Global and regional radiative forcing from 20 % reductions in BC, OC and SO4 - An HTAP2 multi-model study

Camilla Weum Stjern, Bjørn Hallvard Samset, Gunnar Myhre, Huisheng Bian, Mian Chin, Yanko Davila, Frank Dentener, Louisa Emmons, Johannes Flemming, Amund Søvde Haslerud, Daven Henze, Jan Eiof Jonson, Tom Kucsera, Marianne Tronstad Lund, Michael Schulz, Kengo Sudo, Toshihiko Takemura, Simone Tilmes

    Research output: Contribution to journalArticle

    20 Citations (Scopus)

    Abstract

    In the Hemispheric Transport of Air Pollution Phase 2 (HTAP2) exercise, a range of global atmospheric general circulation and chemical transport models performed coordinated perturbation experiments with 20 % reductions in emissions of anthropogenic aerosols, or aerosol precursors, in a number of source regions. Here, we compare the resulting changes in the atmospheric load and vertically resolved profiles of black carbon (BC), organic aerosols (OA) and sulfate (SO4) from 10 models that include treatment of aerosols. We use a set of temporally, horizontally and vertically resolved profiles of aerosol forcing efficiency (AFE) to estimate the impact of emission changes in six major source regions on global radiative forcing (RF) pertaining to the direct aerosol effect, finding values between. 51.9 and 210.8 mW m-2 Tg-1 for BC, between -2.4 and -17.9 mW m-2 Tg-1 for OA and between -3.6 and -10.3 W m-2 Tg-1 for SO4. In most cases, the local influence dominates, but results show that mitigations in south and east Asia have substantial impacts on the radiative budget in all investigated receptor regions, especially for BC. In Russia and the Middle East, more than 80 % of the forcing for BC and OA is due to extra-regional emission reductions. Similarly, for North America, BC emissions control in east Asia is found to be more important than domestic mitigations, which is consistent with previous findings. Comparing fully resolved RF calculations to RF estimates based on vertically averaged AFE profiles allows us to quantify the importance of vertical resolution to RF estimates. We find that locally in the source regions, a 20 % emission reduction strengthens the radiative forcing associated with SO4 by 25 % when including the vertical dimension, as the AFE for SO4 is strongest near the surface. Conversely, the local RF from BC weakens by 37 % since BC AFE is low close to the ground. The fraction of BC direct effect forcing attributable to intercontinental transport, on the other hand, is enhanced by one-third when accounting for the vertical aspect, because long-range transport primarily leads to aerosol changes at high altitudes, where the BC AFE is strong. While the surface temperature response may vary with the altitude of aerosol change, the analysis in the present study is not extended to estimates of temperature or precipitation changes.

    Original languageEnglish
    Pages (from-to)13579-13599
    Number of pages21
    JournalAtmospheric Chemistry and Physics
    Volume16
    Issue number21
    DOIs
    Publication statusPublished - Nov 1 2016

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    radiative forcing
    black carbon
    atmospheric pollution
    aerosol
    mitigation
    emission control
    long range transport
    carbon emission
    surface temperature

    All Science Journal Classification (ASJC) codes

    • Atmospheric Science

    Cite this

    Stjern, C. W., Samset, B. H., Myhre, G., Bian, H., Chin, M., Davila, Y., ... Tilmes, S. (2016). Global and regional radiative forcing from 20 % reductions in BC, OC and SO4 - An HTAP2 multi-model study. Atmospheric Chemistry and Physics, 16(21), 13579-13599. https://doi.org/10.5194/acp-16-13579-2016

    Global and regional radiative forcing from 20 % reductions in BC, OC and SO4 - An HTAP2 multi-model study. / Stjern, Camilla Weum; Samset, Bjørn Hallvard; Myhre, Gunnar; Bian, Huisheng; Chin, Mian; Davila, Yanko; Dentener, Frank; Emmons, Louisa; Flemming, Johannes; Haslerud, Amund Søvde; Henze, Daven; Jonson, Jan Eiof; Kucsera, Tom; Lund, Marianne Tronstad; Schulz, Michael; Sudo, Kengo; Takemura, Toshihiko; Tilmes, Simone.

    In: Atmospheric Chemistry and Physics, Vol. 16, No. 21, 01.11.2016, p. 13579-13599.

    Research output: Contribution to journalArticle

    Stjern, CW, Samset, BH, Myhre, G, Bian, H, Chin, M, Davila, Y, Dentener, F, Emmons, L, Flemming, J, Haslerud, AS, Henze, D, Jonson, JE, Kucsera, T, Lund, MT, Schulz, M, Sudo, K, Takemura, T & Tilmes, S 2016, 'Global and regional radiative forcing from 20 % reductions in BC, OC and SO4 - An HTAP2 multi-model study', Atmospheric Chemistry and Physics, vol. 16, no. 21, pp. 13579-13599. https://doi.org/10.5194/acp-16-13579-2016
    Stjern, Camilla Weum ; Samset, Bjørn Hallvard ; Myhre, Gunnar ; Bian, Huisheng ; Chin, Mian ; Davila, Yanko ; Dentener, Frank ; Emmons, Louisa ; Flemming, Johannes ; Haslerud, Amund Søvde ; Henze, Daven ; Jonson, Jan Eiof ; Kucsera, Tom ; Lund, Marianne Tronstad ; Schulz, Michael ; Sudo, Kengo ; Takemura, Toshihiko ; Tilmes, Simone. / Global and regional radiative forcing from 20 % reductions in BC, OC and SO4 - An HTAP2 multi-model study. In: Atmospheric Chemistry and Physics. 2016 ; Vol. 16, No. 21. pp. 13579-13599.
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    abstract = "In the Hemispheric Transport of Air Pollution Phase 2 (HTAP2) exercise, a range of global atmospheric general circulation and chemical transport models performed coordinated perturbation experiments with 20 {\%} reductions in emissions of anthropogenic aerosols, or aerosol precursors, in a number of source regions. Here, we compare the resulting changes in the atmospheric load and vertically resolved profiles of black carbon (BC), organic aerosols (OA) and sulfate (SO4) from 10 models that include treatment of aerosols. We use a set of temporally, horizontally and vertically resolved profiles of aerosol forcing efficiency (AFE) to estimate the impact of emission changes in six major source regions on global radiative forcing (RF) pertaining to the direct aerosol effect, finding values between. 51.9 and 210.8 mW m-2 Tg-1 for BC, between -2.4 and -17.9 mW m-2 Tg-1 for OA and between -3.6 and -10.3 W m-2 Tg-1 for SO4. In most cases, the local influence dominates, but results show that mitigations in south and east Asia have substantial impacts on the radiative budget in all investigated receptor regions, especially for BC. In Russia and the Middle East, more than 80 {\%} of the forcing for BC and OA is due to extra-regional emission reductions. Similarly, for North America, BC emissions control in east Asia is found to be more important than domestic mitigations, which is consistent with previous findings. Comparing fully resolved RF calculations to RF estimates based on vertically averaged AFE profiles allows us to quantify the importance of vertical resolution to RF estimates. We find that locally in the source regions, a 20 {\%} emission reduction strengthens the radiative forcing associated with SO4 by 25 {\%} when including the vertical dimension, as the AFE for SO4 is strongest near the surface. Conversely, the local RF from BC weakens by 37 {\%} since BC AFE is low close to the ground. The fraction of BC direct effect forcing attributable to intercontinental transport, on the other hand, is enhanced by one-third when accounting for the vertical aspect, because long-range transport primarily leads to aerosol changes at high altitudes, where the BC AFE is strong. While the surface temperature response may vary with the altitude of aerosol change, the analysis in the present study is not extended to estimates of temperature or precipitation changes.",
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    T1 - Global and regional radiative forcing from 20 % reductions in BC, OC and SO4 - An HTAP2 multi-model study

    AU - Stjern, Camilla Weum

    AU - Samset, Bjørn Hallvard

    AU - Myhre, Gunnar

    AU - Bian, Huisheng

    AU - Chin, Mian

    AU - Davila, Yanko

    AU - Dentener, Frank

    AU - Emmons, Louisa

    AU - Flemming, Johannes

    AU - Haslerud, Amund Søvde

    AU - Henze, Daven

    AU - Jonson, Jan Eiof

    AU - Kucsera, Tom

    AU - Lund, Marianne Tronstad

    AU - Schulz, Michael

    AU - Sudo, Kengo

    AU - Takemura, Toshihiko

    AU - Tilmes, Simone

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    N2 - In the Hemispheric Transport of Air Pollution Phase 2 (HTAP2) exercise, a range of global atmospheric general circulation and chemical transport models performed coordinated perturbation experiments with 20 % reductions in emissions of anthropogenic aerosols, or aerosol precursors, in a number of source regions. Here, we compare the resulting changes in the atmospheric load and vertically resolved profiles of black carbon (BC), organic aerosols (OA) and sulfate (SO4) from 10 models that include treatment of aerosols. We use a set of temporally, horizontally and vertically resolved profiles of aerosol forcing efficiency (AFE) to estimate the impact of emission changes in six major source regions on global radiative forcing (RF) pertaining to the direct aerosol effect, finding values between. 51.9 and 210.8 mW m-2 Tg-1 for BC, between -2.4 and -17.9 mW m-2 Tg-1 for OA and between -3.6 and -10.3 W m-2 Tg-1 for SO4. In most cases, the local influence dominates, but results show that mitigations in south and east Asia have substantial impacts on the radiative budget in all investigated receptor regions, especially for BC. In Russia and the Middle East, more than 80 % of the forcing for BC and OA is due to extra-regional emission reductions. Similarly, for North America, BC emissions control in east Asia is found to be more important than domestic mitigations, which is consistent with previous findings. Comparing fully resolved RF calculations to RF estimates based on vertically averaged AFE profiles allows us to quantify the importance of vertical resolution to RF estimates. We find that locally in the source regions, a 20 % emission reduction strengthens the radiative forcing associated with SO4 by 25 % when including the vertical dimension, as the AFE for SO4 is strongest near the surface. Conversely, the local RF from BC weakens by 37 % since BC AFE is low close to the ground. The fraction of BC direct effect forcing attributable to intercontinental transport, on the other hand, is enhanced by one-third when accounting for the vertical aspect, because long-range transport primarily leads to aerosol changes at high altitudes, where the BC AFE is strong. While the surface temperature response may vary with the altitude of aerosol change, the analysis in the present study is not extended to estimates of temperature or precipitation changes.

    AB - In the Hemispheric Transport of Air Pollution Phase 2 (HTAP2) exercise, a range of global atmospheric general circulation and chemical transport models performed coordinated perturbation experiments with 20 % reductions in emissions of anthropogenic aerosols, or aerosol precursors, in a number of source regions. Here, we compare the resulting changes in the atmospheric load and vertically resolved profiles of black carbon (BC), organic aerosols (OA) and sulfate (SO4) from 10 models that include treatment of aerosols. We use a set of temporally, horizontally and vertically resolved profiles of aerosol forcing efficiency (AFE) to estimate the impact of emission changes in six major source regions on global radiative forcing (RF) pertaining to the direct aerosol effect, finding values between. 51.9 and 210.8 mW m-2 Tg-1 for BC, between -2.4 and -17.9 mW m-2 Tg-1 for OA and between -3.6 and -10.3 W m-2 Tg-1 for SO4. In most cases, the local influence dominates, but results show that mitigations in south and east Asia have substantial impacts on the radiative budget in all investigated receptor regions, especially for BC. In Russia and the Middle East, more than 80 % of the forcing for BC and OA is due to extra-regional emission reductions. Similarly, for North America, BC emissions control in east Asia is found to be more important than domestic mitigations, which is consistent with previous findings. Comparing fully resolved RF calculations to RF estimates based on vertically averaged AFE profiles allows us to quantify the importance of vertical resolution to RF estimates. We find that locally in the source regions, a 20 % emission reduction strengthens the radiative forcing associated with SO4 by 25 % when including the vertical dimension, as the AFE for SO4 is strongest near the surface. Conversely, the local RF from BC weakens by 37 % since BC AFE is low close to the ground. The fraction of BC direct effect forcing attributable to intercontinental transport, on the other hand, is enhanced by one-third when accounting for the vertical aspect, because long-range transport primarily leads to aerosol changes at high altitudes, where the BC AFE is strong. While the surface temperature response may vary with the altitude of aerosol change, the analysis in the present study is not extended to estimates of temperature or precipitation changes.

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