Can updated climate pledges limit warming well below 2°C?
Abstract
As part of the 2015 Paris Agreement, countries agreed to regularly revisit and enhance their national climate strategies and, every 5 years, to offer new emissions targets in the form of nationally determined contributions (NDCs) (1). This year’s 26th Conference of Parties provides a waypoint in this updating process as countries have been offering enhanced or completely new NDCs (2, 3) (henceforth, updated pledges) (4). We find that compared with the 2015 pledges, the updated pledges suggest a strengthening of ambition through 2030. By calculating probabilistic temperature outcomes over the 21st century for five emissions scenarios (see the figure and table S1), we find that the updated pledges provide a stronger near-term foundation to deliver on the long-term goals of the Paris Agreement of reducing the probability of the worst levels of temperature change this century and increasing the likelihood of limiting temperature change to well below 2°C.
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Supplementary Materials
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science.org/doi/10.1126/science.abl8976
References and Notes
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J. Rogelj et al., in “Global warming of 1.5°C: An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty,” V. Masson-Delmotte et al., Eds. (Intergovernmental Panel on Climate Change, 2018).
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Copyright
Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.
History
Published online: 4 November 2021
Acknowledgments
Y.O. and G.I. contributed equally to this work. The views and opinions expressed in this paper are those of the authors alone and do not necessarily state or reflect those of the Environmental Protection Agency, the Department of State, or the US government, and no official endorsement should be inferred. Current policy projections and update pledges used in this analysis were derived by Climate Action Tracker, with thanks to all project team members who contributed. Funding: This work was funded by US Environmental Protection Agency IAA DW-089-92460001 (Y.O., G.I., M.B., J.E., P.P., S.Y., S.W., and H.M.) and German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety grant 16_I_291_Global_A_CAT (C.F., A.G., S.G.-Z., M.J.G., N.H., L.J., and T.K.). Data and materials availability: GCAM is an open -source community model available at https://github.com/JGCRI/gcam-core/releases. Source code and data associated with this analysis are available at https://doi.org/10.5281/zenodo.5553171.
