Fair and Cost-effective Effort-Sharing under the Paris Agreement

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The door is open for a significant change in the way we live.
Source: Olivier Le Moal / Fotolia.com

The Paris Agreement has strengthened objectives to limit global warming remarkably. Considering a fair or cost-effective contribution to global efforts relevant greenhouse gas emitting countries should upgrade their national 2030 commitments to comply with the respective goals. Even, simply redistributing cost-effective reductions among parties by 2050 would not meet fairness considerations.

Given that the Paris Agreement (PA) has strengthened the long-term temperature goal and that it calls for a balance of greenhouse gas (GHG) emissions and sinks within the 21st century, there is the urgent need to re-assess the climate targets worldwide. On top of that, the PA stresses that contributions from the states have to reflect “the highest possible ambition” and “respective capabilities”.

This study has derived national GHG emissions reduction contributions for 2030 and 2050 that are consistent with the Paris Agreements’ long-term temperature goal, both based on fairness (Climate Action Tracker, 2018) and cost-effectiveness (EN-ERDATA, 2018) approaches. The comparison of these approaches yields insights whether or not a country can or should in-crease the ambition of its nationally determined contributions (NDC). The data can also be taken to show how large the efforts in the country domestically should be and to indicate the need for support to or from other countries. 

The analysis focuses on countries that are particularly relevant because of their share in global GHG emissions and their role in international climate policy, namely Brazil, Canada, China, the EU, India, Japan the United States of America, and Germany respectively. The analysis reveals for both approaches, that the more ambitious long-term temperature goal of the Paris Agreement results in substantially higher reduction requirements for all countries compared to the former Cancun targets. Given that there has already been a gap between NDCs and the Cancun target of holding global warming below 2°C, the Paris goals call for even more ambitious emissions reduction goals in their respective NDCs. For the EU, the gap between its NDC and a 1.5°C-consistent pathway is about 28 %. This shows the clear need to reconsider the EU’s 2030 target in light of the Paris Agreement. A look at 1.5°C-compatible emissions pathways further shows that in the longer term up to 2050, the fairness-based emissions allowances in the major emitting countries considered cannot be met by redistributing the reductions of a cost-effective pathway among each other. This suggests that for compatibility with the more ambitious temperature goal of the Paris Agreement, it will also become even more important to have a truly global international cooperation on climate change mitigation. 

In spite of the need for international cooperation, it needs to be re-emphasized that the GHG emissions reductions attributed to the domestic targets in the current NDCs for all countries under study here do not meet the level of emissions reductions required for a global cost-effective pathway, even with regard to compatibility with the “old” Cancun 2°C goal. Therefore, a substantial increase of ambition in all the countries under study is possible without deviating from a global cost-effective pathway. Even if the high uncertainty about the development of mitigation costs is taken into account, the order of the existing gap justifies no hesitation about moving beyond the ambition of the current NDCs.