Indicate separate contributions of long-lived and short-lived greenhouse gases in emission targets

Allen, Myles; Peters, Glen P.; Shine, Keith P.; Azar, Christian; Balcombe, Paul; Boucher, Oliviér; Cain, Michelle; Ciais, Philippe; Collins, William; Forster, Piers M.; Frame, Dave; Friedlingstein, Pierre; Fyson, Claire; Gasser, Thomas; Hare, Bill; Jenkins, Stuart; Hamburg, Steven P.; Johansson, Daniel; Lynch, John; Macey, Adrian; Morfeldt, Johannes; Nauels, Alexander; Ocko, Ilissa B.; Oppenheimer, Michael; Pacala, Stephen W.; Pierrehumbert, Raymond T.; Rogelj, Joeri; Schaeffer, Michiel; Schleußner, Carl-Friedrich; Shindell, D. T.; Skeie, Ragnhild Bieltvedt; Smith, Stephen M.; Tanaka, Katsumasa

doi:10.1038/s41612-021-00226-2

Cited by 59 publications

(49 citation statements)

References 22 publications

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“…Therefore, climate responds to long-lived greenhouse gases such as CO 2 largely in terms of their cumulative emissions, but to aerosols in direct link to its current rate of emissions. Shorter-lived greenhouse gases such as methane have an intermediate effect, whereby deep reductions in emissions can have substantial effects on temperature within a few decades (Shindell and Smith, 2019;Smith et al, 2021b;Allen et al, 2022). A further reduction in aerosol emissions -required due to their environmental and health impacts (Lelieveld et al, 2015;Cohen et al, 2017) -thus takes out the negative aerosol forcing and leads to a warming relative to the period prior to emission reduction (Brasseur and Roeckner, 2005;Dufresne et al, 2005); this effect is also known as climate penalty of air quality improvements (Ekman et al, 2020;Hong et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Robust evidence for reversal of the trend in aerosol effective climate forcing

Quaas¹,

Jia²,

Smith

et al. 2022

Atmos. Chem. Phys.

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Abstract. Anthropogenic aerosols exert a cooling influence that offsets part of the greenhouse gas warming. Due to their short tropospheric lifetime of only several days, the aerosol forcing responds quickly to emissions. Here, we present and discuss the evolution of the aerosol forcing since 2000. There are multiple lines of evidence that allow us to robustly conclude that the anthropogenic aerosol effective radiative forcing (ERF) – both aerosol–radiation interactions (ERFari) and aerosol–cloud interactions (ERFaci) – has become less negative globally, i.e. the trend in aerosol effective radiative forcing changed sign from negative to positive. Bottom-up inventories show that anthropogenic primary aerosol and aerosol precursor emissions declined in most regions of the world; observations related to aerosol burden show declining trends, in particular of the fine-mode particles that make up most of the anthropogenic aerosols; satellite retrievals of cloud droplet numbers show trends in regions with aerosol declines that are consistent with these in sign, as do observations of top-of-atmosphere radiation. Climate model results, including a revised set that is constrained by observations of the ocean heat content evolution show a consistent sign and magnitude for a positive forcing relative to the year 2000 due to reduced aerosol effects. This reduction leads to an acceleration of the forcing of climate change, i.e. an increase in forcing by 0.1 to 0.3 W m−2, up to 12 % of the total climate forcing in 2019 compared to 1750 according to the Intergovernmental Panel on Climate Change (IPCC).

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Section: Introductionmentioning

confidence: 99%

Robust evidence for reversal of the trend in aerosol effective climate forcing

Quaas¹,

Jia²,

Smith

et al. 2022

Atmos. Chem. Phys.

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“…www.annualreviews.org where κ F = c 1 is the TCRF and ρ is the RACF [ρ = c 2 /(c 1 s 2 ) in this limit], as may be verified by considering the response to a ramp forcing increase (21). Total warming is proportional to a rapid adjustment to recent forcing, averaged over the past 2s 1 years (to give an average delay of s 1 years), plus a component proportional to integrated forcing since forcing anomalies began.…”

Section: The Global Temperature Response To Radiative Forcingmentioning

confidence: 89%

Net Zero: Science, Origins, and Implications

Allen

Friedlingstein

Girardin

et al. 2022

Annu. Rev. Environ. Resour.

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This review explains the science behind the drive for global net zero emissions and why this is needed to halt the ongoing rise in global temperatures. We document how the concept of net zero carbon dioxide (CO2) emissions emerged from an earlier focus on stabilization of atmospheric greenhouse gas concentrations. Using simple conceptual models of the coupled climate–carbon cycle system, we explain why approximately net zero CO2 emissions and declining net energy imbalance due to other climate drivers are required to halt global warming on multidecadal timescales, introducing important concepts, including the rate of adjustment to constant forcing and the rate of adjustment to zero emissions. The concept of net zero was taken up through the 5th Assessment Report of the Intergovernmental Panel on Climate Change and the United Nations Framework Convention on Climate Change (UNFCCC) Structured Expert Dialogue, culminating in Article 4 of the 2015 Paris Agreement. Increasing numbers of net zero targets have since been adopted by countries, cities, corporations, and investors. The degree to which any entity can claim to have achieved net zero while continuing to rely on distinct removals to compensate for ongoing emissions is at the heart of current debates over carbon markets and offsetting both inside and outside the UNFCCC. We argue that what matters here is not the precise makeup of a basket of emissions and removals at any given point in time, but the sustainability of a net zero strategy as a whole and its implications for global temperature over multidecadal timescales. Durable, climate-neutral net zero strategies require like-for-like balancing of anthropogenic greenhouse gases sources and sinks in terms of both origin (biogenic versus geological) and gas lifetime. Expected final online publication date for the Annual Review of Environment and Resources, Volume 47 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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“…( 36 ) and recently called for by Allen et al. ( 37 ). Reporting these pollutants separately allows for consideration not only of potential effects of mitigation measures by source and implications for coemissions but also an assessment of temperature impact on multiple time horizons of interest ( 1 ).…”

Section: Contributions To Radiative Forcing: Co 2 ...mentioning

confidence: 99%

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

Dreyfus

Shindell

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Significance This study clarifies the need for comprehensive CO 2 and non-CO 2 mitigation approaches to address both near-term and long-term warming. Non-CO 2 greenhouse gases (GHGs) are responsible for nearly half of all climate forcing from GHG. However, the importance of non-CO 2 pollutants, in particular short-lived climate pollutants, in climate mitigation has been underrepresented. When historical emissions are partitioned into fossil fuel (FF)- and non-FF-related sources, we find that nearly half of the positive forcing from FF and land-use change sources of CO 2 emissions has been masked by coemission of cooling aerosols. Pairing decarbonization with mitigation measures targeting non-CO 2 pollutants is essential for limiting not only the near-term (next 25 y) warming but also the 2100 warming below 2 °C.

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Indicate separate contributions of long-lived and short-lived greenhouse gases in emission targets

Cited by 59 publications

References 22 publications

Robust evidence for reversal of the trend in aerosol effective climate forcing

Robust evidence for reversal of the trend in aerosol effective climate forcing

Net Zero: Science, Origins, and Implications

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

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