Energy budget constraints on historical radiative forcing

Andrews, Timothy; Forster, Piers M.

doi:10.1038/s41558-020-0696-1

Cited by 18 publications

(23 citation statements)

References 49 publications

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“…This ERF is a little lower than the equivalent estimate from HadGEM3-GA7.1, which was 1.81 W m −2 . The UKESM1 estimate is also lower than the median estimate from CMIP5 models assessed in AR5, which equates to approximately 1.9 W m −2 after adjustment to the reference period of 1861-1880 to 2010-2011 (Andrews and Forster, 2020). AR5 also provided an overall central estimate of 2.2 W m −2 and a 5 %-95 % confidence range of 1.0 to 3.2 W m −2 (after adjustment to the same reference period as above in Andrews and Forster, 2020) taking into account multiple streams of evidence.…”

Section: Total Anthropogenic Erfmentioning

confidence: 69%

“…The UKESM1 estimate is also lower than the median estimate from CMIP5 models assessed in AR5, which equates to approximately 1.9 W m −2 after adjustment to the reference period of 1861-1880 to 2010-2011 (Andrews and Forster, 2020). AR5 also provided an overall central estimate of 2.2 W m −2 and a 5 %-95 % confidence range of 1.0 to 3.2 W m −2 (after adjustment to the same reference period as above in Andrews and Forster, 2020) taking into account multiple streams of evidence. Andrews and Forster (2020) re-evaluated this as 2.3 W m −2 with a narrower range of 1.7-3.0 W m −2 [5 %-95 % confidence] using a combination of atmospheric model outputs and observational constraints.…”

Section: Total Anthropogenic Erfmentioning

confidence: 69%

“…The net anthropogenic ERF is 1.76 ± 0.04 W m −2 , again consistent with the range of estimates from AR5 (Myhre et al, 2013a) and the estimate from HadGEM3-GC3.1 (1.81 W m −2 ; . The net anthropogenic ERF quantified here is also narrowly inside the range of net anthropogenic ERF of 2.3 W m −2 (1.7 to 3.0 W m −2 ; 5 %-95 % confidence interval) derived from a top-down energy budget constraint based on measurements of historical global mean temperature change, the Earth's heat uptake, and model estimates of the Earth's radiative response (Andrews and Forster, 2020).…”

Section: Overview Of Erfsmentioning

confidence: 72%

“…Myhre et al, 2013a). Participating models in the 5th Coupled Model Intercomparison Project (CMIP5; Taylor et al, 2012) can show large differences in CO 2 forcing (Andrews et al, 2012a;Forster et al, 2013) due to model diversity and/or calculation method. For example, the RF attributed to long-lived greenhouse gases (LLGHGs) is typically based on changes in observed concentrations between the pre-industrial (PI) and the present-day (PD) periods and uses line-by-line radiative transfer calculations and/or simple, yet justified, expressions for RF based on, e.g.…”

Section: Introductionmentioning

confidence: 99%

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Assessment of pre-industrial to present-day anthropogenic climate forcing in UKESM1

et al. 2021

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Abstract. Quantifying forcings from anthropogenic perturbations to the Earth system (ES) is important for understanding changes in climate since the pre-industrial (PI) period. Here, we quantify and analyse a wide range of present-day (PD) anthropogenic effective radiative forcings (ERFs) with the UK's Earth System Model (ESM), UKESM1, following the protocols defined by the Radiative Forcing Model Intercomparison Project (RFMIP) and the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP). In particular, quantifying ERFs that include rapid adjustments within a full ESM enables the role of various chemistry–aerosol–cloud interactions to be investigated. Global mean ERFs for the PD (year 2014) relative to the PI (year 1850) period for carbon dioxide (CO2), nitrous oxide (N2O), ozone-depleting substances (ODSs), and methane (CH4) are 1.89 ± 0.04, 0.25 ± 0.04, −0.18 ± 0.04, and 0.97 ± 0.04 W m−2, respectively. The total greenhouse gas (GHG) ERF is 2.92 ± 0.04 W m−2. UKESM1 has an aerosol ERF of −1.09 ± 0.04 W m−2. A relatively strong negative forcing from aerosol–cloud interactions (ACI) and a small negative instantaneous forcing from aerosol–radiation interactions (ARI) from sulfate and organic carbon (OC) are partially offset by a substantial forcing from black carbon (BC) absorption. Internal mixing and chemical interactions imply that neither the forcing from ARI nor ACI is linear, making the aerosol ERF less than the sum of the individual speciated aerosol ERFs. Ozone (O3) precursor gases consisting of volatile organic compounds (VOCs), carbon monoxide (CO), and nitrogen oxides (NOx), but excluding CH4, exert a positive radiative forcing due to increases in O3. However, they also lead to oxidant changes, which in turn cause an indirect aerosol ERF. The net effect is that the ERF from PD–PI changes in NOx emissions is negligible at 0.03 ± 0.04 W m−2, while the ERF from changes in VOC and CO emissions is 0.33 ± 0.04 W m−2. Together, aerosol and O3 precursors (called near-term climate forcers (NTCFs) in the context of AerChemMIP) exert an ERF of −1.03 ± 0.04 W m−2, mainly due to changes in the cloud radiative effect (CRE). There is also a negative ERF from land use change (−0.17 ± 0.04 W m−2). When adjusted from year 1850 to 1700, it is more negative than the range of previous estimates, and is most likely due to too strong an albedo response. In combination, the net anthropogenic ERF (1.76 ± 0.04 W m−2) is consistent with other estimates. By including interactions between GHGs, stratospheric and tropospheric O3, aerosols, and clouds, this work demonstrates the importance of ES interactions when quantifying ERFs. It also suggests that rapid adjustments need to include chemical as well as physical adjustments to fully account for complex ES interactions.

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Section: Total Anthropogenic Erfmentioning

confidence: 69%

Section: Total Anthropogenic Erfmentioning

confidence: 69%

Section: Overview Of Erfsmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Assessment of pre-industrial to present-day anthropogenic climate forcing in UKESM1

et al. 2021

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show abstract

“…This ERF is a little lower than the equivalent estimate from HadGEM3-GA7.1, which was 1.81 W m -2 . The UKESM1 estimate is also somewhat lower than the median estimate from CMIP5 models assessed in AR5, which equates to approximately 1.9 W m -2 after adjustment to the reference period of 1861-1880 to 2010-11 (Andrews and Forster, 2019;hereafter AF19). AR5 also provided an overall central estimate of 2.2 W m -2 and a 5-95 % confidence range of 1.0 -3.2 W m -2 (after adjustment to the same reference period as above in AF19) taking into account multiple streams of evidence.…”

Section: Total Anthropogenic Erfmentioning

confidence: 71%

Assessment of pre-industrial to present-day anthropogenic climate forcing in UKESM1

O’Connor¹,

Abraham²,

Dalvi³

et al. 2020

Preprint

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Abstract. Quantifying forcings from anthropogenic perturbations to the Earth System (ES) is important for understanding changes in climate since the pre-industrial period. In this paper, we quantify and analyse a wide range of present-day (PD) anthropogenic climate forcings with the UK's Earth System Model (ESM), UKESM1, following the protocols defined by the Radiative Forcing Model Intercomparison Project (RFMIP) and the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP). In particular, by quantifying effective radiative forcings (ERFs) that include rapid adjustments within a full ESM, it enables the role of various climate-chemistry-aerosol-cloud feedbacks to be quantified. Global mean ERFs are 1.83, 0.13, &#8722;0.33, and 0.93&#8201;W&#8201;m&#8722;2 at the PD (Year 2014) relative to the pre-industrial (PI; Year 1850) for carbon dioxide, nitrous oxide, ozone-depleting substances, and methane, respectively. The PD total greenhouse gas ERF is 2.89&#8201;W&#8201;m&#8722;2, larger than the sum of the individual GHG ERFs. UKESM1 has an aerosol forcing of &#8722;1.13&#8201;W&#8201;m&#8722;2. A relatively strong negative forcing from aerosol-cloud interactions and a small negative instantaneous forcing from aerosol-radiation interactions are partially offset by a substantial forcing from black carbon absorption. Internal mixing and chemical interactions mean that neither the forcing from aerosol-radiation interactions nor aerosol-cloud interactions are linear, making the total aerosol ERF less than the sum of the individual speciated aerosol ERFs. Tropospheric ozone precursors, in addition to exerting a positive forcing due to ozone, lead to oxidant changes which in turn cause an indirect aerosol ERF, altering the sign of the net ERF from nitrogen oxide emissions. Together, aerosol and tropospheric ozone precursors (near-term climate forcers, NTCFs) exert a global mean ERF of &#8722;1.12&#8201;W&#8201;m&#8722;2, mainly due to changes in the cloud radiative effect. There is also a negative PD ERF from land use (&#8722;0.32&#8201;W&#8201;m&#8722;2). It is outside the range of previous estimates, and is most likely due to too strong an albedo response. In combination, the net anthropogenic ERF is potentially biased low (1.61&#8201;W&#8201;m&#8722;2) relative to other estimates, due to the inclusion of non-linear feedbacks and ES interactions. By including feedbacks between greenhouse gases, stratospheric and tropospheric ozone, aerosols, and clouds, some of which act non-linearly, this work demonstrates the importance of ES interactions when quantifying climate forcing. It also suggests that rapid adjustments need to include chemical as well as physical adjustments to fully account for complex ES interactions.

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Energy Budget Constraints on the Time History of Aerosol Forcing and Climate Sensitivity

Smith

Harris

Palmer

et al. 2021

Preprint

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Aerosol effective radiative forcing (ERF) remains one of the most uncertain components of the present-day climate . Uncertainty in present-day forcing reduces our ability to confidently predict the future climate response to emissions (Forster et al., 2013) and the level of historical greenhouse gas warming masked by the cooling effect of aerosols (Samset et al., 2018). Aerosol forcing is the largest uncertainty governing future committed warming (Matthews & Zickfeld, 2012;Smith et al., 2019) and remaining carbon budgets consistent with Paris Agreement targets (Mengis & Matthews, 2020). In most future socio-economic scenarios, aerosol forcing is projected to become less negative over the 21st century (Gidden et al., 2019;Huppmann et al., 2018;Rogelj et al., 2018), promoting an increase in the rate of warming unless there is a concurrent reduction in greenhouse gas emissions (Shindell & Smith, 2019). The time history of aerosol ERF is a necessary input to many reduced-complexity climate models (Nicholls et al., 2020), which

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Energy budget constraints on historical radiative forcing

Cited by 18 publications

References 49 publications

Assessment of pre-industrial to present-day anthropogenic climate forcing in UKESM1

Assessment of pre-industrial to present-day anthropogenic climate forcing in UKESM1

Assessment of pre-industrial to present-day anthropogenic climate forcing in UKESM1

Energy Budget Constraints on the Time History of Aerosol Forcing and Climate Sensitivity

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