International CO2 emissions distribution analysis from integrated assessment models

Aims: Inequality in greenhouse gas emissions distribution among world countries is a focus variable for the design of future international agreements to tackle global warming. Taking distribution problems properly into account in policy design leads to an increase in the perceived fairness of the measures and facilitates widespread participation. In the recent debate about the future design of post-Kyoto agreements, developing countries’ objection about their participation to global environmental agreements lies on the fact that in the past the geographical distribution of emissions was quite unequal and addressed towards developed countries. Conversely developed countries point out that if developing countries did not join the Kyoto Protocol the abatement effort would be unequal and the effectiveness of the policy would be weak. These thoughts let us conclude that equality in the distribution of emissions is one of the most important issues in world negotiations of environmental agreements. Methodology: This work specifically analyses distributional aspects of CO2 emissions. Whereas our analysis is implemented by tools (inequality indices and decomposition analyses) which are typically applied in income distribution analyses and the social choice literature, a methodological novelty is that our study is driven by data of simulations deriving from many optimal growth integrated assessment models (IAMs) characterised by different frameworks in future scenarios. IAMs have been quite seldom used to analyse distributional issues of climate change but they represent very interesting analysis tools. First, they are very sophisticated so that they can capture complexities. Second, they are models including an environmental feedback to the economy when many past contributions include a framework in which the economic variables affect the environmental indicators, without incorporating the opposite effect. Notwithstanding IAMs represent a very interesting tool to gain information about the future evolution of global warming their limit is that they are based on parameters and assumptions which affect the reliability of results. However no many contributions implement a models comparison to test robustness of findings and to highlight the effect generated by specific hypotheses underlying different theoretical frameworks. An original contribution coming from our research is that we use techniques to analyse inequality in the distribution of CO2 emissions (in terms of path, composition and sources of inequality) which have never been applied in the context of IAMs comparison and for data coming from simulations in a field of research where previous studies mainly worked with empirical data (Padilla and Serrano 2006, Duro and Padilla 2006, Duro and Padilla 2008) or with only one IAM (Cantore and Padilla 2007). Results: By sharing an interdisciplinary approach we find in a wide set of scenarios representing future emissions stabilizing policies that inequality in terms of GDP arising between rich and poor regions will mainly compose inequality in emissions distribution but no solid evidence that policy addressed to the level or distribution of income could be safely implemented to govern global warming distributional aspects in the long run. This work poses the basis for further research aimed at verifying and studying more in depth our findings and at seeking effective solutions to drive distributional aspects of climate change for policy makers.