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

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.


PBL Authors
Heleen van Soest Andries Hof Michel den Elzen Detlef van Vuuren
Other authors
Nicole van den Berg
Laurent Drouet
Johannes Emmerling
Shinichiro Fujimor
Niklas Höhne
Alexandre C. Kõberle
David McCollum
Roberto Schaeffer
Swapnil Shekhar
Saritha Sudharmma
Zoi Vrontisi
Kornelis Blok
Wenying Chen


Publication title
Implications of various effort-sharing approaches for national carbon budgets and emission pathways
Publication date
14 February 2019
Publication type
Publication language
Climatic Change
pp 1–18
Product number