Implications of various effort-sharing approaches for national carbon budgets and emission pathways

Nicole J Van Den Berg,Heleen L Van Soest,Zoi Vrontisi,Wenying Chen,Saritha Sudharmma Vishwanathan,Detlef P Van Vuuren,Shinichiro Fujimori,Michel G J Den Elzen,Kornelis Blok,David Mccollum,Johannes Emmerling,Laurent Drouet,Niklas Höhne,Andries F Hof,Roberto Schaeffer,Alexandre C Kõberle,Swapnil Shekhar

doi:10.1007/s10584-019-02368-y

Abstract

The bottom-up approach of the Nationally Determined Contributions (NDCs) in the Paris Agreement has led countries to self-determine their greenhouse gas (GHG) emission reduction targets. The planned ‘ratcheting-up’ process, which aims to ensure that the NDCs comply with the overall goal of limiting global average temperature increase to well below 2 °C or even 1.5 °C, will most likely include some evaluation of ‘fairness’ of these reduction targets. In the literature, fairness has been discussed around equity principles, for which many different effort-sharing approaches have been proposed. In this research, we analysed how country-level emission targets and carbon budgets can be derived based on such criteria. We apply novel methods directly based on the global carbon budget, and, for comparison, more commonly used methods using GHG mitigation pathways. For both, we studied the following approaches: equal cumulative per capita emissions, contraction and convergence, grandfathering, greenhouse development rights and ability to pay. As the results critically depend on parameter settings, we used the wide authorship from a range of countries included in this paper to determine default settings and sensitivity analyses. Results show that effort-sharing approaches that (i) calculate required reduction targets in carbon budgets (relative to baseline budgets) and/or (ii) take into account historical emissions when determining carbon budgets can lead to (large) negative remaining carbon budgets for developed countries. This is the case for the equal cumulative per capita approach and especially the greenhouse development rights approach. Furthermore, for developed countries, all effort-sharing approaches except grandfathering lead to more stringent budgets than cost-optimal budgets, indicating that cost-optimal approaches do not lead to outcomes that can be regarded as fair according to most effort-sharing approaches.

Highlights

As part of the Paris Agreement, almost all countries agreed to focus international climate policy on reducing greenhouse gas (GHG) emissions in order to limit the increase ofThis article is part of a Special Issue on 'National Low-Carbon Development Pathways' edited by Roberto Schaeffer, Valentina Bosetti, Elmar Kriegler, Keywan Riahi, Detlef van Vuuren, and John Weyant
The most salient results are the extreme outcomes of the greenhouse development rights’ (GDR)* approach relative to all other approaches
This research compared different methods and parameterisations of allocating carbon budgets and reduction targets in emission pathways based on effort-sharing approaches for different equity principles

Summary

Introduction

As part of the Paris Agreement, almost all countries agreed to focus international climate policy on reducing greenhouse gas (GHG) emissions in order to limit the increase ofThis article is part of a Special Issue on 'National Low-Carbon Development Pathways' edited by Roberto Schaeffer, Valentina Bosetti, Elmar Kriegler, Keywan Riahi, Detlef van Vuuren, and John Weyant. The agreement allows countries to formulate their own national targets in the form of Nationally Determined Contributions (NDCs). This means that the evaluation of the NDC targets is needed in order to ensure that their combined effort leads to the overall objective of the agreement. This evaluation is referred to as the stocktaking process. Discussions regarding the ‘fair’ contribution of countries have been ongoing since the United Nations Framework Convention on Climate Change (UNFCCC) Article 3 in 1992, specifying that the climate system should be protected ‘in accordance with their common but differentiated responsibilities and respective capability’ (UNFCCC 1992). An extensive literature has emerged using equity principles such as ‘responsibility’, ‘capability’, ‘equality’ and ‘sovereignty’ (Clarke et al 2014; Höhne et al 2014) as the basis for several effort-sharing approaches

Methods

Results

Conclusion