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| Titel |
Radiative forcing in the ACCMIP historical and future climate simulations |
| VerfasserIn |
D. T. Shindell  , J.-F. Lamarque, M. Schulz, M. Flanner, C. Jiao, M. Chin, P. J. Young, Y. H. Lee, L. Rotstayn, N. Mahowald, G. Milly, G. Faluvegi, Y. Balkanski, W. J. Collins, A. J. Conley, S. Dalsoren, R. Easter, S. Ghan, L. Horowitz, X. Liu, G. Myhre, T. Nagashima, V. Naik, S. T. Rumbold, R. Skeie, K. Sudo, S. Szopa, T. Takemura, A. Voulgarakis, J.-H. Yoon, F. Lo |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 6 ; Nr. 13, no. 6 (2013-03-15), S.2939-2974 |
| Datensatznummer |
250018512
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| Publikation (Nr.) |
 copernicus.org/acp-13-2939-2013.pdf |
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| Zusammenfassung |
The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)
examined the short-lived drivers of climate change in current climate
models. Here we evaluate the 10 ACCMIP models that included aerosols, 8 of
which also participated in the Coupled Model Intercomparison Project phase 5
(CMIP5).
The models reproduce present-day total aerosol optical depth (AOD)
relatively well, though many are biased low. Contributions from individual
aerosol components are quite different, however, and most models
underestimate east Asian AOD. The models capture most 1980–2000 AOD trends
well, but underpredict increases over the Yellow/Eastern Sea. They strongly
underestimate absorbing AOD in many regions.
We examine both the direct radiative forcing (RF) and the forcing including
rapid adjustments (effective radiative forcing; ERF, including direct and
indirect effects). The models' all-sky 1850 to 2000 global mean annual
average total aerosol RF is (mean; range) −0.26 W m−2; −0.06 to −0.49 W m−2.
Screening based on model skill in capturing observed AOD yields a
best estimate of −0.42 W m−2; −0.33 to −0.50 W m−2, including
adjustment for missing aerosol components in some models. Many ACCMIP and
CMIP5 models appear to produce substantially smaller aerosol RF than this
best estimate. Climate feedbacks contribute substantially (35 to −58%) to
modeled historical aerosol RF. The 1850 to 2000 aerosol ERF is −1.17 W m−2;
−0.71 to −1.44 W m−2. Thus adjustments, including clouds,
typically cause greater forcing than direct RF. Despite this, the
multi-model spread relative to the mean is typically the same for ERF as it
is for RF, or even smaller, over areas with substantial forcing. The largest
1850 to 2000 negative aerosol RF and ERF values are over and near Europe,
south and east Asia and North America. ERF, however, is positive over the
Sahara, the Karakoram, high Southern latitudes and especially the Arctic.
Global aerosol RF peaks in most models around 1980, declining thereafter
with only weak sensitivity to the Representative Concentration Pathway
(RCP). One model, however, projects approximately stable RF levels, while two
show increasingly negative RF due to nitrate (not included in most models).
Aerosol ERF, in contrast, becomes more negative during 1980 to 2000. During
this period, increased Asian emissions appear to have a larger impact on
aerosol ERF than European and North American decreases due to their being
upwind of the large, relatively pristine Pacific Ocean. There is no clear
relationship between historical aerosol ERF and climate sensitivity in the
CMIP5 subset of ACCMIP models. In the ACCMIP/CMIP5 models, historical
aerosol ERF of about −0.8 to −1.5 W m−2 is most consistent with
observed historical warming. Aerosol ERF masks a large portion of greenhouse
forcing during the late 20th and early 21st century at the global
scale. Regionally, aerosol ERF is so large that net forcing is negative over
most industrialized and biomass burning regions through 1980, but remains
strongly negative only over east and southeast Asia by 2000. Net forcing is
strongly positive by 1980 over most deserts, the Arctic, Australia, and most
tropical oceans. Both the magnitude of and area covered by positive forcing
expand steadily thereafter. |
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