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  • 2015-2019  (11)
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  • 1
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    Sulfur injections for a cooler planet (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-07-21
    Keywords: Engineering
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Radiative and climate impacts of a large volcanic eruption during stratospheric sulfur geoengineering (2015)
    Copernicus
    Details
    Publication Date: 2015-08-12
    Description: Both explosive volcanic eruptions, which emit sulfur dioxide into the stratosphere, and stratospheric geoengineering via sulfur injections can potentially cool the climate by increasing the amount of scattering particles in the atmosphere. Here we employ a global aerosol-climate model and an earth system model to study the radiative and climate impacts of an erupting volcano during solar radiation management (SRM). According to our simulations, the radiative impacts of an eruption and SRM are not additive: in the simulated case of concurrent eruption and SRM, the peak increase in global forcing is about 40 % lower compared to a corresponding eruption into a clean background atmosphere. In addition, the recovery of the stratospheric sulfate burden and forcing was significantly faster in the concurrent case since the sulfate particles grew larger and thus sedimented faster from the stratosphere. In our simulation where we assumed that SRM would be stopped immediately after a volcano eruption, stopping SRM decreased the overall stratospheric aerosol load. For the same reasons, a volcanic eruption during SRM lead to only about 1/3 of the peak global ensemble-mean cooling compared to an eruption under unperturbed atmospheric conditions. Furthermore, the global cooling signal was seen only for 12 months after the eruption in the former scenario compared to over 40 months in the latter. In terms of the global precipitation rate, we obtain a 36 % smaller decrease in the first year after the eruption and again a clearly faster recovery in the concurrent eruption and SRM scenario. We also found that an explosive eruption could lead to significantly different regional climate responses depending on whether it takes place during geoengineering or into an unperturbed background atmosphere. Our results imply that observations from previous large eruptions, such as Mt Pinatubo in 1991, are not directly applicable when estimating the potential consequences of a volcanic eruption during stratospheric geoengineering.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 3
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    What is the limit of stratospheric sulfur climate engineering? (2015)
    Copernicus
    Details
    Publication Date: 2015-04-15
    Description: The injection of sulfur dioxide (SO2) into the stratosphere to form an artificial stratospheric aerosol layer is considered as an option for solar radiation management. The related reduction in radiative forcing depends upon the amount injected of sulfur dioxide but aerosol model studies indicate a decrease in forcing efficiency with increasing injection magnitude. None of these studies, however, consider injection strengths greater than 10 Tg(S) yr-1. This would be necessary to counteract the strong anthropogenic forcing expected if "business as usual" emission conditions continue throughout this century. To understand the effects of the injection of larger amounts of SO2 we have calculated the effects of SO2 injections up to 100 Tg(S) yr-1. We estimate the reliability of our results through consideration of various injection strategies, and from comparison with results obtained from other models. Our calculations show that the efficiency of the aerosol layer, expressed as the relationship between sulfate aerosol forcing and injection strength, decays exponentially. This result implies that the solar radiation management strategy required to keep temperatures constant at that anticipated for 2020, whilst maintaining "business as usual" conditions, would require atmospheric injections of the order of 45 Tg(S) yr-1 which amounts to 6 times that emitted from of the Mt. Pinatubo eruption each year.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 4
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    The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6): simulation design and preliminary results (2015)
    Copernicus
    Details
    Publication Date: 2015-06-22
    Description: We present a suite of new climate model experiment designs for the Geoengineering Model Intercomparison Project (GeoMIP). This set of experiments, named GeoMIP6 (to be consistent with the Coupled Model Intercomparison Project Phase 6), builds on the previous GeoMIP simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more longwave radiation to escape to space. We discuss experiment designs, as well as the rationale for those designs, showing preliminary results from individual models when available. We also introduce a new feature, called the GeoMIP Testbed, which provides a platform for simulations that will be performed with a few models and subsequently assessed to determine whether the proposed experiment designs will be adopted as core (Tier 1) GeoMIP experiments. This is meant to encourage various stakeholders to propose new targeted experiments that address their key open science questions, with the goal of making GeoMIP more relevant to a broader set of communities.
    Print ISSN: 1991-9611
    Electronic ISSN: 1991-962X
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 5
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    The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6): simulation design and preliminary results (2015)
    Copernicus
    Details
    Publication Date: 2015-10-27
    Description: We present a suite of new climate model experiment designs for the Geoengineering Model Intercomparison Project (GeoMIP). This set of experiments, named GeoMIP6 (to be consistent with the Coupled Model Intercomparison Project Phase 6), builds on the previous GeoMIP project simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more longwave radiation to escape to space. We discuss experiment designs, as well as the rationale for those designs, showing preliminary results from individual models when available. We also introduce a new feature, called the GeoMIP Testbed, which provides a platform for simulations that will be performed with a few models and subsequently assessed to determine whether the proposed experiment designs will be adopted as core (Tier 1) GeoMIP experiments. This is meant to encourage various stakeholders to propose new targeted experiments that address their key open science questions, with the goal of making GeoMIP more relevant to a broader set of communities.
    Print ISSN: 1991-959X
    Electronic ISSN: 1991-9603
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 6
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    A new Geoengineering Model Intercomparison Project (GeoMIP) experiment designed for climate and chemistry models (2015)
    Copernicus
    Details
    Publication Date: 2015-01-15
    Description: A new Geoengineering Model Intercomparison Project (GeoMIP) experiment "G4 specified stratospheric aerosols" (short name: G4SSA) is proposed to investigate the impact of stratospheric aerosol geoengineering on atmosphere, chemistry, dynamics, climate, and the environment. In contrast to the earlier G4 GeoMIP experiment, which requires an emission of sulfur dioxide (SO2) into the model, a prescribed aerosol forcing file is provided to the community, to be consistently applied to future model experiments between 2020 and 2100. This stratospheric aerosol distribution, with a total burden of about 2 Tg S has been derived using the ECHAM5-HAM microphysical model, based on a continuous annual tropical emission of 8 Tg SO2 yr−1. A ramp-up of geoengineering in 2020 and a ramp-down in 2070 over a period of 2 years are included in the distribution, while a background aerosol burden should be used for the last 3 decades of the experiment. The performance of this experiment using climate and chemistry models in a multi-model comparison framework will allow us to better understand the impact of geoengineering and its abrupt termination after 50 years in a changing environment. The zonal and monthly mean stratospheric aerosol input data set is available at https://www2.acd.ucar.edu/gcm/geomip-g4-specified-stratospheric-aerosol-data-set.
    Print ISSN: 1991-959X
    Electronic ISSN: 1991-9603
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
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    Climate extremes in multi-model simulations of stratospheric aerosol and marine cloud brightening climate engineering (2015)
    Copernicus
    Details
    Publication Date: 2015-08-27
    Description: Simulations from a multi-model ensemble for the RCP4.5 climate change scenario for the 21st century, and for two solar radiation management (SRM) schemes (stratospheric sulfate injection (G3), SULF and marine cloud brightening by sea salt emission SALT) have been analysed in terms of changes in the mean and extremes of surface air temperature and precipitation. The climate engineering and termination periods are investigated. During the climate engineering period, both schemes, as intended, offset temperature increases by about 60 % globally, but are more effective in the low latitudes and exhibit some residual warming in the Arctic (especially in the case of SALT which is only applied in the low latitudes). In both climate engineering scenarios, extreme temperature changes are similar to the mean temperature changes over much of the globe. The exceptions are the mid- and high latitudes in the Northern Hemisphere, where high temperatures (90th percentile of the distribution) of the climate engineering period compared to RCP4.5 control period rise less than the mean, and cold temperatures (10th percentile), much more than the mean. This aspect of the SRM schemes is also reflected in simulated reduction in the frost day frequency of occurrence for both schemes. However, summer day frequency of occurrence increases less in the SALT experiment than the SULF experiment, especially over the tropics. Precipitation extremes in the two SRM scenarios act differently – the SULF experiment more effectively mitigates extreme precipitation increases over land compared to the SALT experiment. A reduction in dry spell occurrence over land is observed in the SALT experiment. The SULF experiment has a slight increase in the length of dry spells. A strong termination effect is found for the two climate engineering schemes, with large temperature increases especially in the Arctic. Globally, SULF is more effective in reducing extreme temperature increases over land than SALT. Extreme precipitation increases over land is also more reduced in SULF than the SALT experiment. However, globally SALT decreases the frequency of dry spell length and reduces the occurrence of hot days compared to SULF.
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 8
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    What is the limit of climate engineering by stratospheric injection of SO2? (2015)
    Copernicus
    Details
    Publication Date: 2015-08-18
    Description: The injection of sulfur dioxide (SO2) into the stratosphere to form an artificial stratospheric aerosol layer is discussed as an option for solar radiation management. The related reduction of radiative forcing depends upon the injected amount of sulfur dioxide, but aerosol model studies indicate a decrease in forcing efficiency with increasing injection rate. None of these studies, however, consider injection rates greater than 20 Tg(S) yr−1. But this would be necessary to counteract the strong anthropogenic forcing expected if "business as usual" emission conditions continue throughout this century. To understand the effects of the injection of larger amounts of SO2, we have calculated the effects of SO2 injections up to 100 Tg(S) yr−1. We estimate the reliability of our results through consideration of various injection strategies and from comparison with results obtained from other models. Our calculations show that the efficiency of such a geoengineering method, expressed as the ratio between sulfate aerosol forcing and injection rate, decays exponentially. This result implies that the sulfate solar radiation management strategy required to keep temperatures constant at that anticipated for 2020, while maintaining business as usual conditions, would require atmospheric injections of approximately 45 Tg(S) yr−1 (±15 % or 7 Tg(S) yr−1) at a height corresponding to 60 hPa. This emission is equivalent to 5 to 7 times the Mt. Pinatubo eruption each year.
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 9
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    Radiative and climate impacts of a large volcanic eruption during stratospheric sulfur geoengineering (2016)
    Copernicus
    Details
    Publication Date: 2016-01-18
    Description: Both explosive volcanic eruptions, which emit sulfur dioxide into the stratosphere, and stratospheric geoengineering via sulfur injections can potentially cool the climate by increasing the amount of scattering particles in the atmosphere. Here we employ a global aerosol-climate model and an Earth system model to study the radiative and climate changes occurring after an erupting volcano during solar radiation management (SRM). According to our simulations the radiative impacts of the eruption and SRM are not additive and the radiative effects and climate changes occurring after the eruption depend strongly on whether SRM is continued or suspended after the eruption. In the former case, the peak burden of the additional stratospheric sulfate as well as changes in global mean precipitation are fairly similar regardless of whether the eruption takes place in a SRM or non-SRM world. However, the maximum increase in the global mean radiative forcing caused by the eruption is approximately 21 % lower compared to a case when the eruption occurs in an unperturbed atmosphere. In addition, the recovery of the stratospheric sulfur burden and radiative forcing is significantly faster after the eruption, because the eruption during the SRM leads to a smaller number and larger sulfate particles compared to the eruption in a non-SRM world. On the other hand, if SRM is suspended immediately after the eruption, the peak increase in global forcing caused by the eruption is about 32 % lower compared to a corresponding eruption into a clean background atmosphere. In this simulation, only about one-third of the global ensemble-mean cooling occurs after the eruption, compared to that occurring after an eruption under unperturbed atmospheric conditions. Furthermore, the global cooling signal is seen only for the 12 months after the eruption in the former scenario compared to over 40 months in the latter. In terms of global precipitation rate, we obtain a 36 % smaller decrease in the first year after the eruption and again a clearly faster recovery in the concurrent eruption and SRM scenario, which is suspended after the eruption. We also found that an explosive eruption could lead to significantly different regional climate responses depending on whether it takes place during geoengineering or into an unperturbed background atmosphere. Our results imply that observations from previous large eruptions, such as Mount Pinatubo in 1991, are not directly applicable when estimating the potential consequences of a volcanic eruption during stratospheric geoengineering.
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
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    Geo-Engineering. Untersuchung und Bewertung von Methoden zum Geo-Engineering, die die Zusammensetzung der Atmosphäre beeinflussen (2016)
    In:  Texte / Umweltbundesamt
    Details
    Publication Date: 2023-07-18
    Description: In dieser Arbeit wird der Einfluss von sogenanntem stratosphärischen Geoengineering auf die Ozonschicht der Stratosphäre mit globalen Zirkulationsmodellen untersucht. Stratosphärisches Geoengineering soll einen globalen Abkühlungseffekt erzeugen, welcher der globalen Erwärmung entgegenwirken soll. Momentane Schätzungen gehen davon aus, dass dazu jährliche Injektionen in der Größenordnung von 1-10 Mt Schwefel notwendig sind. Diesen Schätzungen entsprechend werden Sensitivitätsstudien durchgeführt, die den Einfluss auf die Ozonschicht in Funktion der Injektionsrate und einiger Schlüsselparametern zu quantifizieren suchen.Die Ergebnisse zeigen einen sehr komplexen Zusammenhang zwischen den beteiligten Prozessen. Insbesondere dem Zusammenspiel zwischen den Strahlungseigenschaften des Sulfataerosols, der stratosphärischen Zirkulation, den Polarwirbeln, und der Ozon- und Aerosolchemie scheint eine Schlüsselrolle zuzukommen. Unsere Berechnungen ergeben, dass über den Subtropen durch chemische Effekte mit einer Zunahme der Ozonschicht um bis zu 5% zu rechnen ist, während über den Polargebieten und den gemäßigten Breiten vorwiegend eine Abnahme der Ozonkonzentration um bis zu 10% zu erwarten ist. Die Resultate sind jedoch mit großen Unsicherheiten behaftet, die eine korrekte Quantifikation der Implikationen des Geoengineering auf die Ozonschicht mittels Modellexperimenten als wenig wahrscheinlich erscheinen lassen.
    Description: This study investigates the influence of so-called stratospheric geoengineering on the global stratospheric ozone layer with global modeling tools. Stratospheric geoengineering is bound to produce a global cooling effect that is supposed to counterbalance to a certain extend the global warming trend due to anthropogenic greenhouse gas emissions. Current estimations assume that yearly injections of some 1-10 Mt sulphur equivalents are necessary to obtain the desired effect. In accordance to these estimations, we carry out sensitivity studies that that aim at quantifying the effects on the ozone layer as a function of the injection rate and certain key parameters and uncertainties.The results show a very complex linkage of the involved processes that determine the ozone layer. In particular, the interactions among the radiative properties of the sulphate aerosol, stratospheric circulation, the polar vortexes, and aerosol and ozone chemistry seem to be a key. Whereas chemical processes over the subtropical areas appear to induce an enhancement of the ozone layer of up to 5%, high latitudes and the polar areas seem to be up for a depletion of the ozone layer of up to 10%. However, these results are bound to a considerable amount of uncertainty of multiple origins, such that a reliable estimation of the implications of stratospheric geoengineering to the ozone layer may not at all be obtained with model experiments.
    Language: German
    Type: info:eu-repo/semantics/report
    Format: application/pdf
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