unit of carbon,16the cropprotection lost per degree of warming,17and the marginal effects of a ton of CO2on glacial Emissions-adjusted poverty Formally, emissions-adjusted poverty (𝐸𝐸𝐸𝐸𝐸𝐸) in country𝑗𝑗in year𝑡𝑡is defined as where𝑁𝑁is the number of