scholarly journals Rapid Adjustments Cause Weak Surface Temperature Response to Increased Black Carbon Concentrations

2017 ◽  
Vol 122 (21) ◽  
pp. 11,462-11,481 ◽  
Author(s):  
Camilla Weum Stjern ◽  
Bjørn Hallvard Samset ◽  
Gunnar Myhre ◽  
Piers M. Forster ◽  
Øivind Hodnebrog ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Black Carbon ◽  
Temperature Response ◽  
Weak Surface ◽  
Carbon Concentrations

scholarly journals Understanding the surface temperature response and its uncertainty to CO<sub>2</sub>, CH<sub>4</sub>, black carbon, and sulfate

2021 ◽  
Vol 21 (19) ◽  
pp. 14941-14958
Author(s):  
Kalle Nordling ◽  
Hannele Korhonen ◽  
Jouni Räisänen ◽  
Antti-Ilari Partanen ◽  
Bjørn H. Samset ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Black Carbon ◽  
Surface Albedo ◽  
Climate Models ◽  
Temperature Response ◽  
Regional Model ◽  
Climate Forcing ◽  
Clear Sky ◽  
Temperature Responses ◽  
Global Surface

Abstract. Understanding the regional surface temperature responses to different anthropogenic climate forcing agents, such as greenhouse gases and aerosols, is crucial for understanding past and future regional climate changes. In modern climate models, the regional temperature responses vary greatly for all major forcing agents, but the causes of this variability are poorly understood. Here, we analyze how changes in atmospheric and oceanic energy fluxes due to perturbations in different anthropogenic climate forcing agents lead to changes in global and regional surface temperatures. We use climate model data on idealized perturbations in four major anthropogenic climate forcing agents (CO2, CH4, sulfate, and black carbon aerosols) from Precipitation Driver Response Model Intercomparison Project (PDRMIP) climate experiments for six climate models (CanESM2, HadGEM2-ES, NCAR-CESM1-CAM4, NorESM1, MIROC-SPRINTARS, GISS-E2). Particularly, we decompose the regional energy budget contributions to the surface temperature responses due to changes in longwave and shortwave fluxes under clear-sky and cloudy conditions, surface albedo changes, and oceanic and atmospheric energy transport. We also analyze the regional model-to-model temperature response spread due to each of these components. The global surface temperature response stems from changes in longwave emissivity for greenhouse gases (CO2 and CH4) and mainly from changes in shortwave clear-sky fluxes for aerosols (sulfate and black carbon). The global surface temperature response normalized by effective radiative forcing is nearly the same for all forcing agents (0.63, 0.54, 0.57, 0.61 K W−1 m2). While the main physical processes driving global temperature responses vary between forcing agents, for all forcing agents the model-to-model spread in temperature responses is dominated by differences in modeled changes in longwave clear-sky emissivity. Furthermore, in polar regions for all forcing agents the differences in surface albedo change is a key contributor to temperature responses and its spread. For black carbon, the modeled differences in temperature response due to shortwave clear-sky radiation are also important in the Arctic. Regional model-to-model differences due to changes in shortwave and longwave cloud radiative effect strongly modulate each other. For aerosols, clouds play a major role in the model spread of regional surface temperature responses. In regions with strong aerosol forcing, the model-to-model differences arise from shortwave clear-sky responses and are strongly modulated by combined temperature responses to oceanic and atmospheric heat transport in the models.

scholarly journals Distinct surface response to black carbon aerosols

2021 ◽  
Vol 21 (18) ◽  
pp. 13797-13809
Author(s):  
Tao Tang ◽  
Drew Shindell ◽  
Yuqiang Zhang ◽  
Apostolos Voulgarakis ◽  
Jean-Francois Lamarque ◽  
...  
Keyword(s):  
Wind Speed ◽  
Surface Energy ◽  
Greenhouse Gases ◽  
Surface Temperature ◽  
Black Carbon ◽  
Temperature Response ◽  
Radiative Heating ◽  
Energy Redistribution ◽  
Enhanced Stability ◽  
Reduced Surface

Abstract. For the radiative impact of individual climate forcings, most previous studies focused on the global mean values at the top of the atmosphere (TOA), and less attention has been paid to surface processes, especially for black carbon (BC) aerosols. In this study, the surface radiative responses to five different forcing agents were analyzed by using idealized model simulations. Our analyses reveal that for greenhouse gases, solar irradiance, and scattering aerosols, the surface temperature changes are mainly dictated by the changes of surface radiative heating, but for BC, surface energy redistribution between different components plays a more crucial role. Globally, when a unit BC forcing is imposed at TOA, the net shortwave radiation at the surface decreases by -5.87±0.67 W m−2 (W m−2)−1 (averaged over global land without Antarctica), which is partially offset by increased downward longwave radiation (2.32±0.38 W m−2 (W m−2)−1 from the warmer atmosphere, causing a net decrease in the incoming downward surface radiation of -3.56±0.60 W m−2 (W m−2)−1. Despite a reduction in the downward radiation energy, the surface air temperature still increases by 0.25±0.08 K because of less efficient energy dissipation, manifested by reduced surface sensible (-2.88±0.43 W m−2 (W m−2)−1) and latent heat flux (-1.54±0.27 W m−2 (W m−2)−1), as well as a decrease in Bowen ratio (-0.20±0.07 (W m−2)−1). Such reductions of turbulent fluxes can be largely explained by enhanced air stability (0.07±0.02 K (W m−2)−1), measured as the difference of the potential temperature between 925 hPa and surface, and reduced surface wind speed (-0.05±0.01 m s−1 (W m−2)−1). The enhanced stability is due to the faster atmospheric warming relative to the surface, whereas the reduced wind speed can be partially explained by enhanced stability and reduced Equator-to-pole atmospheric temperature gradient. These rapid adjustments under BC forcing occur in the lower atmosphere and propagate downward to influence the surface energy redistribution and thus surface temperature response, which is not observed under greenhouse gases or scattering aerosols. Our study provides new insights into the impact of absorbing aerosols on surface energy balance and surface temperature response.

scholarly journals Distinct surface response to black carbon aerosols

2021 ◽  
Author(s):  
Tao Tang ◽  
Drew Shindell ◽  
Yuqiang Zhang ◽  
Apostolos Voulgarakis ◽  
Jean-Francois Lamarque ◽  
...  
Keyword(s):  
Wind Speed ◽  
Surface Energy ◽  
Surface Temperature ◽  
Black Carbon ◽  
Temperature Response ◽  
Energy Redistribution ◽  
Carbon Aerosols ◽  
Enhanced Stability ◽  
Reduced Surface ◽  
Black Carbon Aerosols

Abstract. For the radiative impact of individual climate forcings, most previous studies focused on the global mean values at the top of the atmosphere (TOA) and less attention has been paid to surface processes, especially for black carbon aerosols. In this study, the surface radiative responses to five different forcing agents were analyzed by using idealized model simulations. Our analyses reveal that for greenhouse gases, solar irradiance and scattering aerosols, the surface temperature changes are mainly dictated by the changes of surface radiative heating, but for BC, surface energy redistribution between different components plays a more crucial role. Globally, when a unit BC forcing was imposed at TOA, the net shortwave radiation at the surface decreased by 5.09 ± 1.80 W m−2 (averaged over global land), which is partially offset by increased downward longwave radiation (1.67 ± 0.24 W m−2) from the warmer atmosphere, causing a net decrease in the incoming downward surface radiation of 3.42 ± 0.51 W m−2. Despite a reduction in the downward radiation energy, the surface air temperature still increased by 0.14 ± 0.05 K because of less efficient energy dissipation, manifested by reduced surface sensible (2.53 ± 0.37 W m−2) and latent heat flux (1.30 ± 0.27 W m−2), as well as a decrease of Bowen ratio (0.18 ± 0.05). Such reductions of turbulent fluxes can be largely explained by enhanced air stability (0.06 ± 0.01 K), measured as the difference of the potential temperature between 925 hPa and surface, and reduced surface wind speed (0.05 ± 0.01 m s−1). The enhanced stability is due to the faster atmospheric warming relative to the surface whereas the reduced wind speed can be partially explained by enhanced stability and reduced equator-to-pole atmospheric temperature gradient. These rapid adjustments under BC forcing exerted a “top-down” impact on the surface energy redistribution and thus, surface temperature response, which is not observed under greenhouse gas or scattering aerosols. Our study provides new insights into the impact of absorbing aerosols on surface energy balance and surface temperature response.

scholarly journals Understanding the surface temperature response and its uncertainty to CO<sub>2</sub>, CH<sub>4</sub>, black carbon and sulfate

2021 ◽  
Author(s):  
Kalle Nordling ◽  
Hannele Korhonen ◽  
Jouni Räisänen ◽  
Antti-Ilari Partanen ◽  
Bjørn Samset ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Black Carbon ◽  
Surface Albedo ◽  
Climate Models ◽  
Temperature Response ◽  
Regional Model ◽  
Climate Forcing ◽  
Clear Sky ◽  
Temperature Responses ◽  
Global Surface

Abstract. Understanding the regional surface temperature responses to different anthropogenic climate forcing agents, such as greenhouse gases and aerosols, is crucial for understanding past and future regional climate changes. In modern climate models, the regional temperature responses vary greatly for all major forcing agents, but the causes of this variability are poorly understood. Here, we analyse how changes in atmospheric and oceanic energy fluxes due to perturbations in different anthropogenic climate forcing agents lead to changes in global and regional surface temperatures. We use climate model data on idealized perturbations in four major anthropogenic climate forcing agents (CO2, CH4, and sulfate and black carbon aerosols) from PDRMIP climate experiments for six climate models (CanESM2, HadGEM2-ES, NCAR-CESM1-CAM4, NorESM1, MIROC-SPRINTARS, GISS-E2). Particularly, we decompose the regional energy budget contributions to the surface temperature responses due to changes in longwave and shortwave fluxes under clear-sky and cloudy conditions, surface albedo changes, and oceanic and atmospheric energy transport. We also analyse the regional model-to-model temperature response spread due to each of these components. The global surface temperature response stems from changes in longwave emissivity for greenhouse gases (CO2 and CH4) and mainly from changes in shortwave clear-sky fluxes for aerosols (sulfate and black carbon). The global surface temperature response normalized by effective radiative forcing is nearly the same for all forcing agents (0.63, 0.54, 0.57, 0.61 KW−1 m2). While the main physical processes driving global temperature responses vary between forcing agents, for all forcing agents the model-to-model spread in temperature responses is dominated by differences in modelled changes in longwave clear-sky emissivity. Furthermore, in polar regions for all forcing agents the differences in surface albedo change is a key contributor to temperature responses and its spread. For black carbon the modelled differences in temperature response due to shortwave clear-sky radiation are also important in the Arctic. Regional model-to-model differences due to changes in shortwave and longwave cloud radiative effect strongly modulate each other. For aerosols clouds play a major role in the model spread of regional surface temperature responses. In regions with strong aerosol forcing the model-to-model differences arise from shortwave clear-sky responses and are strongly modulated by combined temperature responses to oceanic and atmospheric heat transport in the models.

scholarly journals Traffic Density-Related Black Carbon Distribution: Impact of Wind in a Basin Town

2021 ◽  
Vol 18 (12) ◽  
pp. 6490
Author(s):  
Borut Jereb ◽  
Brigita Gajšek ◽  
Gregor Šipek ◽  
Špela Kovše ◽  
Matevz Obrecht
Keyword(s):  
Black Carbon ◽  
Carbon Concentration ◽  
Ground Level ◽  
Traffic Density ◽  
Carbon Distribution ◽  
Wind Speeds ◽  
Black Carbon Concentration ◽  
Low Wind Speeds ◽  
Temperature Inversions ◽  
Carbon Concentrations

Black carbon is one of the riskiest particle matter pollutants that is harmful to human health. Although it has been increasingly investigated, factors that depend on black carbon distribution and concentration are still insufficiently researched. Variables, such as traffic density, wind speeds, and ground levels can lead to substantial variations of black carbon concentrations and potential exposure, which is even riskier for people living in less-airy sites. Therefore, this paper “fills the gaps” by studying black carbon distribution variations, concentrations, and oscillations, with special emphasis on traffic density and road segments, at multiple locations, in a small city located in a basin, with frequent temperature inversions and infrequent low wind speeds. As wind speed has a significant impact on black carbon concentration trends, it is critical to present how low wind speeds influence black carbon dispersion in a basin city, and how black carbon is dependent on traffic density. Our results revealed that when the wind reached speeds of 1 ms−1, black carbon concentrations actually increased. In lengthy wind periods, when wind speeds reached 2 or 3 ms−1, black carbon concentrations decreased during rush hour and in the time of severe winter biomass burning. By observing the results, it could be concluded that black carbon persists longer in higher altitudes than near ground level. Black carbon concentration oscillations were also seen as more pronounced on main roads with higher traffic density. The more the traffic decreases and becomes steady, the more black carbon concentrations oscillate.

scholarly journals The relevance of mid-Holocene Arctic warming to the future

2019 ◽  
Vol 15 (4) ◽  
pp. 1375-1394 ◽  
Author(s):  
Masakazu Yoshimori ◽  
Marina Suzuki
Keyword(s):  
Surface Temperature ◽  
General Circulation ◽  
Temperature Response ◽  
Longwave Radiation ◽  
General Circulation Models ◽  
Cross Model ◽  
Arctic Warming ◽  
Temperature Changes ◽  
The Future ◽  
Arctic Climate Change

Abstract. There remain substantial uncertainties in future projections of Arctic climate change. There is a potential to constrain these uncertainties using a combination of paleoclimate simulations and proxy data, but such a constraint must be accompanied by physical understanding on the connection between past and future simulations. Here, we examine the relevance of an Arctic warming mechanism in the mid-Holocene (MH) to the future with emphasis on process understanding. We conducted a surface energy balance analysis on 10 atmosphere and ocean general circulation models under the MH and future Representative Concentration Pathway (RCP) 4.5 scenario forcings. It is found that many of the dominant processes that amplify Arctic warming over the ocean from late autumn to early winter are common between the two periods, despite the difference in the source of the forcing (insolation vs. greenhouse gases). The positive albedo feedback in summer results in an increase in oceanic heat release in the colder season when the atmospheric stratification is strong, and an increased greenhouse effect from clouds helps amplify the warming during the season with small insolation. The seasonal progress was elucidated by the decomposition of the factors associated with sea surface temperature, ice concentration, and ice surface temperature changes. We also quantified the contribution of individual components to the inter-model variance in the surface temperature changes. The downward clear-sky longwave radiation is one of major contributors to the model spread throughout the year. Other controlling terms for the model spread vary with the season, but they are similar between the MH and the future in each season. This result suggests that the MH Arctic change may not be analogous to the future in some seasons when the temperature response differs, but it is still useful to constrain the model spread in the future Arctic projection. The cross-model correlation suggests that the feedbacks in preceding seasons should not be overlooked when determining constraints, particularly summer sea ice cover for the constraint of autumn–winter surface temperature response.

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