Concentrations and radiative forcing of anthropogenic aerosols from 1750 to 2014 simulated with the Oslo CTM3 and CEDS emission inventory

Abstract

We document the ability of the new-generation Oslo chemistry-transport model, Oslo CTM3, to accurately simulate present-day aerosol distributions. The model is then used with the new Community Emission Data System (CEDS) historical emission inventory to provide updated time series of anthropogenic aerosol concentrations and consequent direct radiative forcing (RFari) from 1750 to 2014.Overall, Oslo CTM3 performs well compared with measurements of surface concentrations and remotely sensed aerosol optical depth. Concentrations are underestimated in Asia, but the higher emissions in CEDS than previous inventories result in improvements compared to observations. The treatment of black carbon (BC) scavenging in Oslo CTM3 gives better agreement with observed vertical BC profiles relative to the predecessor Oslo CTM2. However, Arctic wintertime BC concentrations remain underestimated, and a range of sensitivity tests indicate that better physical understanding of processes associated with atmospheric BC processing is required to simultaneously reproduce both the observed features. Uncertainties in model input data, resolution, and scavenging affect the distribution of all aerosols species, especially at high latitudes and altitudes. However, we find no evidence of consistently better model performance across all observables and regions in the sensitivity tests than in the baseline configuration.Using CEDS, we estimate a net RFari in 2014 relative to 1750 of − 0.17 W m −2 , significantly weaker than the IPCC AR5 2011-1750 estimate. Differences are attributable to several factors, including stronger absorption by organic aerosol, updated parameterization of BC absorption, and reduced sulfate cooling. The trend towards a weaker RFari over recent years is more pronounced than in the IPCC AR5, illustrating the importance of capturing recent regional emission changes.

Anthropogenic aerosol forcing under the Shared Socioeconomic Pathways

“…Here the model is run in a 2.25 • × 2.25 • horizontal resolution, with 60 vertical levels (the uppermost centered at 0.1 hPa). The present-day aerosol distributions simulated by the OsloCTM3 were recently documented and evaluated by Lund et al (2018). We refer to the same paper for detailed descriptions about the aerosol modules and treatment of scavenging and transport in the OsloCTM3.…”

“…All simulations are performed with meteorological data for 2010. Lund et al (2018) investigated the impact of meteorology on the simulated aerosol abundances using data for 2 years with the opposite El Niño-Southern Oscillation (ENSO) index. Differences in global burden of up to 10 % for some aerosol species were found, with occasional larger values in localized regions over the tropical Pacific and Atlantic oceans.…”

“…Each simulation is run for 18 months, discarding the first six as spin-up. Natural emission sources (soil, ocean, biogenic organic compounds from vegetation) are kept at the present-day level and the data sets described in Lund et al (2018). See Sect.…”

Update and evaluation of the ozone dry deposition in Oslo CTM3 v1.0

“…As the new scheme is quantitatively more similar to the multi-model mean (Hardacre et al, 2015) with respect to dry deposition velocities, while the old scheme agrees better in terms of total dry deposition, there is an apparent discrepancy. By means of tropospheric ozone burden (Gaudel et al, 2018) and surface ozone concentrations deduced from the MACC reanalysis (MACC- II Consortium, 2011), Oslo CTM3 with the operational mOSaic scheme shows a pronounced high bias of tropospheric ozone. While the average bias is small or even reversed when using the old scheme, both display elevated ozone in comparison with the MACC reanalysis in continental regions with high average incoming UV radiation (e.g., northern South America, central and southern Africa, the Himalayas).…”

Update and evaluation of the ozone dry deposition in the Oslo CTM3 v1.0

“…The key components of the Oslo CTM3 have been described and evaluated by Søvde et al (2012). A detailed account of the capabilities of the Oslo CTM3 in simulating anthropogenic aerosol forcing in the past and recent past using the Community Emission Data System (CEDS) historical emission inventory (Hoesly et al, 2018) is given by Lund et al (2018). The Oslo CTM3 can also be coupled to the Model 15 of Emissions of Gases and Aerosols from Nature (MEGAN v2.10) (Guenther et al, 2006).…”