The impact of policy and model uncertainties on emissions projections of the Paris Agreement pledges

Michel G J den Elzen, Ioannis Dafnomilis, Andries F. Hof, Marika Olsson, Arthur Beusen, W J Wouter Botzen, Takeshi Kuramochi, Leonardo Nascimento, Joeri Rogelj

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Tracking progress towards the Paris Agreement climate goal requires understanding the 2030 emission levels implied by countries' National Determined Contributions (NDCs). However, key uncertainties and assumptions impact greenhouse gas (GHG) emission projections implied by the NDCs. This study analyses this impact, both globally and for major emitting countries. We find that the assessed uncertainties markedly affect global GHG emission projections. Full achievement of NDC targets is estimated to result in a range of 46-60 GtCO2eq by 2030 (median estimate: 53 GtCO2eq). The uncertainty in measuring historical emissions, including land-use, as reflected by different datasets is the most important contributing factor. This is followed by two equally important factors globally: socio-economic baseline uncertainty and uncertainty about the emissions implied by current policies in case NDCs are less ambitious than these. Overall, the impact of policy uncertainty (i.e. uncertainty resulting from conditionality of or ranges in NDC targets and uncertainty in emissions resulting from current policies) is about equally important as model/technical uncertainty (i.e. uncertainty in historical emissions and socio-economic baseline variations). This new insight is important for decision makers and researchers because a larger share of the total uncertainty is now attributable to aspects that can be influenced by policy decisions compared to previous analyses of NDC uncertainty.
Original languageEnglish
Article number054026
Number of pages13
JournalEnvironmental Research Letters
Volume18
Issue number5
DOIs
Publication statusPublished - 1 May 2023

Bibliographical note

Funding Information:
This work is supported by the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 821471: ENGAGE). We thank all colleagues involved, in particular Maarten van den Berg, Niklas Höhne, Elena Hooijschuur and Mark Roelfsema for their input and comments.

Publisher Copyright:
© 2023 The Author(s). Published by IOP Publishing Ltd

Keywords

  • NDC
  • Paris Agreement
  • climate change mitigation
  • climate policy
  • integrated assessment models
  • uncertainty

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