scholarly journals Aerosol radiative effects with MACv2

2019 ◽  
Author(s):  
Stefan Kinne
Keyword(s):  
Anthropogenic Sources ◽  
Transfer Model ◽  
Strong Impact ◽  
Radiative Effects ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Aerosol Forcing ◽  
Aerosol Radiative Effects ◽  
The Impact ◽  
Aerosol Radiative

Abstract. onthly global maps for aerosol properties of the MACv2 climatology are applied in an off-line radiative transfer model to determine aerosol radiative effects. For details beyond global averages in most cases global maps are presented to visualize regional and seasonal details. Aside from the direct radiative (aerosol presence) effect, including those for aerosol components as extracted from MACv2 aerosol optics, also the major aerosol indirect radiative effect is covered. Hereby, the impact of smaller drops in water clouds due to added anthropogenic aerosol was simulated by applying a satellite retrieval based fit from locally associations between aerosol and drop concentrations over oceans. Present-day anthropogenic aerosols of MACv2 – on a global average basis – reduce the radiative net-fluxes at the top of the atmosphere (TOA) by −1.0 W/m2 and at the surface by −2.1 W/m2. Direct cooling contributions are only about half of indirect contributions (−.35 vs −.65) at TOA, but about twice at the surface (−1.45 vs −.65), as solar absorption of the direct effect warms the atmosphere by +1.1 W/m2. Natural aerosols are on average less absorbing (for a relatively larger solar TOA cooling) and larger in size (now contributing with IR greenhouse warming). Thus, average TOA direct forcing efficiencies for total and anthropogenic aerosol happen to be similar: −11 W/m2/AOD at all-sky and −24 W/m2/AOD at clear-sky conditions. The present-day direct impact by all soot (BC) is globally averaged +0.55W/m2 and at least half of it should be attributed to anthropogenic sources. Hereby any accuracy of anthropogenic impacts, not just for soot, suffers from the limited access to a pre-industrial reference. Anthropogenic uncertainty has a particular strong impact on aerosol indirect effects, which dominate the (TOA) forcing. Accounting for uncertainties in the anthropogenic definition, present-day aerosol forcing is estimated to stay within the −0.7 to −1.6 W/m2 range, with a best estimate at −1 W/m2. Calculations with model predicted temporal changes to anthropogenic AOD indicate that qualitatively the anthropogenic aerosol forcing has not changed much over the last decades and is not likely to increase over the next decades, despite strong regional shifts. These regional shifts explain most solar insolation (brightening or dimming) trends that have been observed by ground-based radiation data.

scholarly journals Aerosol radiative effects with MACv2

2019 ◽  
Vol 19 (16) ◽  
pp. 10919-10959 ◽  
Author(s):  
Stefan Kinne
Keyword(s):  
Direct Effect ◽  
Indirect Effects ◽  
Anthropogenic Sources ◽  
Current Evidence ◽  
Direct Effects ◽  
Radiative Effects ◽  
Anthropogenic Aerosol ◽  
Aerosol Radiative Effects ◽  
Sky Conditions ◽  
Aerosol Radiative

Abstract. Monthly global maps for aerosol properties of the Max Planck Aerosol Climatology version 2 (MACv2) are applied in an offline radiative transfer model to determine aerosol radiative effects. This model setup cannot address rapid adjustments by clouds, but current evidence suggests their contribution to be small when compared to the instantaneous radiative forcing. Global maps are presented to detail the regional and seasonal variability associated with (annual) global averages. Radiative effects caused by the aerosol presence (direct effects) and by aerosol modified clouds (indirect effects) are examined. Direct effects are determined for total aerosol, anthropogenic aerosol and extracted individual aerosol components. Indirect effects cover the impact of reduced cloud drop sizes by anthropogenic aerosol. Present-day global annual radiative effects for anthropogenic aerosol yield (1) a climate cooling of −1.0 W m−2 at the top of the atmosphere (TOA); (2) a surface net-flux reduction of −2.1 W m−2; and, by difference; (3) an atmospheric effect of +1.1 W m−2. This atmospheric solar heating is almost entirely a direct effect. On a global basis, indirect effects (−0.65 W m−2) dominate direct effects (−0.35 W m−2) for the present-day climate response at the TOA, whereas the present-day surface radiative budget is more strongly reduced by direct effects (−1.45 W m−2) than by indirect effects (−0.65 W m−2). Natural aerosols are on average less absorbing and larger in size. However, their stronger solar TOA cooling efficiency is offset by a non-negligible infrared (IR) greenhouse warming efficiency. In the sum the global average annual direct forcing efficiencies (per unit AOD) for natural and anthropogenic aerosol are similar: −12 W m−2 per unit AOD for all-sky conditions and −24 W m−2 per unit AOD for clear-sky conditions. The present-day direct TOA impact by all soot (BC) is +0.55 W m−2, when globally and annually averaged. Between +0.25 and +0.45 W m−2 of that can be attributed to anthropogenic sources, depending on assumptions for the preindustrial BC reference state. Similarly, the preindustrial fine-mode reference uncertainty has a strong influence not just on the direct effect but even more on the indirect effect. Present-day aerosol TOA forcing is estimated to stay within the −0.7 to −1.6 W m−2 range (with the best estimate at −1.0 W m−2). Calculations with scaled temporal changes to anthropogenic AOD from global modeling indicate that the global annual aerosol forcing has not changed much over the last decades, despite strong shifts in regional maxima for anthropogenic AOD. These regional shifts explain most solar insolation (brightening or dimming) trends that have been observed by ground-based radiation data.

scholarly journals Estimating the CMIP6 Anthropogenic Aerosol Radiative Effects with the Advantage of Prescribed Aerosol Forcing

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 406
Author(s):  
Xiangjun Shi ◽  
Chunhan Li ◽  
Lijuan Li ◽  
Wentao Zhang ◽  
Jiaojiao Liu
Keyword(s):  
Radiative Forcing ◽  
Radiative Effects ◽  
Anthropogenic Aerosol ◽  
Global Average ◽  
Aerosol Cloud ◽  
Aerosol Forcing ◽  
Simulation Results ◽  
Aerosol Cloud Interactions ◽  
Aerosol Radiative Effects ◽  
Aerosol Radiative

The prescribed anthropogenic aerosol forcing recommended by Coupled Model Intercomparison Project Phase 6 (CMIP6) was implemented in an atmospheric model. With the reduced complexity of anthropogenic aerosol forcing, each component of anthropogenic aerosol effective radiative forcing (ERF) can be estimated by one or more calculation methods, especially for instantaneous radiative forcing (RF) from aerosol–radiation interactions (RFari) and aerosol–cloud interactions (RFaci). Simulation results show that the choice of calculation method might impact the magnitude and reliability of RFari. The RFaci—calculated by double radiation calls—is the definition-based Twomey effect, which previously was impossible to diagnose using the default model with physically based aerosol–cloud interactions. The RFari and RFaci determined from present-day simulations are very robust and can be used as offline simulation results. The robust RFari, RFaci, and corresponding radiative forcing efficiencies (i.e., the impact of environmental properties) are very useful for analyzing anthropogenic aerosol radiative effects. For instance, from 1975 to 2000, both RFari and RFaci showed a clear response to the spatial change of anthropogenic aerosol. The global average RF (RFari + RFaci) has enhanced (more negative) by ~6%, even with a slight decrease in the global average anthropogenic aerosol, and this can be explained by the spatial pattern of radiative forcing efficiency.

scholarly journals Anthropogenic aerosol forcing under the Shared Socioeconomic Pathways

2019 ◽  
Author(s):  
Marianne T. Lund ◽  
Gunnar Myhre ◽  
Bjørn H. Samset
Keyword(s):  
Air Pollution ◽  
Radiative Forcing ◽  
Global Climate ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Air Pollution Control ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Aerosol Radiative Forcing ◽  
Aerosol Forcing

Abstract. Emissions of anthropogenic aerosols are expected to change drastically over the coming decades, with potentially significant climate implications. Using the most recent generation of harmonized emission scenarios, the Shared Socioeconomic Pathways (SSPs) as input to a global chemistry transport and radiative transfer model, we provide estimates of the projected future global and regional burdens and radiative forcing of anthropogenic aerosols under three different levels of air pollution control: strong (SSP1), medium (SSP2) and weak (SSP3). We find that the broader range of future air pollution emission trajectories spanned by the SSPs compared to previous scenarios translates into total aerosol forcing estimates in 2100 relative to 1750 ranging from −0.04 W m−2 in SSP1-1.9 to −0.51 W m−2 in SSP3-7.0. Compared to our 1750–2015 estimate of −0.61 W m−2, this shows that depending on the success of air pollution policies over the coming decades, aerosol radiative forcing may weaken by nearly 95 % or remain close to the pre-industrial to present-day level. In all three scenarios there is a positive forcing in 2100 relative to 2015, from 0.51 W m−2 in SSP1-1.9 to 0.04 W m−2 in SSP3-7.0. Results also demonstrate significant differences across regions and scenarios, especially in South Asia and Africa. While rapid weakening of the negative aerosol forcing following effective air quality policies will unmask more of the greenhouse gas-induced global warming, slow progress on mitigating air pollution will significantly enhance the atmospheric aerosol levels and risk to human health. In either case, the resulting impacts on regional and global climate can be significant.

scholarly journals Large difference in aerosol radiative effects from BVOC-SOA treatment in three ESMs

2020 ◽  
Author(s):  
Moa K. Sporre ◽  
Sara M. Blichner ◽  
Roland Schrödner ◽  
Inger H. H. Karset ◽  
Terje K. Berntsen ◽  
...  
Keyword(s):  
Aerosol Particles ◽  
Particle Formation ◽  
Earth System ◽  
New Particle Formation ◽  
Aerosol Formation ◽  
Radiative Effects ◽  
Sensitivity Experiments ◽  
Aerosol Radiative Effects ◽  
The Impact ◽  
Aerosol Radiative

Abstract. Biogenic volatile organic compounds (BVOCs) emitted from vegetation are oxidized in the atmosphere and can form aerosol particles either by contributing to new particle formation or by condensing onto existing aerosol particles. As the understanding of the importance of BVOCs for aerosol formation has increased over the past 10 years these processes have made their way into Earth System Models (ESMs). In this study, sensitivity experiments are run with three different ESMs, (the Norwegian Earth System Model (NorESM), EC-Earth and ECHAM) to investigate how the direct and indirect aerosol radiative effects are affected by changes in the formation of secondary organic aerosol (SOA) from BVOCs. In the first two sensitivity model experiments, the yields of SOA precursors from oxidation of BVOCs are changed by ± 50 %. For the third sensitivity test, the formed oxidation products do not participate in the formation of new particles, but are only allowed to condense onto existing aerosols. In the last two sensitivity experiments, the emissions of BVOC compounds (isoprene and monoterpenes) are turned off, one at a time. The results show that the impact on the direct radiative effect (DRE) are linked to the changes in the SOA production in the models, where more SOA leads to a stronger DRE and vice versa. The magnitude by which the DRE changes (maximally 0.15 W m−2 globally averaged) in response to the SOA changes however varies between the models, with EC-Earth displaying the largest changes. The results for the cloud radiative effects (CRE) are more complicated than for the DRE. The changes in CRE differ more among the ESMs and for some sensitivity experiments they even have different signs. The most sensitive models are NorESM and EC-Earth, which has CRE changes of up to 0.82 W m−2. The varying responses in the different models are connected to where in the aerosol size distributions the changes in mass and number due to SOA formation occur, in combination with the aerosol number concentration levels in the models. We also find that interactive gas-phase chemistry as well as the new particle formation parameterization have important implications for the DRE and CRE in some of the sensitivity experiments. The results from this study indicate that BVOC-SOA treatment in ESMs can have a substantial impact on the modelled climate but that the sensitivity varies greatly between the models. Since BVOC emissions have changed historically and will continue to change in the future, the spread in model results found in this study introduces uncertainty into ESM estimates of aerosol forcing from land-use change and BVOC feedback strengths.

scholarly journals Aerosol radiative effects with dual view AOD retrievals

2021 ◽  
Author(s):  
Stefan Kinne ◽  
Peter North ◽  
Kevin Pearson ◽  
Thomas Popp
Keyword(s):  
Greenhouse Effect ◽  
Indirect Effects ◽  
Radiative Effects ◽  
Anthropogenic Aerosol ◽  
Regional Trends ◽  
Satellite Sensors ◽  
General Data ◽  
Net Flux ◽  
Aerosol Radiative Effects ◽  
Aerosol Radiative

Abstract. Seasonal maps of dual view retrieved mid-visible AOD and AODf for four selected years (1998, 2008, 2019, 2020) are introduced and assessed in comparisons to MODIS retrievals and general data of an aerosol climatology. Due to different sensor capabilities (ATSR-2, AATSR and SLSTR) there are still unresolved inconsistencies so that decadal regional trends are not as detectable as with MODIS retrievals. SLSTR retrieval, however, agree with MODIS retrievals that 2020 Covid impacts on AOD values (via comparisons to the pre-COVID 2019 reference) are at best minor and secondary to natural anomalies by wildfires and dust. In radiative transfer applications the dual view AOD data for the four years are processed in the MAC climatology environment to determine aerosol associated radiative effects for total aerosol and for anthropogenic aerosol. Even though the calculated radiative effects are affected by retrieval AOD retrieval tendencies, climate relevant TOA net-flux changes are consistent to result with AOD data from other satellite sensors and a general climatology: −0.9 W/m2 for total aerosol with a significant greenhouse effect and −0.8 and −0.2 W/m2 for anthropogenic aerosol with and without indirect effects, respectively. Aside from global averages, seasonal maps highlight the diversity of regional and seasonal radiative effects.

Implication of the reduction in anthropogenic aerosols due to the COVID-19 pandemic and the future recovery scenarios for radiative forcing

2021 ◽  
Author(s):  
Stephanie Fiedler ◽  
Klaus Wyser ◽  
Rogelj Joeri ◽  
Twan van Noije
Keyword(s):  
Radiative Forcing ◽  
Internal Variability ◽  
Climate Response ◽  
Emission Scenarios ◽  
Radiative Effects ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Aerosol Forcing ◽  
Effective Radiative Forcing ◽  
Aerosol Emissions

<p>The COVID-19 pandemic has led to unprecedented reductions in socio-economic activities. Associated decreases in anthropogenic aerosol emissions are not represented in the original CMIP6 emission scenarios. Here we estimate the implications of the pandemic for the aerosol forcing in 2020 and quantify the spread in aerosol forcing associated with the differences in the post-pandemic recovery pathways. To this end, we use new emission scenarios taking the COVID-19 crisis into account and projecting different socio-economic developments until 2050 with fossil-fuel based and green pathways (Forster et al., 2020). We use the new emission data to generate input for the anthropogenic aerosol parameterization MACv2-SP for CMIP6 models. In this presentation, we first show the results for the anthropogenic aerosol optical depth and associated effects on clouds from the new MACv2-SP data for 2020 to 2050 (Fiedler et al., in review). We then use the MACv2-SP data to provide estimates of the effective radiative effects of the anthropogenic aerosols for 2020 and 2050. Our forcing estimates are based on new atmosphere-only simulations with the CMIP6 model EC-Earth3. The model uses MACv2-SP to represent aerosol-radiation and aerosol-cloud interactions including aerosol effects on cloud lifetime. For each anthropogenic aerosol pattern, we run EC-Earth3 simulations for fifty years to substantially reduce the impact of model-internal variability on the forcing estimate. Our results highlight: (1) a change of +0.04 Wm<sup>-2</sup> in the global mean effective radiative forcing of anthropogenic aerosols for 2020 due to the pandemic, which is small compared to the magnitude of internal variability, (2) a spread of -0.38 to -0.68 Wm<sup>-2</sup> for the effective radiative forcing associated with anthropogenic aerosols in 2050 depending on the recovery scenario in MACv2-SP, and (3) a more negative (stronger) anthropogenic aerosol forcing for a strong green than a moderate green development in 2050 due to higher ammonium emissions in a highly decarbonized society (Fiedler et al., in review). The new MACv2-SP data are now used in climate models participating in the model intercomparison project on the climate response to the COVID-19 crisis (Covid-MIP, Jones et al., in review, Lamboll et al., in review).</p><p><strong>References:</strong></p><p>Fiedler, S., Wyser, K., Joeri, R., and van Noije, T.: Radiative effects of reduced aerosol emissions during the COVID-19 pandemic and the future recovery, in review, [preprint] https://doi.org/10.1002/essoar.10504704.1.</p><p>Forster, P.M., Forster, H.I., Evans, M.J. et al.: Current and future global climate impacts resulting from COVID-19. Nat. Clim. Chang. 10, 913–919, 2020, https://doi.org/10.1038/s41558-020-0883-0.</p><p>Jones. C., Hickman, J., Rumbold, S., et al.: The Climate Response to Emissions Reductions due to COVID-19, Geophy. Res. Lett., in review.</p><p>Lamboll, R. D., Jones, C. D., Skeie, R. B., Fiedler, S., Samset, B. H., Gillett, N. P., Rogelj, J., and Forster, P. M.: Modifying emission scenario projections to account for the effects of COVID-19: protocol for Covid-MIP, in review, [preprint] https://doi.org/10.5194/gmd-2020-373.</p>

scholarly journals Aerosol Direct Radiative Effects under Cloud-Free Conditions over Highly-Polluted Areas in Europe and Mediterranean: A Ten-Years Analysis (2007–2016)

2021 ◽  
Vol 13 (15) ◽  
pp. 2933
Author(s):  
Tony C. Landi ◽  
Paolo Bonasoni ◽  
Michele Brunetti ◽  
James R. Campbell ◽  
Jared W. Marquis ◽  
...  
Keyword(s):  
Heating Rate ◽  
Solar Irradiation ◽  
Sahara Desert ◽  
Radiative Effects ◽  
Anthropogenic Aerosols ◽  
Desert Region ◽  
Po Valley ◽  
Atmospheric Column ◽  
Aerosol Radiative Effects ◽  
Aerosol Radiative

This study investigates changes in aerosol radiative effects on two highly urbanized regions across the Euro-Mediterranean basin with respect to a natural desert region as Sahara over a decade through space-based lidar observations. The research is based on the monthly-averaged vertically-resolved aerosol optical depth (AOD) atmospheric profiles along a 1∘×1∘ horizontal grid, obtained from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument measurements aboard the Cloud-Aerosol lidar and Infrared Pathfinder Satellite Observation (CALIPSO). To assess the variability of the anthropogenic aerosols on climate, we compared the aerosol vertical profile observations to a one-dimensional radiative transfer model in two metropolitan climate sensible hot-spots in Europe, namely the Po Valley and Benelux, to investigate the variability of the aerosol radiative effects and heating rate over ten years. The same analysis is carried out as reference on the Sahara desert region, considered subject just to natural local emission. Our findings show the efficacy of emission reduction policies implemented at government level in strongly urbanized regions. The total atmospheric column aerosol load reduction (not observed in Sahara desert region) in Po Valley and Benelux can be associated with: (i) an increase of the energy flux at the surface via direct effects confirmed also by long term surface temperature observations, (ii) a general decrease of the atmospheric column heating rate, and likely (iii) an increase in surface temperatures during a ten-year period. Summarizing, the analysis, based on the decade 2007–2016, clearly show an increase of solar irradiation under cloud-free conditions at the surface of +3.6 % and +16.6% for the Po Valley and Benelux, respectively, and a reduction of −9.0% for the Sahara Desert.

scholarly journals Anthropogenic aerosol forcing under the Shared Socioeconomic Pathways

2019 ◽  
Vol 19 (22) ◽  
pp. 13827-13839 ◽  
Author(s):  
Marianne T. Lund ◽  
Gunnar Myhre ◽  
Bjørn H. Samset
Keyword(s):  
Air Pollution ◽  
Radiative Forcing ◽  
Socioeconomic Development ◽  
Global Climate ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Pollution Levels ◽  
Aerosol Forcing

Abstract. Emissions of anthropogenic aerosols are expected to change drastically over the coming decades, with potentially significant climate implications. Using the most recent generation of harmonized emission scenarios, the Shared Socioeconomic Pathways (SSPs) as input to a global chemistry transport and radiative transfer model, we provide estimates of the projected future global and regional burdens and radiative forcing of anthropogenic aerosols under three contrasting pathways for air pollution levels: SSP1-1.9, SSP2-4.5 and SSP3-7.0. We find that the broader range of future air pollution emission trajectories spanned by the SSPs compared to previous scenarios translates into total aerosol forcing estimates in 2100 relative to 1750 ranging from −0.04 in SSP1-1.9 to −0.51 W m−2 in SSP3-7.0. Compared to our 1750–2015 estimate of −0.55 W m−2, this shows that, depending on the success of air pollution policies and socioeconomic development over the coming decades, aerosol radiative forcing may weaken by nearly 95 % or remain close to the preindustrial to present-day level. In all three scenarios there is a positive forcing in 2100 relative to 2015, from 0.51 in SSP1-1.9 to 0.04 W m−2 in SSP3-7.0. Results also demonstrate significant differences across regions and scenarios, especially in South Asia and Africa. While rapid weakening of the negative aerosol forcing following effective air quality policies will unmask more of the greenhouse-gas-induced global warming, slow progress on mitigating air pollution will significantly enhance the atmospheric aerosol levels and risk to human health in these regions. In either case, the resulting impacts on regional and global climate can be significant.

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