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International climate policy

The path to 1.5 °C requires ratcheting of climate pledges

Increasing climate ambition through 2030 will be crucial to limiting global peak temperature changes this century. Countries need to ratchet their 2030 pledges made in Glasgow to reduce temperature overshoot and consequently reduce the risks of irreversible and adverse consequences to natural and human systems.

Messages for policy

  • Ratcheting near-term ambition to 2030 as called for by the Glasgow Climate Pact can help to reduce peak temperature change and bring us closer to the Paris Agreement’s 1.5 °C temperature goal.

  • Delaying ratcheting of ambition to beyond 2030 could still limit end-of-century temperature change to below 1.5 °C but would result in higher temperature overshoot over many decades.

  • Ratcheting near-term ambition could also facilitate faster transitions to net-zero emissions systems, especially in major economies.

  • Ratcheting near-term ambition could lay strong institutional infrastructures required to phase out fossil fuels and incentivize research and development, and to deploy more nascent technologies.

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Fig. 1: Temperature change outcomes of the emissions pathways explored in Iyer et al. (2022).

Further Reading

  • Ou, Y. et al. Can updated climate pledges limit warming well below 2 °C? Science 374, 693–695 (2021). This study modelled (as stated) the unconditional pledges for 2030, long-term strategies and net-zero targets submitted by countries until 30 September 2021 in preparation for COP26 held in Glasgow in November 2021. It also explored their long-term probabilistic temperature implications.

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  • Meinshausen, M. et al. Realization of Paris Agreement pledges may limit warming just below 2 °C. Nature 604, 304–309 (2022). This study modelled all conditional and unconditional pledges for 2030, long-term strategies and net-zero targets, including those submitted to the end of COP26 (that includes submissions beyond those considered in Ou, Y. et al. (2021)) and explored their long-term temperature outcomes.

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  • Dooley, K. et al. Ethical choices behind quantifications of fair contributions under the Paris Agreement. Nat. Clim. Change 11, 300–305 (2021). This study reviewed different climate effort-sharing assessments and presents guidelines for developing and adjudicating policy-relevant (but not ethically neutral) equity research.

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  • Riahi, K. et al. Cost and attainability of meeting stringent climate targets without overshoot. Nat. Clim. Change 11, 1063–1069 (2021). This study explored emissions pathways with accelerated transition towards net-zero CO2 emissions with limited temperature overshoot.

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  • Emissions Gap Report 2021: The Heat is On – A World of Climate Promises Not Yet Delivered (United Nations Environment Programme, 2021). This report presents the gap or difference between emissions, assuming that countries were to achieve their pledges to 2030 and the emissions level consistent with pathways that limit long-term global warming to less than 1.5 °C.

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The research described in this paper was conducted with support from the US Environmental Protection Agency IAA DW-089-92460001 (G.I., Y.O., J.E., J.F., S.W. and H.M.). 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 or the US Government, and no official endorsement should be inferred.

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G.I. and Y.O. contributed equally to this study.

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Correspondence to Haewon McJeon.

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The authors declare no competing interests.

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Iyer, G., Ou, Y., Edmonds, J. et al. The path to 1.5 °C requires ratcheting of climate pledges. Nat. Clim. Chang. 12, 1092–1093 (2022).

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