Mitigation implications of remaining carbon budget allocation rules for Mediterranean countries

Abstract

The Mediterranean Basin is a climate change hotspot, experiencing accelerated warming and strong environmental vulnerability. Mediterranean Sea surface temperatures have increased by approximately 1.5 °C over the past four decades, underscoring the urgency of coordinated mitigation efforts. In this context, this study examines how alternative allocation criteria for distributing the remaining carbon budget compatible with the Paris Agreement (well below 2 °C) affect emission pathways among the 21 signatory countries of the Barcelona Convention. Using a mitigation pathway derived from the Global Change Analysis Model, the analysis evaluates emissions trajectories from 2030—anchored in current Nationally Determined Contributions—through 2100. Five allocation principles are assessed: Grandfathering, Per Capita, Per Capita Convergence, Equal Cumulative Per Capita, and Ability to Pay, each reflecting different trade-offs between equity and feasibility. Results indicate that, irrespective of the allocation rule, rapid and sustained decarbonisation is unavoidable. At current emission levels, the regional carbon budget would be exhausted by 2035, requiring average annual reductions of approximately 6% between 2030 and 2050 to meet global targets. While population-based criteria yield the largest regional budget and are more equitable, they imply more disruptive transitions. In contrast, emissions-based approaches are more feasible but risk reinforcing existing inequalities. These findings highlight significant implications for fossil fuel-dependent economies and stress the importance of regional cooperation. The Barcelona Convention emerges as a key platform to facilitate equitable burden-sharing and coordinated climate action in the Mediterranean region.