Short-Lived Promise? The Science and Policy of Cumulative and Short-Lived Climate Pollutants

Climate Dynamics Group, University of Oxford / by Myles Allen

[From Press Release]  …Author Myles Allen, Professor of Geosystem Science, spells out the difference between short-lived climate pollutants (such as methane, which has an atmospheric lifetime of about a decade) and CO2 emissions (which have an indefinite lifetime). In the paper he clarifies why comparisons between the two are misleading, and explains that short-lived climate pollutant (SLCP) reductions will have little impact on peak warming unless CO2 emissions are substantially reduced first or at the same time…

Short-Lived Promise? recommends a clear ‘peak CO2 first’ strategy:

  • Policies should recognise that near-term SLCP reductions will only affect peak warming if CO2 emissions are reduced at the same time
  • Policies must recognise that no single metric can represent both the short-term impact of SLCP emissions and the cumulative impact of CO2 emissions
  • New policies are needed to contain CO2 within the cumulative budget, which must be independent of, and in addition to, any multi-gas emission goals
  • Until CO2 emissions are falling, the need to reduce net CO2 emissions to zero overrides opportunities to offset CO2 reductions against SLCP reductions
  • As soon as CO2 emissions are falling fast enough to give a realistic prospect of meeting the cumulative budget, SLCP emission reductions should become a crucial priority to limit peak warming.

Allen concludes: “Prioritising SLCPs ahead of CO2 puts the welfare of this generation above that of the next. Reductions in both are vital, but there is no equivalent to addressing CO2, no matter how you compare different pollutants…”


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