Anthropogenic aerosol forcing - insights from multiple estimates from aerosol-climate models with reduced complexity

Stephanie Fiedler, Stefan Kinne, Wan Ting Katty Huang, Petri Räisänen, Declan O'Donnell, Nicolas Bellouin, Philip Stier, Joonas Merikanto, Twan van Noije, Risto Makkonen, Ulrike Lohmann

Research output: Contribution to journalArticleScientificpeer-review

Abstract

This study assesses the change in anthropogenic aerosol forcing from the mid-1970s to the mid-2000s. Both decades had similar global-mean anthropogenic aerosol optical depths but substantially different global distributions. For both years, we quantify (i) the forcing spread due to model-internal variability and (ii) the forcing spread among models. Our assessment is based on new ensembles of atmosphere-only simulations with five state-of-the-art Earth system models. Four of these models will be used in the sixth Coupled Model Intercomparison Project (CMIP6; Eyring et al., 2016). Here, the complexity of the anthropogenic aerosol has been reduced in the participating models. In all our simulations, we prescribe the same patterns of the anthropogenic aerosol optical properties and associated effects on the cloud droplet number concentration. We calculate the instantaneous radiative forcing (RF) and the effective radiative forcing (ERF). Their difference defines the net contribution from rapid adjustments. Our simulations show a model spread in ERF from -0.4 to -0.9 W m(-2). The standard deviation in annual ERF is 0.3 W m(-2), based on 180 individual estimates from each participating model. This result implies that identifying the model spread in ERF due to systematic differences requires averaging over a sufficiently large number of years. Moreover, we find almost identical ERFs for the mid-1970s and mid-2000s for individual models, although there are major model differences in natural aerosols and clouds. The model-ensemble mean ERF is -0.54 W m(-2) for the pre-industrial era to the mid-1970s and -0.59 W m(-2) for the pre-industrial era to the mid-2000s. Our result suggests that comparing ERF changes between two observable periods rather than absolute magnitudes relative to a poorly constrained pre-industrial state might provide a better test for a model's ability to represent transient climate changes.
Original languageEnglish
JournalAtmospheric Chemistry and Physics
Volume19
Issue number10
Pages (from-to)6821-6841
Number of pages21
ISSN1680-7316
DOIs
Publication statusPublished - 22 May 2019
MoE publication typeA1 Journal article-refereed

Fields of Science

  • EARTH SYSTEM MODEL
  • OPTICAL-PROPERTIES
  • TROPOSPHERIC CHEMISTRY
  • RADIATIVE-TRANSFER
  • SIMULATION
  • PARAMETERIZATION
  • SENSITIVITY
  • FUTURE
  • UNCERTAINTIES
  • VARIABILITY
  • 114 Physical sciences

Cite this

Fiedler, S., Kinne, S., Huang, W. T. K., Räisänen, P., O'Donnell, D., Bellouin, N., ... Lohmann, U. (2019). Anthropogenic aerosol forcing - insights from multiple estimates from aerosol-climate models with reduced complexity. Atmospheric Chemistry and Physics, 19(10), 6821-6841. https://doi.org/10.5194/acp-19-6821-2019
Fiedler, Stephanie ; Kinne, Stefan ; Huang, Wan Ting Katty ; Räisänen, Petri ; O'Donnell, Declan ; Bellouin, Nicolas ; Stier, Philip ; Merikanto, Joonas ; van Noije, Twan ; Makkonen, Risto ; Lohmann, Ulrike. / Anthropogenic aerosol forcing - insights from multiple estimates from aerosol-climate models with reduced complexity. In: Atmospheric Chemistry and Physics. 2019 ; Vol. 19, No. 10. pp. 6821-6841.
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title = "Anthropogenic aerosol forcing - insights from multiple estimates from aerosol-climate models with reduced complexity",
abstract = "This study assesses the change in anthropogenic aerosol forcing from the mid-1970s to the mid-2000s. Both decades had similar global-mean anthropogenic aerosol optical depths but substantially different global distributions. For both years, we quantify (i) the forcing spread due to model-internal variability and (ii) the forcing spread among models. Our assessment is based on new ensembles of atmosphere-only simulations with five state-of-the-art Earth system models. Four of these models will be used in the sixth Coupled Model Intercomparison Project (CMIP6; Eyring et al., 2016). Here, the complexity of the anthropogenic aerosol has been reduced in the participating models. In all our simulations, we prescribe the same patterns of the anthropogenic aerosol optical properties and associated effects on the cloud droplet number concentration. We calculate the instantaneous radiative forcing (RF) and the effective radiative forcing (ERF). Their difference defines the net contribution from rapid adjustments. Our simulations show a model spread in ERF from -0.4 to -0.9 W m(-2). The standard deviation in annual ERF is 0.3 W m(-2), based on 180 individual estimates from each participating model. This result implies that identifying the model spread in ERF due to systematic differences requires averaging over a sufficiently large number of years. Moreover, we find almost identical ERFs for the mid-1970s and mid-2000s for individual models, although there are major model differences in natural aerosols and clouds. The model-ensemble mean ERF is -0.54 W m(-2) for the pre-industrial era to the mid-1970s and -0.59 W m(-2) for the pre-industrial era to the mid-2000s. Our result suggests that comparing ERF changes between two observable periods rather than absolute magnitudes relative to a poorly constrained pre-industrial state might provide a better test for a model's ability to represent transient climate changes.",
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author = "Stephanie Fiedler and Stefan Kinne and Huang, {Wan Ting Katty} and Petri R{\"a}is{\"a}nen and Declan O'Donnell and Nicolas Bellouin and Philip Stier and Joonas Merikanto and {van Noije}, Twan and Risto Makkonen and Ulrike Lohmann",
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Fiedler, S, Kinne, S, Huang, WTK, Räisänen, P, O'Donnell, D, Bellouin, N, Stier, P, Merikanto, J, van Noije, T, Makkonen, R & Lohmann, U 2019, 'Anthropogenic aerosol forcing - insights from multiple estimates from aerosol-climate models with reduced complexity', Atmospheric Chemistry and Physics, vol. 19, no. 10, pp. 6821-6841. https://doi.org/10.5194/acp-19-6821-2019

Anthropogenic aerosol forcing - insights from multiple estimates from aerosol-climate models with reduced complexity. / Fiedler, Stephanie; Kinne, Stefan; Huang, Wan Ting Katty; Räisänen, Petri; O'Donnell, Declan; Bellouin, Nicolas; Stier, Philip; Merikanto, Joonas; van Noije, Twan; Makkonen, Risto; Lohmann, Ulrike.

In: Atmospheric Chemistry and Physics, Vol. 19, No. 10, 22.05.2019, p. 6821-6841.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Anthropogenic aerosol forcing - insights from multiple estimates from aerosol-climate models with reduced complexity

AU - Fiedler, Stephanie

AU - Kinne, Stefan

AU - Huang, Wan Ting Katty

AU - Räisänen, Petri

AU - O'Donnell, Declan

AU - Bellouin, Nicolas

AU - Stier, Philip

AU - Merikanto, Joonas

AU - van Noije, Twan

AU - Makkonen, Risto

AU - Lohmann, Ulrike

PY - 2019/5/22

Y1 - 2019/5/22

N2 - This study assesses the change in anthropogenic aerosol forcing from the mid-1970s to the mid-2000s. Both decades had similar global-mean anthropogenic aerosol optical depths but substantially different global distributions. For both years, we quantify (i) the forcing spread due to model-internal variability and (ii) the forcing spread among models. Our assessment is based on new ensembles of atmosphere-only simulations with five state-of-the-art Earth system models. Four of these models will be used in the sixth Coupled Model Intercomparison Project (CMIP6; Eyring et al., 2016). Here, the complexity of the anthropogenic aerosol has been reduced in the participating models. In all our simulations, we prescribe the same patterns of the anthropogenic aerosol optical properties and associated effects on the cloud droplet number concentration. We calculate the instantaneous radiative forcing (RF) and the effective radiative forcing (ERF). Their difference defines the net contribution from rapid adjustments. Our simulations show a model spread in ERF from -0.4 to -0.9 W m(-2). The standard deviation in annual ERF is 0.3 W m(-2), based on 180 individual estimates from each participating model. This result implies that identifying the model spread in ERF due to systematic differences requires averaging over a sufficiently large number of years. Moreover, we find almost identical ERFs for the mid-1970s and mid-2000s for individual models, although there are major model differences in natural aerosols and clouds. The model-ensemble mean ERF is -0.54 W m(-2) for the pre-industrial era to the mid-1970s and -0.59 W m(-2) for the pre-industrial era to the mid-2000s. Our result suggests that comparing ERF changes between two observable periods rather than absolute magnitudes relative to a poorly constrained pre-industrial state might provide a better test for a model's ability to represent transient climate changes.

AB - This study assesses the change in anthropogenic aerosol forcing from the mid-1970s to the mid-2000s. Both decades had similar global-mean anthropogenic aerosol optical depths but substantially different global distributions. For both years, we quantify (i) the forcing spread due to model-internal variability and (ii) the forcing spread among models. Our assessment is based on new ensembles of atmosphere-only simulations with five state-of-the-art Earth system models. Four of these models will be used in the sixth Coupled Model Intercomparison Project (CMIP6; Eyring et al., 2016). Here, the complexity of the anthropogenic aerosol has been reduced in the participating models. In all our simulations, we prescribe the same patterns of the anthropogenic aerosol optical properties and associated effects on the cloud droplet number concentration. We calculate the instantaneous radiative forcing (RF) and the effective radiative forcing (ERF). Their difference defines the net contribution from rapid adjustments. Our simulations show a model spread in ERF from -0.4 to -0.9 W m(-2). The standard deviation in annual ERF is 0.3 W m(-2), based on 180 individual estimates from each participating model. This result implies that identifying the model spread in ERF due to systematic differences requires averaging over a sufficiently large number of years. Moreover, we find almost identical ERFs for the mid-1970s and mid-2000s for individual models, although there are major model differences in natural aerosols and clouds. The model-ensemble mean ERF is -0.54 W m(-2) for the pre-industrial era to the mid-1970s and -0.59 W m(-2) for the pre-industrial era to the mid-2000s. Our result suggests that comparing ERF changes between two observable periods rather than absolute magnitudes relative to a poorly constrained pre-industrial state might provide a better test for a model's ability to represent transient climate changes.

KW - EARTH SYSTEM MODEL

KW - OPTICAL-PROPERTIES

KW - TROPOSPHERIC CHEMISTRY

KW - RADIATIVE-TRANSFER

KW - SIMULATION

KW - PARAMETERIZATION

KW - SENSITIVITY

KW - FUTURE

KW - UNCERTAINTIES

KW - VARIABILITY

KW - 114 Physical sciences

U2 - 10.5194/acp-19-6821-2019

DO - 10.5194/acp-19-6821-2019

M3 - Article

VL - 19

SP - 6821

EP - 6841

JO - Atmospheric Chemistry and Physics

JF - Atmospheric Chemistry and Physics

SN - 1680-7316

IS - 10

ER -