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. 2022 May 31;119(22):e2123536119.
doi: 10.1073/pnas.2123536119. Epub 2022 May 23.

Mitigating climate disruption in time: A self-consistent approach for avoiding both near-term and long-term global warming

Gabrielle B Dreyfus  1   2 , Yangyang Xu  3 , Drew T Shindell  4 , Durwood Zaelke  1   5 , Veerabhadran Ramanathan  6   7
Affiliations

Mitigating climate disruption in time: A self-consistent approach for avoiding both near-term and long-term global warming

Gabrielle B Dreyfus et al. Proc Natl Acad Sci U S A. .

Abstract

The ongoing and projected impacts from human-induced climate change highlight the need for mitigation approaches to limit warming in both the near term (<2050) and the long term (>2050). We clarify the role of non-CO2 greenhouse gases and aerosols in the context of near-term and long-term climate mitigation, as well as the net effect of decarbonization strategies targeting fossil fuel (FF) phaseout by 2050. Relying on Intergovernmental Panel on Climate Change radiative forcing, we show that the net historical (2019 to 1750) radiative forcing effect of CO2 and non-CO2 climate forcers emitted by FF sources plus the CO2 emitted by land-use changes is comparable to the net from non-CO2 climate forcers emitted by non-FF sources. We find that mitigation measures that target only decarbonization are essential for strong long-term cooling but can result in weak near-term warming (due to unmasking the cooling effect of coemitted aerosols) and lead to temperatures exceeding 2 °C before 2050. In contrast, pairing decarbonization with additional mitigation measures targeting short-lived climate pollutants and N2O, slows the rate of warming a decade or two earlier than decarbonization alone and avoids the 2 °C threshold altogether. These non-CO2 targeted measures when combined with decarbonization can provide net cooling by 2030 and reduce the rate of warming from 2030 to 2050 by about 50%, roughly half of which comes from methane, significantly larger than decarbonization alone over this time frame. Our analysis demonstrates the need for a comprehensive CO2 and targeted non-CO2 mitigation approach to address both the near-term and long-term impacts of climate disruption.

Keywords: climate mitigation; fossil fuel radiative forcing; near-term warming; non-CO2 climate effects; short-lived climate pollutants.

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Conflict of interest statement

The authors declare no competing interest.

Figures

Fig. 1.
Fig. 1.
Positive radiative forcing from long-lived GHGs (orange), short-lived GHGs, GHG precursors, and BC (aerosol–radiation interaction and snow albedo effects only) (yellow) and negative forcing from individual aerosol direct effects (aerosol–radiation interaction) and the total aerosol indirect effects (aerosol–cloud interaction) (separate gray pie) in (A) 2011 relative to 1750, from AR5 (14) and (B) 2019 relative to 1750, from AR6 (15). (C) The forcing at 2100 relative to 2019, under SSP3-7.0 emissions (49). Note the negative forcing due to assumed BC and CFC reduction and the positive forcing due to decline of cooling aerosols. Area of each pie chart is scaled to positive or negative forcing. See SI Appendix, Fig. S5 for bar chart version and SI Appendix, Table S6A for data.
Fig. 2.
Fig. 2.
(A) Contributions to 2019 radiative forcing from emissions by FF (CO2+non-CO2) sources and CO2 from land-use changes (Forestry and Other Land Use, FOLU CO2) compared with emissions from non-FF non-CO2 sources based on ref. and coemission factors from ref. from this study, with similar results using radiative forcing values from AR6 WGI (SI Appendix, Table S3). (B) Contribution to the 2100 radiative forcing (relative to 2019) based on future emissions in SSP3-7.0 (49) partitioned by source using coemission factors from ref. . Area of each pie chart is scaled to positive or negative forcing. Data in SI Appendix, Table S6B.
Fig. 3.
Fig. 3.
(A) Historical and future temperature projections through 2050 calculated using the RXM energy balance model based on emissions scenarios from the SSP database (49) for reference scenario (SSP3-7.0), decarbonization-driven mitigation scenario (this study), and an “decarb+targeted” scenario including aggressive decarbonization and targeted SLCP mitigation (adapted from SSP1-1.9). Historical curve (past simulated warming) is from figure SPM8.a (47, 64). (B) Rate of warming (degrees Celsius per decade) in the reference SSP3, decarbonization only, and “decarb+targeted” mitigation cases.
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