Attributing long-term sea-level rise to Paris Agreement emission pledges

Alexander Nauels; Johannes Gütschow; Matthias Mengel; Malte Meinshausen; Peter U. Clark; Carl-Friedrich Schleussner

doi:10.1073/pnas.1907461116

New Research In

Edited by Arild Underdal, University of Oslo, Oslo, Norway, and approved September 19, 2019 (received for review April 30, 2019)

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Significance

Sea-level rise poses a threat to coastal areas and will continue for centuries, even after global mean temperature has stabilized. Research assessing the implications of current international climate mitigation efforts usually focuses on 21st century climate impacts. The multicentennial sea-level rise commitment of pledged near-term emission reduction efforts under the Paris Agreement has not been quantified yet. We here estimate this sea-level rise commitment and find that pledged emissions until 2030 lock in 1-m sea-level rise in the year 2300. Our analysis highlights the defining role of present-day emissions for future sea-level rise and points to the potential of reducing the long-term sea-level-rise commitment by more ambitious national emission reduction targets.

Abstract

The main contributors to sea-level rise (oceans, glaciers, and ice sheets) respond to climate change on timescales ranging from decades to millennia. A focus on the 21st century thus fails to provide a complete picture of the consequences of anthropogenic greenhouse gas emissions on future sea-level rise and its long-term impacts. Here we identify the committed global mean sea-level rise until 2300 from historical emissions since 1750 and the currently pledged National Determined Contributions (NDC) under the Paris Agreement until 2030. Our results indicate that greenhouse gas emissions over this 280-y period result in about 1 m of committed global mean sea-level rise by 2300, with the NDC emissions from 2016 to 2030 corresponding to around 20 cm or 1/5 of that commitment. We also find that 26 cm (12 cm) of the projected sea-level-rise commitment in 2300 can be attributed to emissions from the top 5 emitting countries (China, United States of America, European Union, India, and Russia) over the 1991–2030 (2016–2030) period. Our findings demonstrate that global and individual country emissions over the first decades of the 21st century alone will cause substantial long-term sea-level rise.

Footnotes

↵¹To whom correspondence may be addressed. Email: alex.nauels{at}climateanalytics.org.

Author contributions: A.N. and C.-F.S. designed research; A.N. and J.G. performed research; A.N. and J.G. analyzed data; and A.N., J.G., M. Mengel, M. Meinshausen, P.U.C., and C.-F.S. wrote the paper.
The authors declare no competing interest.
This article is a PNAS Direct Submission.
Data deposition: Pathway as well as projection data and code to reproduce the results shown in this study can be accessed at: https://gitlab.com/anauels/ndc_slr_attribution.
See Commentary on page 23373.

This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

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