scholarly journals Surface temperature response to regional Black Carbon emissions: Do location and magnitude matter?

2019 ◽  
Author(s):  
Maria Sand ◽  
Terje K. Berntsen ◽  
Annica Ekman ◽  
Hans-Christen Hansson ◽  
Anna Lewinschal
Keyword(s):  
North America ◽  
Surface Temperature ◽  
South Asia ◽  
Black Carbon ◽  
Temperature Change ◽  
Radiative Forcing ◽  
Sea Surface ◽  
Emission Region ◽  
Regional Temperature ◽  
Fully Coupled

Abstract. Aerosol radiative forcing can influence climate both locally and far outside the emission region. Here we investigate Black Carbon (BC) aerosols emitted in four major emissions areas and evaluate the importance of emission location and magnitude, as well as the concept of the absolute regional temperature-change potentials. We perform simulations with a climate model (NorESM) with a fully coupled ocean and with fixed sea surface temperatures. BC emissions are increased by a rate of 10 and 20 in South Asia, North America and Europe, respectively, and by 5 and 10 in East Asia (due to higher emissions there). We find strikingly similar regional surface temperature responses and geographical patterns per unit BC emission in Europe and North America, but somewhat lower temperature sensitivities for East Asian emissions. BC emitted in South Asia shows a different geographical pattern by changing the Indian monsoon and cooling the surface. Choosing the highest emission rate results in lower surface temperature change per emission unit compared to the lowest rate, but the difference is generally not statistically significant except for the Arctic. An advantage of high-perturbation simulations is the clearer emergence of regional signals. Our results show that the linearity of normalized temperature effects of BC is fairly well preserved despite the relatively large perturbations, but that regional temperature coefficients calculated from high perturbations may be a conservative estimate. Regardless of emission region, BC causes a northward shift of the ITCZ, and this shift is apparent both with fully coupled ocean and with fixed sea surface temperatures. For these regional BC emissions perturbations, we find that the effective radiative forcing is not a good measure of the climate response.

scholarly journals Surface temperature response to regional black carbon emissions: do location and magnitude matter?

2020 ◽  
Vol 20 (5) ◽  
pp. 3079-3089 ◽  
Author(s):  
Maria Sand ◽  
Terje K. Berntsen ◽  
Annica M. L. Ekman ◽  
Hans-Christen Hansson ◽  
Anna Lewinschal
Keyword(s):  
North America ◽  
Surface Temperature ◽  
South Asia ◽  
Radiative Forcing ◽  
Temperature Response ◽  
Sea Surface ◽  
Emission Region ◽  
Surface Temperatures ◽  
Regional Temperature ◽  
Fully Coupled

Abstract. Aerosol radiative forcing can influence climate both locally and far outside the emission region. Here we investigate black carbon (BC) aerosols emitted in four major emission areas and evaluate the importance of emission location and magnitude as well as the concept of the absolute regional temperature-change potentials (ARTP). We perform simulations with a climate model (NorESM) with a fully coupled ocean and with fixed sea surface temperatures. BC emissions for year 2000 are increased by factors of 10 and 20 in South Asia, North America, and Europe, respectively, and by 5 and 10 in East Asia (due to higher emissions there). The perturbed simulations and a reference simulation are run for 100 years with three ensemble members each. We find strikingly similar regional surface temperature responses and geographical patterns per unit BC emission in Europe and North America but somewhat lower temperature sensitivities for East Asian emissions. BC emitted in South Asia shows a different geographical pattern in surface temperatures, by changing the Indian monsoon and cooling the surface. We find that the ARTP approach rather accurately reproduces the fully coupled temperature response of NorESM. Choosing the highest emission rate results in lower surface temperature change per emission unit compared to the lowest rate, but the difference is generally not statistically significant except for the Arctic. An advantage of high-perturbation simulations is the clearer emergence of regional signals. Our results show that the linearity of normalized temperature effects of BC is fairly well preserved despite the relatively large perturbations but that regional temperature coefficients calculated from high perturbations may be a conservative estimate. Regardless of emission region, BC causes a northward shift of the ITCZ, and this shift is apparent both with a fully coupled ocean and with fixed sea surface temperatures. For these regional BC emission perturbations, we find that the effective radiative forcing is not a good measure of the climate response. A limitation of this study is the uncertainties in BC–cloud interactions and the amount of BC absorption, both of which are model dependent.

scholarly journals Local and remote temperature response of regional SO<sub>2</sub> emissions

2018 ◽  
Author(s):  
Anna Lewinschal ◽  
Annica M. L. Ekman ◽  
Hans-Christen Hansson ◽  
Maria Sand ◽  
Terje K. Berntsen ◽  
...  
Keyword(s):  
East Asia ◽  
South Asia ◽  
Temperature Change ◽  
Radiative Forcing ◽  
Regional Scale ◽  
Temperature Response ◽  
The Arctic ◽  
Emission Region ◽  
So2 Emissions ◽  
Emission Changes

Abstract. Short-lived anthropogenic climate forcers, such as sulphate aerosols, affect both climate and air quality. Despite being short-lived, these forcers do not affect temperatures only locally; regions far away from the emission sources are also affected. Climate metrics are often used e.g. in a policy context to compare the climate impact of different anthropogenic forcing agents. These metrics typically relate a forcing change in a certain region with a temperature change in another region and thus often require a separate model to convert emission changes to radiative forcing changes. In this study, we used a coupled Earth System Model (NorESM) to calculate emission-to-temperature-response metrics for sulphur dioxide (SO2) emission changes in four different policy-relevant regions: Europe, North America, East Asia and South Asia. We first increased the SO2 emissions in each individual region by an amount giving approximately the same global average radiative forcing change (−0.45 W m−2). The global mean temperature change per unit sulphur emission compared to the control experiment was independent of emission region and equal to ∼ 0.006 K/TgSyr−1. On a regional scale, the Arctic showed the largest temperature response in all experiments. The second largest temperature change occurred in the region of the imposed emission increase, except when South Asian emissions were changed; in this experiment, the temperature response was approximately the same in South Asia and East Asia. We also examined the non-linearity of the temperature response by removing all anthropogenic SO2 emissions over Europe in one experiment. In this case, the temperature response (both global and regional) was twice of that in the corresponding experiment with a European emission increase. This nonlinearity in the temperature response is one of many uncertainties associated with the use of simplified climate metrics.

scholarly journals Emission metrics for quantifying regional climate impacts of aviation

2017 ◽  
Vol 8 (3) ◽  
pp. 547-563 ◽  
Author(s):  
Marianne T. Lund ◽  
Borgar Aamaas ◽  
Terje Berntsen ◽  
Lisa Bock ◽  
Ulrike Burkhardt ◽  
...  
Keyword(s):  
North America ◽  
Temperature Change ◽  
Radiative Forcing ◽  
Large Scale ◽  
Regional Climate ◽  
Temperature Response ◽  
Climate Impacts ◽  
Source Regions ◽  
Latitudinal Patterns ◽  
Regional Temperature

Abstract. This study examines the impacts of emissions from aviation in six source regions on global and regional temperatures. We consider the NOx-induced impacts on ozone and methane, aerosols and contrail-cirrus formation and calculate the global and regional emission metrics global warming potential (GWP), global temperature change potential (GTP) and absolute regional temperature change potential (ARTP). The GWPs and GTPs vary by a factor of 2–4 between source regions. We find the highest aviation aerosol metric values for South Asian emissions, while contrail-cirrus metrics are higher for Europe and North America, where contrail formation is prevalent, and South America plus Africa, where the optical depth is large once contrails form. The ARTP illustrate important differences in the latitudinal patterns of radiative forcing (RF) and temperature response: the temperature response in a given latitude band can be considerably stronger than suggested by the RF in that band, also emphasizing the importance of large-scale circulation impacts. To place our metrics in context, we quantify temperature change in four broad latitude bands following 1 year of emissions from present-day aviation, including CO2. Aviation over North America and Europe causes the largest net warming impact in all latitude bands, reflecting the higher air traffic activity in these regions. Contrail cirrus gives the largest warming contribution in the short term, but remain important at about 15 % of the CO2 impact in several regions even after 100 years. Our results also illustrate both the short- and long-term impacts of CO2: while CO2 becomes dominant on longer timescales, it also gives a notable warming contribution already 20 years after the emission. Our emission metrics can be further used to estimate regional temperature change under alternative aviation emission scenarios. A first evaluation of the ARTP in the context of aviation suggests that further work to account for vertical sensitivities in the relationship between RF and temperature response would be valuable for further use of the concept.

scholarly journals Emission metrics for quantifying regional climate impacts of aviation

2017 ◽  
Author(s):  
Marianne T. Lund ◽  
Borgar Aamaas ◽  
Terje Berntsen ◽  
Lisa Bock ◽  
Ulrike Burkhardt ◽  
...  
Keyword(s):  
North America ◽  
Temperature Change ◽  
Radiative Forcing ◽  
Large Scale ◽  
Regional Climate ◽  
Temperature Response ◽  
Climate Impacts ◽  
Pulse Emission ◽  
Source Regions ◽  
Regional Temperature

Abstract. This study examines the impacts of emissions from aviation in six source regions on global and regional temperature. We consider the NOx-induced impacts on ozone and methane, aerosols and contrail-cirrus formation, and calculate the global and regional climate metrics Global Warming Potential (GWP), Global Temperature change Potential (GTP) and Absolute Regional Temperature change Potential (ARTP). GWPs and GTPs vary by a factor 2–4 between source regions. We find the highest aviation aerosol metric values for South Asian emissions, while contrail-cirrus metrics are higher for Europe and North America, where contrail formation is prevalent, and South America plus Africa, where the optical depth is large once contrails form. The ARTP illustrate important differences in the latitudinal patterns of radiative forcing (RF) and temperature response: The temperature response in a given latitude band can be considerably stronger than suggested by the RF in that band, also emphasizing the importance of large-scale circulation impacts. To place our metrics in context, we quantify the temperature response in the four broad latitude bands following a one-year pulse emission from present-day aviation, including CO2. Aviation over North America and Europe cause the largest net warming impact in all latitude bands, reflecting the higher air traffic activity here. For all regions, the largest single warming contribution is from contrail-cirrus 20 years after the emissions, while CO2 becomes dominant at 100 years, although contrail-cirrus remain important in several regions also on this time scale. Our emission metrics can be further used to estimate regional temperature impact under alternative aviation emission scenarios. A first evaluation of the ARTP in the context of aviation suggests that further work to account for vertical sensitivities in the relationship between RF and temperature response would be valuable for further use of the concept.

scholarly journals Global and regional temperature-change potentials for near-term climate forcers

2013 ◽  
Vol 13 (5) ◽  
pp. 2471-2485 ◽  
Author(s):  
W. J. Collins ◽  
M. M. Fry ◽  
H. Yu ◽  
J. S. Fuglestvedt ◽  
D. T. Shindell ◽  
...  
Keyword(s):  
South Asia ◽  
Temperature Change ◽  
Temperature Response ◽  
The Arctic ◽  
Emission Region ◽  
Global Average ◽  
Ozone Precursors ◽  
Aerosol Emission ◽  
Regional Temperature ◽  
Near Term

Abstract. We examine the climate effects of the emissions of near-term climate forcers (NTCFs) from 4 continental regions (East Asia, Europe, North America and South Asia) using results from the Task Force on Hemispheric Transport of Air Pollution Source-Receptor global chemical transport model simulations. We address 3 aerosol species (sulphate, particulate organic matter and black carbon) and 4 ozone precursors (methane, reactive nitrogen oxides (NOx), volatile organic compounds and carbon monoxide). We calculate the global climate metrics: global warming potentials (GWPs) and global temperature change potentials (GTPs). For the aerosols these metrics are simply time-dependent scalings of the equilibrium radiative forcings. The GTPs decrease more rapidly with time than the GWPs. The aerosol forcings and hence climate metrics have only a modest dependence on emission region. The metrics for ozone precursors include the effects on the methane lifetime. The impacts via methane are particularly important for the 20 yr GTPs. Emissions of NOx and VOCs from South Asia have GWPs and GTPs of higher magnitude than from the other Northern Hemisphere regions. The analysis is further extended by examining the temperature-change impacts in 4 latitude bands, and calculating absolute regional temperature-change potentials (ARTPs). The latitudinal pattern of the temperature response does not directly follow the pattern of the diagnosed radiative forcing. We find that temperatures in the Arctic latitudes appear to be particularly sensitive to BC emissions from South Asia. The northern mid-latitude temperature response to northern mid-latitude emissions is approximately twice as large as the global average response for aerosol emission, and about 20–30% larger than the global average for methane, VOC and CO emissions.

scholarly journals A Link between the Hiatus in Global Warming and North American Drought

2015 ◽  
Vol 28 (9) ◽  
pp. 3834-3845 ◽  
Author(s):  
Thomas L. Delworth ◽  
Fanrong Zeng ◽  
Anthony Rosati ◽  
Gabriel A. Vecchi ◽  
Andrew T. Wittenberg
Keyword(s):  
Global Warming ◽  
North America ◽  
Surface Temperature ◽  
North American ◽  
Radiative Forcing ◽  
Tropical Pacific ◽  
Global Warming Hiatus ◽  
Warming Hiatus ◽  
The Impact ◽  
The Tropical Pacific

Abstract Portions of western North America have experienced prolonged drought over the last decade. This drought has occurred at the same time as the global warming hiatus—a decadal period with little increase in global mean surface temperature. Climate models and observational analyses are used to clarify the dual role of recent tropical Pacific changes in driving both the global warming hiatus and North American drought. When observed tropical Pacific wind stress anomalies are inserted into coupled models, the simulations produce persistent negative sea surface temperature anomalies in the eastern tropical Pacific, a hiatus in global warming, and drought over North America driven by SST-induced atmospheric circulation anomalies. In the simulations herein the tropical wind anomalies account for 92% of the simulated North American drought during the recent decade, with 8% from anthropogenic radiative forcing changes. This suggests that anthropogenic radiative forcing is not the dominant driver of the current drought, unless the wind changes themselves are driven by anthropogenic radiative forcing. The anomalous tropical winds could also originate from coupled interactions in the tropical Pacific or from forcing outside the tropical Pacific. The model experiments suggest that if the tropical winds were to return to climatological conditions, then the recent tendency toward North American drought would diminish. Alternatively, if the anomalous tropical winds were to persist, then the impact on North American drought would continue; however, the impact of the enhanced Pacific easterlies on global temperature diminishes after a decade or two due to a surface reemergence of warmer water that was initially subducted into the ocean interior.

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