Abstract
Abstract. The impact of black carbon (BC) aerosols on the global radiation balance is not well constrained. Here twelve global aerosol models are used to show that at least 20% of the present uncertainty in modeled BC direct radiative forcing (RF) is due to diversity in the simulated vertical profile of BC mass. Results are from phases 1 and 2 of the global aerosol model intercomparison project (AeroCom). Additionally, a significant fraction of the variability is shown to come from high altitudes, as, globally, more than 40% of the total BC RF is exerted above 5 km. BC emission regions and areas with transported BC are found to have differing characteristics. These insights into the importance of the vertical profile of BC lead us to suggest that observational studies are needed to better characterize the global distribution of BC, including in the upper troposphere.
Highlights
Hydrology and Usonrlbiskesomlaorstraadtmiatoisopnh. eTrihcEisaaewrroatsrhomlsiSn, gyblesafctfkeecmct aorbf oBnC(BhCas) abled to suggestions, both in the scieSnticfiicecnocmemsunity (EditorialNature, 2009; Grieshop et al, 2009; Shindell et al, 2012; Hansen et al, 2000) and among policy makers, for reduction of black carbon (BC) emissions to mitigate global warming
We find a multi-model mean of 0.19 mg m−2, but with a relative standard deviation (RSD) of 32 % and a model spread from 0.09 to 0.37 mg m−2
This is partly due to the strength of the efficiency profile (EP) used, which is higher than for most aerosol model intercomparison project (AeroCom) models, and partly to the fact that the present study includes BC from biomass burning as mentioned above
Summary
Hydrology and Usonrlbiskesomlaorstraadtmiatoisopnh. eTrihcEisaaewrroatsrhomlsiSn, gyblesafctfkeecmct aorbf oBnC(BhCas) abled to suggestions, both in the scieSnticfiicecnocmemsunity (EditorialNature, 2009; Grieshop et al, 2009; Shindell et al, 2012; Hansen et al, 2000) and among policy makers, for reduction of BC emissions to mitigate global warming. ETrihcEisaaewrroatsrhomlsiSn, gyblesafctfkeecmct aorbf oBnC(BhCas) abled to suggestions, both in the scieSnticfiicecnocmemsunity 2009; Grieshop et al, 2009; Shindell et al, 2012; Hansen et al, 2000) and among policy makers, for reduction of BC emissions to mitigate global warming. The uncertainties in the radiatOivecfeoracinngS(RcFie) onfcthee direct aerosol effect of BC are large (Ramanathan and Carmichael, 2008; Schulz et al, 2006; Feichter and Stier, 2012), hampering mitigation studies (Koch et al, 2011a). Among the causes of these model uncertainties are assumptions about the vertical concentration profiles of BC (Zarzycki and Bond, 2010). There are significant discSreopalindcieEs baertwtheen models and observations (Koch et al, 2009)
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