Letter | Published:

New use of global warming potentials to compare cumulative and short-lived climate pollutants

Nature Climate Change volume 6, pages 773776 (2016) | Download Citation

Abstract

Parties to the United Nations Framework Convention on Climate Change (UNFCCC) have requested guidance on common greenhouse gas metrics in accounting for Nationally determined contributions (NDCs) to emission reductions1. Metric choice can affect the relative emphasis placed on reductions of ‘cumulative climate pollutants’ such as carbon dioxide versus ‘short-lived climate pollutants’ (SLCPs), including methane and black carbon2,3,4,5,6. Here we show that the widely used 100-year global warming potential (GWP100) effectively measures the relative impact of both cumulative pollutants and SLCPs on realized warming 20–40 years after the time of emission. If the overall goal of climate policy is to limit peak warming, GWP100 therefore overstates the importance of current SLCP emissions unless stringent and immediate reductions of all climate pollutants result in temperatures nearing their peak soon after mid-century7,8,9,10, which may be necessary to limit warming to “well below 2 °C” (ref. 1). The GWP100 can be used to approximately equate a one-off pulse emission of a cumulative pollutant and an indefinitely sustained change in the rate of emission of an SLCP11,12,13. The climate implications of traditional CO2-equivalent targets are ambiguous unless contributions from cumulative pollutants and SLCPs are specified separately.

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Acknowledgements

M.R.A. was supported by the Oxford Martin Programme on Resource Stewardship. M.R.A. and K.P.S. received support from the UK Department of Energy and Climate Change under contract no. TRN/307/11/2011; J.S.F. from the Norwegian Research Council, project no. 235548; R.T.P. from the Kung Carl XVI Gustaf 50-års fond; P.M.F. from the UK Natural Environment Research Council grant no. NE/N006038/1. The authors would like to thank numerous colleagues, particularly among IPCC authors, for discussions of metrics over recent years, and J. Cook for encouraging this work.

Author information

Affiliations

  1. Environmental Change Institute, School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK

    • Myles R. Allen
  2. Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK

    • Myles R. Allen
    •  & Raymond T. Pierrehumbert
  3. Center for International Climate and Environmental Research - Oslo (CICERO), PO Box 1129 Blindern, 0318 Oslo, Norway

    • Jan S. Fuglestvedt
  4. Department of Meteorology, University of Reading, Earley Gate, PO Box 243, Reading RG6 6BB, UK

    • Keith P. Shine
  5. New Zealand Agricultural Greenhouse Gas Research Centre, Private Bag 11008, Palmerston North 4442, New Zealand

    • Andy Reisinger
  6. School of Earth and Environment, Maths/Earth and Environment Building, The University of Leeds, Leeds LS2 9JT, UK

    • Piers M. Forster

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Contributions

M.R.A. conceived and led the study; all authors contributed to extensive discussions, analysis, interpretation and writing of the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Myles R. Allen.

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DOI

https://doi.org/10.1038/nclimate2998

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