scholarly journals Sensitivity of black carbon concentrations and climate impact to aging and scavenging in OsloCTM2–M7

2017 ◽  
Vol 17 (9) ◽  
pp. 6003-6022 ◽  
Author(s):  
Marianne T. Lund ◽  
Terje K. Berntsen ◽  
Bjørn H. Samset
Keyword(s):  
Nitric Acid ◽  
Surface Temperature ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Climate Models ◽  
Transport Model ◽  
Climate Impact ◽  
Climate Impacts ◽  
The Arctic ◽  
Effective Parameters

Abstract. Accurate representation of black carbon (BC) concentrations in climate models is a key prerequisite for understanding its net climate impact. BC aging and scavenging are treated very differently in current models. Here, we examine the sensitivity of three-dimensional (3-D), temporally resolved BC concentrations to perturbations to individual model processes in the chemistry transport model OsloCTM2–M7. The main goals are to identify processes related to aerosol aging and scavenging where additional observational constraints may most effectively improve model performance, in particular for BC vertical profiles, and to give an indication of how model uncertainties in the BC life cycle propagate into uncertainties in climate impacts. Coupling OsloCTM2 with the microphysical aerosol module M7 allows us to investigate aging processes in more detail than possible with a simpler bulk parameterization. Here we include, for the first time in this model, a treatment of condensation of nitric acid on BC. Using kernels, we also estimate the range of radiative forcing and global surface temperature responses that may result from perturbations to key tunable parameters in the model. We find that BC concentrations in OsloCTM2–M7 are particularly sensitive to convective scavenging and the inclusion of condensation by nitric acid. The largest changes are found at higher altitudes around the Equator and at low altitudes over the Arctic. Convective scavenging of hydrophobic BC, and the amount of sulfate required for BC aging, are found to be key parameters, potentially reducing bias against HIAPER Pole-to-Pole Observations (HIPPO) flight-based measurements by 60 to 90  %. Even for extensive tuning, however, the total impact on global-mean surface temperature is estimated to less than 0.04 K. Similar results are found when nitric acid is allowed to condense on the BC aerosols. We conclude, in line with previous studies, that a shorter atmospheric BC lifetime broadly improves the comparison with measurements over the Pacific. However, we also find that the model–measurement discrepancies can not be uniquely attributed to uncertainties in a single process or parameter. Model development therefore needs to be focused on improvements to individual processes, supported by a broad range of observational and experimental data, rather than tuning of individual, effective parameters such as the global BC lifetime.

scholarly journals Enhancement of snow albedo reduction and radiative forcing due to coated black carbon in snow

2021 ◽  
Vol 15 (5) ◽  
pp. 2255-2272
Author(s):  
Wei Pu ◽  
Tenglong Shi ◽  
Jiecan Cui ◽  
Yang Chen ◽  
Yue Zhou ◽  
...  
Keyword(s):  
Black Carbon ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Climate Models ◽  
Northern China ◽  
Climate Impact ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Core Shell ◽  
Snow Albedo

Abstract. When black carbon (BC) is mixed internally with other atmospheric particles, the BC light absorption effect is enhanced. This study explicitly resolved the optical properties of coated BC in snow based on the core / shell Mie theory and the Snow, Ice, and Aerosol Radiative (SNICAR) model. Our results indicated that the BC coating effect enhances the reduction in snow albedo by a factor ranging from 1.1–1.8 for a nonabsorbing shell and 1.1–1.3 for an absorbing shell, depending on the BC concentration, snow grain radius, and core / shell ratio. We developed parameterizations of the BC coating effect for application to climate models, which provides a convenient way to accurately estimate the climate impact of BC in snow. Finally, based on a comprehensive set of in situ measurements across the Northern Hemisphere, we determined that the contribution of the BC coating effect to snow light absorption exceeds that of dust over northern China. Notably, high enhancements of snow albedo reduction due to the BC coating effect were found in the Arctic and Tibetan Plateau, suggesting a greater contribution of BC to the retreat of Arctic sea ice and Tibetan glaciers.

scholarly journals Coupled Chemistry-Climate Effects from 2050 Projected Aviation Emissions

2017 ◽  
Author(s):  
Andrew Gettelman ◽  
Chih-Chieh Chen ◽  
Mark Z. Jacobson ◽  
Mary A. Cameron ◽  
Donald J. Wuebbles ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Climate Impact ◽  
Particulate Emissions ◽  
Temperature Changes ◽  
Climate Effects ◽  
Aviation Emissions

Abstract. Analyses of the climate effects of 2050 aviation emissions have been conducted with two coupled Chemistry Climate Models (CCMs) including experiments with coupled ocean models. The baseline 2050 aviation emissions scenario projects emissions ~ 5 times those in 2006. Simulations suggest a corresponding growth in the climate impact of aviation by 2050. Positive radiative forcing from contrails reaches +80 mWm−2. Enhanced upper tropospheric and lower stratospheric ozone (O3) due to aviation nitrogen oxide (NOx) emissions causes a radiative forcing of +60 mWm−2. Changes in methane (CH4) lifetime induced by aviation are estimated to cause −25 mWm−2 of radiative forcing in 2050. Simulations indicate that moderate changes in water vapor emissions from changes in combustion efficiency will not have significant forcing. Non-linear effects due to particles (black carbon and sulfur) included in these calculations suggest an important role for black carbon (BC) in increasing contrail cirrus ice crystal number, leading to net warming. Sulfur emissions brighten clouds and provide a net cooling, but this is dependent on uncertain background sulfur levels. Thus alternative aviation fuels with reduced sulfur and BC may alter the future climate impact of aviation, but the sign is dependent on specific processes represented and the background state. Regional perturbations due to contrail and particulate emissions may result in statistically significant regional surface temperature changes in coupled model simulations in areas near or adjacent to flight corridors, but significant signals only emerge after 20–50 years of simulation. Many regions with high regional aviation forcing do not experience net surface temperature changes because of advective rather than radiative driving of temperatures. Surface temperature signals are not significant globally even in long coupled simulations. Short-lived non-uniform aviation forcing will thus affect climate differently than uniform forcing in the coupled climate system.

scholarly journals Enhancement of snow albedo reduction and radiative forcing due to coated black carbon in snow

2020 ◽  
Author(s):  
Wei Pu ◽  
Tenglong Shi ◽  
Jiecan Cui ◽  
Yang Chen ◽  
Yue Zhou ◽  
...  
Keyword(s):  
Black Carbon ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Climate Models ◽  
Northern China ◽  
Climate Impact ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Core Shell ◽  
Snow Albedo

Abstract. When black carbon (BC) is internally mixed with other atmospheric particles, BC light absorption is effectively enhanced. This study is the first to explicitly resolve the optical properties of coated BC in snow, based on core/shell Mie theory and a snow, ice, and aerosol radiative model (SNICAR). Our results indicate that a "BC coating effect" enhances the reduction of snow albedo by a factor of 1.1–1.8 for a non-absorbing shell and 1.1–1.3 for an absorbing shell, depending on BC concentration, snow grain radius, and core/shell ratio. We develop parameterizations of the BC coating effect for application to climate models, which provides a convenient way to accurately estimate the climate impact of BC in snow. Finally, based on a comprehensive set of in situ measurements across the Northern Hemisphere, we find that the contribution of the BC coating effect to snow light absorption has exceeded that of dust over northern China. Notably, the high enhancements of snow albedo reductions by BC coating effect were found in the Arctic and Tibetan Plateau, suggesting a greater contribution of BC to the retreat of Arctic sea ice and Tibetan glaciers.

scholarly journals Sensitivity of black carbon concentrations and climate impact to aging and scavenging

2016 ◽  
Author(s):  
Marianne T. Lund ◽  
Terje K. Berntsen ◽  
Bjørn H. Samset
Keyword(s):  
Nitric Acid ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Mitigation Strategies ◽  
The Arctic ◽  
Climate Mitigation ◽  
Vertical Profiles ◽  
The Impact ◽  
Model Measurement ◽  
Global Mean

Abstract. Despite recent improvements, significant uncertainties in global modeling of black carbon (BC) aerosols persist, posing important challenges for the design and evaluation of effective climate mitigation strategies targeted at BC emission reductions. Here we investigate the sensitivity of BC concentrations in the chemistry-transport model OsloCTM2 with the microphysical aerosol parameterization M7 (OsloCTM2-M7) to parameters controlling aerosol aging and scavenging. We focus on Arctic surface concentrations and remote region BC vertical profiles, and introduce a novel treatment of condensation of nitric acid on BC. The OsloCTM2-M7 underestimates annual averaged BC surface concentrations, with a mean normalized bias of −0.55. The seasonal cycle and magnitude of Arctic BC surface concentrations is improved compared to previous OsloCTM2 studies, but model-measurement discrepancies during spring remain. High-altitude BC over the Pacific is overestimated compared with measurements from the HIPPO campaigns. We find that a shorter global BC lifetime improves the agreement with HIPPO, in line with other recent studies. Several processes can achieve this, including allowing for convective scavenging of hydrophobic BC and reducing the amount of soluble material required for aging. Simultaneously, the concentrations in the Arctic are reduced, resulting in poorer agreement with measurements in part of the region. A first step towards inclusion of aging by nitrate in OsloCTM2-M7 is made by allowing for condensation of nitric acid on BC. This results in a faster aging and reduced lifetime, and in turn to a better agreement with the HIPPO measurements. On the other hand, model-measurement discrepancies in the Arctic are exacerbated. Work to further improve this parameterization is needed. The impact on global mean radiative forcing (RF) and surface temperature response (TS) in our experiments is estimated. Compared to the baseline, decreases in global mean direct RF on the order of 10–30 % of the total pre-industrial to present BC direct RF is estimated for the experiments that result in the largest changes in BC concentrations. We show that globally tuning parameters related to BC aging and scavenging can improve the representation of BC vertical profiles in the OsloCTM2-M7 compared with observations. Our results also show that such improvements can result from changes in several processes and often depend on assumptions about uncertain parameters such as the BC ice nucleating efficiency and the change in hygroscopicity with aging. It is also important to be aware of potential tradeoffs in model performance between different regions. Other important sources of uncertainty, particularly for Arctic BC, such as model resolution has not been investigated here. Our results underline the importance of more observations and experimental data to improve process understanding and thus further constrain models.

scholarly journals The Climate Impact of COVID19 Induced Contrail Changes

2021 ◽  
Author(s):  
Andrew Gettelman ◽  
Chieh-Chieh Chen ◽  
Charles G. Bardeen
Keyword(s):  
Surface Temperature ◽  
Land Surface ◽  
Radiative Forcing ◽  
Climate Impact ◽  
Climate Impacts ◽  
Infrared Heating ◽  
Boreal Summer ◽  
Surface Temperature Change ◽  
Effective Radiative Forcing ◽  
Standard Deviations

Abstract. The COVID19 pandemic caused significant economic disruption in 2020 and severely impacted air traffic. We use a state of the art Earth System Model and ensembles of tightly constrained simulations to evaluate the effect of the reductions in aviation traffic on contrail radiative forcing and climate in 2020. In the absence of any COVID19 pandemic caused reductions, the model simulates a contrail Effective Radiative Forcing (ERF) 62 ± 59 m Wm−2 (2 standard deviations). The contrail ERF has complex spatial and seasonal patterns that combine the offsetting effect of shortwave (solar) cooling and longwave (infrared) heating from contrails and contrail cirrus. Cooling is larger in June–August due to the preponderance of aviation in the N. Hemisphere, while warming occurs throughout the year. The spatial and seasonal forcing variations also map onto surface temperature variations. The net land surface temperature change due to contrails in a normal year is estimated at 0.13 ± 0.04 K (2 standard deviations) with some regions warming as much as 0.7 K. The effect of COVID19 reductions in flight traffic decreased contrails. The unique timing of such reductions, which were maximum in N. Hemisphere spring and summer when the largest contrail cooling occurs, means that cooling due to fewer contrails in boreal spring and fall was offset by warming due to fewer contrails in boreal summer to give no significant annual averaged ERF from contrail changes in 2020. Despite no net significant global ERF, because of the spatial and seasonal timing of contrail ERF, some land regions that would have cooled slightly (minimum −0.2 K) but significantly from contrail changes in 2020. The implications for future climate impacts of contrails are discussed.

scholarly journals Present-day radiative effect from radiation-absorbing aerosols in snow

2020 ◽  
Author(s):  
Paolo Tuccella ◽  
Giovanni Pitari ◽  
Valentina Colaiuda ◽  
Gabriele Curci
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
Transport Model ◽  
Mineral Soil ◽  
The Arctic ◽  
Carbon Equivalent ◽  
Soil Dust ◽  
Climatic Impact ◽  
Regional Variability ◽  
Absorbing Aerosols

Abstract. Black carbon (BC), brown carbon (BrC) and soil dust are the most radiation absorbing aerosols (RAA). When RAA are deposited on the snowpack, they lower the snow albedo, increasing the absorption of the solar radiation. The climatic impact associated to snow darkening induced by RAA is highly uncertain. In this work, a 5-years simulation with GEOS-Chem global chemistry and transport model was performed, in order to calculate the present-day radiative forcing (RF) of RAA in snow. RF was estimated taking simultaneously into account the presence of BC, BrC, and mineral soil dust in snow. Modelled BC and black carbon equivalent (BCE) mixing ratios in snow and the fraction of light absorption due to non-BC compounds (fnon-BC) were compared with worldwide observations. We showed as BC, BCE and fnon-BC, obtained from deposition and precipitation fluxes, reproduce the regional variability and order of magnitude of the observations. Global mean all sky total RAA, BC, BrC and dust snow RF are 0.068, 0.033, 0.0066, and 0.012 W/m2, respectively. At global scale, non-BC compounds account for 40 % of RAA snow RF, while anthropogenic RAAs contribute to the forcing for 56 %. With regard to non-BC compounds, the largest impact of BrC has been found during summer in the Arctic (+0.13 W/m2). In the middle latitudes of Asia, dust forcing in spring accounts for the 50 % (+0.24 W/m2) of the total RAAs RF. Uncertainties in absorbing optical properties, RAA mixing ratio in snow, snow grain dimension, and snow cover fraction result in an overall uncertainty of −50% / +61 %, −57 % / +183 %, −63 % / +112 %, and −49 % / +77 % in BC, BrC, dust and total RAAs snow RF, respectively.

scholarly journals Sources of carbonaceous aerosols and deposited black carbon in the Arctic in winter-spring: implications for radiative forcing

2011 ◽  
Vol 11 (23) ◽  
pp. 12453-12473 ◽  
Author(s):  
Q. Wang ◽  
D. J. Jacob ◽  
J. A. Fisher ◽  
J. Mao ◽  
E. M. Leibensperger ◽  
...  
Keyword(s):  
Black Carbon ◽  
North American ◽  
Radiative Forcing ◽  
Transport Model ◽  
Anthropogenic Sources ◽  
The Arctic ◽  
Anthropogenic Source ◽  
Carbonaceous Aerosols ◽  
The North ◽  
North American Arctic

Abstract. We use a global chemical transport model (GEOS-Chem CTM) to interpret observations of black carbon (BC) and organic aerosol (OA) from the NASA ARCTAS aircraft campaign over the North American Arctic in April 2008, as well as longer-term records in surface air and in snow (2007–2009). BC emission inventories for North America, Europe, and Asia in the model are tested by comparison with surface air observations over these source regions. Russian open fires were the dominant source of OA in the Arctic troposphere during ARCTAS but we find that BC was of prevailingly anthropogenic (fossil fuel and biofuel) origin, particularly in surface air. This source attribution is confirmed by correlation of BC and OA with acetonitrile and sulfate in the model and in the observations. Asian emissions are the main anthropogenic source of BC in the free troposphere but European, Russian and North American sources are also important in surface air. Russian anthropogenic emissions appear to dominate the source of BC in Arctic surface air in winter. Model simulations for 2007–2009 (to account for interannual variability of fires) show much higher BC snow content in the Eurasian than the North American Arctic, consistent with the limited observations. We find that anthropogenic sources contribute 90% of BC deposited to Arctic snow in January-March and 60% in April–May 2007–2009. The mean decrease in Arctic snow albedo from BC deposition is estimated to be 0.6% in spring, resulting in a regional surface radiative forcing consistent with previous estimates.

scholarly journals Effects of mixing state on optical and radiative properties of black carbon in the European Arctic

2018 ◽  
Author(s):  
Marco Zanatta ◽  
Paolo Laj ◽  
Martin Gysel ◽  
Urs Baltensperger ◽  
Stergios Vratolis ◽  
...  
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
Particle Diameter ◽  
Arctic Region ◽  
Climate Impacts ◽  
Radiative Properties ◽  
The Arctic ◽  
Absorption Enhancement ◽  
Equivalent Diameter ◽  
Mixing State

Abstract. Atmospheric aging promotes internal mixing of black carbon (BC) leading to an enhancement of light absorption and radiative forcing. The relationship between BC mixing state and consequent absorption enhancement was never estimated for BC found in the Arctic region. In the present work, we aim to quantify the absorption enhancement and its impact on radiative forcing as a function of microphysical properties and mixing state of BC observed in-situ at the Zeppelin Arctic station (78° N) in the spring of 2012 during the CLIMSLIP (Climate impacts of short-lived pollutants in the Arctic) project. Single particle soot photometer (SP2) measurements showed a mean mass concentration of refractory black carbon (rBC) of 39 ng m−3, while the rBC mass size distribution was of log-normal shape peaking at an rBC mass equivalent diameter (DrBC) of around 240 nm. On average, the number fraction of particles containing a BC core with DrBC > 80 nm was less than 5 % in the size range (overall optical particle diameter) from 150–500 nm. The BC cores were internally mixed with other particulate matter. The median coating thickness of BC cores with 220 nm 

scholarly journals Variability, timescales, and non-linearity in climate responses to black carbon emissions

2018 ◽  
Author(s):  
Yang Yang ◽  
Steven J. Smith ◽  
Hailong Wang ◽  
Catrin M. Mills ◽  
Philip J. Rasch
Keyword(s):  
Surface Temperature ◽  
Black Carbon ◽  
Climate Models ◽  
The Arctic ◽  
Transient Temperature ◽  
Quasi Equilibrium ◽  
Earth System ◽  
Large Variability ◽  
Temperature Responses ◽  
Climate Responses

Abstract. Black carbon (BC) particles exert a potentially large warming influence on the Earth system. Reductions in BC emissions have attracted attention as a possible means to moderate near-term temperature changes. For the first time, we evaluate regional climate responses, non-linearity, and short-term transient responses to BC emission perturbations in the Arctic, mid-latitudes, and globally based on a comprehensive set of emission-driven experiments using the Community Earth System Model (CESM). Surface temperature responses to BC emissions are complex, with surface warming over land from mid-latitude BC perturbations partially offset by ocean cooling. Climate responses do not scale linearity with emissions. While stronger BC emission perturbations have a higher burden efficiency, their temperature sensitivity is lower. BC impacts temperature much faster than greenhouse gas forcing, with transient temperature responses in the Arctic and mid-latitudes approaching a quasi-equilibrium state with a timescale of 2–3 years. We find large variability in BC-induced climate changes due to background model noise. As a result, perturbing present-day BC emission levels results in no discernible net global-average surface temperature signal. In order to better understand the climatic impacts of BC emissions, both the drivers of non-linear responses and response variability need to be assessed across climate models.

scholarly journals Climate impact of Finnish air pollutants and greenhouse gases using multiple emission metrics

2019 ◽  
Vol 19 (11) ◽  
pp. 7743-7757 ◽  
Author(s):  
Kaarle Juhana Kupiainen ◽  
Borgar Aamaas ◽  
Mikko Savolahti ◽  
Niko Karvosenoja ◽  
Ville-Veikko Paunu
Keyword(s):  
Temperature Change ◽  
Air Pollutants ◽  
Climate Models ◽  
Climate Impact ◽  
Climate Impacts ◽  
Mitigation Measures ◽  
The Arctic ◽  
Climate Effect ◽  
Time Horizons ◽  
Arctic Temperature

Abstract. We present a case study where emission metric values from different studies are applied to estimate global and Arctic temperature impacts of emissions from a northern European country. This study assesses the climate impact of Finnish air pollutants and greenhouse gas emissions from 2000 to 2010, as well as future emissions until 2030. We consider both emission pulses and emission scenarios. The pollutants included are SO2, NOx, NH3, non-methane volatile organic compound (NMVOC), black carbon (BC), organic carbon (OC), CO, CO2, CH4 and N2O, and our study is the first one for Finland to include all of them in one coherent dataset. These pollutants have different atmospheric lifetimes and influence the climate differently; hence, we look at different climate metrics and time horizons. The study uses the global warming potential (GWP and GWP*), the global temperature change potential (GTP) and the regional temperature change potential (RTP) with different timescales for estimating the climate impacts by species and sectors globally and in the Arctic. We compare the climate impacts of emissions occurring in winter and summer. This assessment is an example of how the climate impact of emissions from small countries and sources can be estimated, as it is challenging to use climate models to study the climate effect of national policies in a multi-pollutant situation. Our methods are applicable to other countries and regions and present a practical tool to analyze the climate impacts in multiple dimensions, such as assessing different sectors and mitigation measures. While our study focuses on short-lived climate forcers, we found that the CO2 emissions have the most significant climate impact, and the significance increases over longer time horizons. In the short term, emissions of especially CH4 and BC played an important role as well. The warming impact of BC emissions is enhanced during winter. Many metric choices are available, but our findings hold for most choices.

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