Carbon Emission Allocations Under an Equity Consideration

Equity has both theoretical and practical groundings in concerns for sustainability. As previously explored in the literature, equity can be used to consider how different populations,

Perfect distribution line (y = 0) — — - CEEP 2050 (y = 0.17)

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Fig. 2.9. Lorenz curves for global carbon emissions.

Perfect distribution line (y = 0) — — - CEEP 2050 (y = 0.17)

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Cumulative proportion of population

Fig. 2.9. Lorenz curves for global carbon emissions.

regions, and life forms - now and across generations - will be impacted by various environmental harms (Haughton 1999). Applied to the challenge of climate change, equity has been defined in terms of per capita GHG emissions that may safely and fairly be released by the global human population. To derive this amount, CEEP researchers first looked to the GHG emissions levels for 2050 identified in the 1990s by the IPCC as compatible with scenarios for a stabilized climate based on global carbon sink capacity (Byrne et al. 1998, p. 337). Then, this target volume for GHG emissions was divided by global population, approximately 5.2 billion people, in 1989. This calculation produced a yearly target of some 3.3 tonnes CO2 equivalent released per person (Byrne et al. 1998, p. 337), apportioned equally among the residents of all nations regardless of their economic or political power. The per person target upholds a 'democratic principle that no human being is entitled to greater access to our atmospheric commons' (Byrne et al. 2001, p. 451). However, one should note here that increases in world population since 1989 have necessitated a further reduction in the allowable amount of GHG emissions per person, causing the original target of 3.3 tonnes CO2 equivalent to fall to 2.0 tonnes by 2050.

With an equitable and sustainable emission rate in hand, the next challenge is to compare national and regional efforts to meet this rate over time. One notable method for measuring equity is the Gini coefficient (Stiglitz 1993), which is from Lorenz curves developed more than 100 years ago (Lorenz 1905) for the purpose of characterizing the extent of inequality in a community's income distribution. While the Gini coefficient has largely been used to gauge income inequality, it can be applied to measuring the inequality of carbon emissions among different nations or regions.

To plot a Lorenz curve for carbon emissions, per capita emissions were at first sorted from low to high values. Then, the percentage of total cumulative carbon emissions corresponding to the cumulative percentage of population is plotted. The derived Lorenz curves for the actual years of 1950 and 2000, as well as projected emissions under the BAU and CEEP scenarios for the year 2050, are presented in Fig. 2.9. As can be seen from this analysis, historical inequality decreased from 1950 to 2000, because non-Annex 1 emissions increased. If carbon emissions continue under the BAU scenario, inequality will continue to decline but will nonetheless be extensive in 2050 (see the discussion of Gini coefficients below). By contrast, under the CEEP scenario significant improvement will occur in the equitable distribution of carbon emissions.

After plotting the Lorenz curves, corresponding Gini (y) coefficients are derived.10 In 1950, y was 0.79, which indicates that vast inequality in per capita carbon emissions existed at a global scale. In 2000, y was reduced to 0.58, still indicating significant inequality. Under the BAU scenario, the Gini coefficient by 2050 will reach 0.43, indicating some improvement yet still failing to reach a more equitable allocation of emissions among nations. If the CEEP scenario is followed, by 2050 y will have significantly decreased, reaching 0.17.

Thus, three distinct pathways exist toward equity, albeit 'equity' of very different types. The shift in the Lorenz curve from 1950 to 2000 depicts an increase in equity resulting from higher overall GHG emissions throughout the world, where developing nations have begun to increase their emissions toward the significant scale of releases demonstrated by industrialized countries. The Lorenz curve shift from 2000 to the BAU 2050 scenario portrays a world where equity increases because of higher non-Annex 1 emissions, while world emissions overall reach a plateau. In both instances, equity improvement occurs without corresponding progress in sustainability. In fact, both the historical and BAU cases increase warming risk, with the BAU path doing so at alarming levels (leading to CO2 concentrations of more than 710 ppm by 2100). By contrast, the shift from 2000 to the CEEP 2050 scenario represents a type of equity under which non-Annex 1 nations at first emit increasing amounts of GHGs, while Annex 1 countries simultaneously achieve significant cuts. Importantly, aggregated global emissions - to include non-Annex 1 actors - fall to sustainable levels by 2050 and avert warming risk by the end of the century.

In this regard, the CEEP scenario achieves equity of national effort to realize climate sus-tainability, while the BAU case achieves neither. This underscores a key finding: it is not possible to avert warming risk if unequal efforts to reduce CO2 emissions are maintained. The implication of this finding is next explored for the case of the largest CO2 emitter in the world - the US - and the decision to date of its national government to refuse participation in global accord to cut emissions.

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