W.A. (Liam) Megill
info
Please Note
<p>This page displays the records of the person named above and is not linked to a unique person identifier. This record may need to be merged to a profile.</p>
6 records found
1
Review
(2026)
-
Volker Grewe, Svitlana Zhukovska, Katrin Dahlmann, Sigrun Matthes, Liam Megill, Pascal Bertram, Patrick Ratei, Prajwal Prakasha, Florian Linke, More Authors
The climate impact of aviation resulting from both emissions and effects is gaining attention from aviation stakeholders seeking to identify potential mitigation options. There is a need to consolidate the use of assessment methods and climate metrics, which are required to convert aviation effects into -equivalent emissions. We provide an overview of the operational, technological and scenario-based climate impact assessment methods that have been applied in literature as well as considerations and requirements for the choice of climate metric. We propose a four-layer technology climate impact assessment methodology, which includes: (1) the technology parameters, such as entry into service and temporal and spatial network use; (2) the calculation of three-dimensional aircraft trajectories and emission inventories; (3) the calculation of radiative forcing and induced temperature change time series; and (4) the overall climate impact, measured using a climate metric. We recommend two climate metrics that best fulfill the requirements, the Average Temperature Response (ATR100) and the Efficacy-weighted Global Warming Potential (EGWP100), both over 100 years. Additionally, we discuss further steps, such as the understanding of the most sensitive parameters in this approach, how uncertainties can be included to provide robust estimates, aspects of verification and update possibilities for new findings in research.
...
The climate impact of aviation resulting from both emissions and effects is gaining attention from aviation stakeholders seeking to identify potential mitigation options. There is a need to consolidate the use of assessment methods and climate metrics, which are required to convert aviation effects into -equivalent emissions. We provide an overview of the operational, technological and scenario-based climate impact assessment methods that have been applied in literature as well as considerations and requirements for the choice of climate metric. We propose a four-layer technology climate impact assessment methodology, which includes: (1) the technology parameters, such as entry into service and temporal and spatial network use; (2) the calculation of three-dimensional aircraft trajectories and emission inventories; (3) the calculation of radiative forcing and induced temperature change time series; and (4) the overall climate impact, measured using a climate metric. We recommend two climate metrics that best fulfill the requirements, the Average Temperature Response (ATR100) and the Efficacy-weighted Global Warming Potential (EGWP100), both over 100 years. Additionally, we discuss further steps, such as the understanding of the most sensitive parameters in this approach, how uncertainties can be included to provide robust estimates, aspects of verification and update possibilities for new findings in research.
International civil aviation is the cornerstone of global mobility and trade, enabling the efficient movement of people and goods across long distances. At the same time, global air transport operations contribute to anthropogenic climate change through carbon dioxide (CO2) emissions and a range of non-CO2 emissions and effects. Particularly important is the increased cloudiness due to the formation of condensation trails, or contrails, which is estimated to account for around half of aviation's total radiative forcing. As the industry continues to grow and its climate impact increases, policymakers are increasingly considering the inclusion of aviation non-CO2 effects within regulatory frameworks. This poses a significant challenge, because these emissions and effects vary strongly with emission location, altitude, season and time of day, have very different atmospheric lifetimes and efficacies and remain subject to considerable scientific uncertainty.
A number of alternative aviation fuels, propulsion technologies and operational concepts have been proposed to reduce the aviation industry's climate impact. Quantifying their long-term effects requires tools capable of simulating large scenario ensembles while adequately representing both CO2 and non-CO2 emissions and effects. Comprehensive climate models offer high fidelity but are computationally expensive, making them impractical for the systematic evaluation of large numbers of aviation scenarios. Response models such as AirClim provide a practical alternative by using pre-computed responses and statistical relationships derived from simulations with more comprehensive climate models. However, existing response models are limited in their applicability to emerging propulsion systems and alternative aviation fuels. This dissertation addresses this challenge through the development and application of the open-source response model OpenAirClim, with a particular focus on contrails. The research has three main objectives: (1) to improve the understanding and modelling of persistent contrail formation within a climatological framework; (2) to enable the consistent assessment of future aviation industry scenarios; and (3) to assess the suitability of climate metrics for representing CO2 and non-CO2 climate effects on a common scale within policy frameworks.
The dissertation begins by investigating the environmental and aircraft-design-dependent factors controlling persistent contrail formation. Using 10 % of all hourly reanalysis data on conventional flight levels within the 2010 decade, the relative importance of these factors is analysed on a climatological timescale for a wide range of aviation fuels and propulsion technologies. Ice supersaturation is found to be the dominant limiting factor for all engine and fuel combinations, underscoring the importance of accurately predicting ice supersaturated regions. Nevertheless, the introduction of novel aviation fuels and propulsion technologies is found to have substantial influence on persistent contrail formation. Compared with a state-of-the-art conventional aircraft, envisioned water vapour extraction technologies could reduce the formation of persistent contrails by up to 85 %, whereas hydrogen-powered aircraft could increase formation by around 50 %. The study demonstrates that the probability of persistent contrail formation can be robustly parameterised as a function of aircraft design and flight altitude, which is a necessary first step for developing a consistent climate assessment for different aviation technologies.
Building on this foundation and using dedicated simulations of the general circulation model ECHAM5-CCMod, a new contrail module is developed for the open-source response model OpenAirClim. The module enables the efficient simulation and attribution of stratospheric-adjusted radiative forcing through a modelling chain that links emission inventories, persistent contrail formation, contrail-cirrus coverage and radiative forcing. The framework allows multiple aircraft and fuels to be simultaneously represented within the same emission inventory and scenario. To quantify the climate impact of emerging propulsion technologies and fuels, the module also includes a first representation of the low-soot regime. A comparison with literature demonstrates its ability to reproduce saturation behaviour under high future air traffic scenarios.
The resulting modelling framework is then applied to integrated aviation scenarios developed by the International Civil Aviation Organization (ICAO) to test its ability to simulate complex, multi-fuel and multi-aircraft scenarios. These scenarios represent a wide range of possible technology and fuel transition pathways for the industry. Global mean temperature change from contrails and CO2 is found not to stabilise within the study horizon for any of the ICAO scenarios, even under the most ambitious transition pathways. The impacts of contrails and CO2 are found to have opposing trends: While improvements in overall propulsion efficiency and the increasing use of alternative aviation fuels reduce lifecycle net CO2 emissions, the probability of persistent contrail formation increases. Therefore, the contrail climate benefit of switching to alternative fuels strongly depends on the modelling approach for the low-soot regime. The results demonstrate that an effective reduction in aviation's climate impact requires the introduction of alternative fuels to be accompanied by dedicated non-CO2 mitigation measures.
Finally, to allow for a complete analysis chain from emissions to policy, the suitability of existing physical climate metrics for representing aviation CO2 and non-CO2 emissions and effects is systematically evaluated. The neutrality, temporal stability, policy compatibility and simplicity of alternatives to the conventional Global Warming Potential (GWP) are investigated using the response model AirClim. The historical dominance of the GWP is found to result in a natural bias towards climate metrics that behave similarly. However, more accurate assessments of existing and future aircraft powered by novel aviation fuels can be achieved using the Average Temperature Response (ATR) or Efficacy-weighted Global Warming Potential (EGWP). While the ATR performs best overall, the EGWP represents a practical compromise and has recently been introduced into European aviation policy.
Overall, this dissertation contributes to the scientific understanding of aviation climate impacts by improving knowledge of the factors governing persistent contrail formation, developing a robust response modelling framework for contrails and identifying suitable climate metrics for use in aviation policy. A central outcome is the OpenAirClim contrail module, an open-source and computationally efficient tool that can be readily adapted and extended. Together with ongoing developments of the OpenAirClim framework, this work is an important step towards enabling consistent and transparent assessments of aviation climate impacts across a wide range of industry scenarios, thereby supporting both scientific analysis and policy implementation. ...
A number of alternative aviation fuels, propulsion technologies and operational concepts have been proposed to reduce the aviation industry's climate impact. Quantifying their long-term effects requires tools capable of simulating large scenario ensembles while adequately representing both CO2 and non-CO2 emissions and effects. Comprehensive climate models offer high fidelity but are computationally expensive, making them impractical for the systematic evaluation of large numbers of aviation scenarios. Response models such as AirClim provide a practical alternative by using pre-computed responses and statistical relationships derived from simulations with more comprehensive climate models. However, existing response models are limited in their applicability to emerging propulsion systems and alternative aviation fuels. This dissertation addresses this challenge through the development and application of the open-source response model OpenAirClim, with a particular focus on contrails. The research has three main objectives: (1) to improve the understanding and modelling of persistent contrail formation within a climatological framework; (2) to enable the consistent assessment of future aviation industry scenarios; and (3) to assess the suitability of climate metrics for representing CO2 and non-CO2 climate effects on a common scale within policy frameworks.
The dissertation begins by investigating the environmental and aircraft-design-dependent factors controlling persistent contrail formation. Using 10 % of all hourly reanalysis data on conventional flight levels within the 2010 decade, the relative importance of these factors is analysed on a climatological timescale for a wide range of aviation fuels and propulsion technologies. Ice supersaturation is found to be the dominant limiting factor for all engine and fuel combinations, underscoring the importance of accurately predicting ice supersaturated regions. Nevertheless, the introduction of novel aviation fuels and propulsion technologies is found to have substantial influence on persistent contrail formation. Compared with a state-of-the-art conventional aircraft, envisioned water vapour extraction technologies could reduce the formation of persistent contrails by up to 85 %, whereas hydrogen-powered aircraft could increase formation by around 50 %. The study demonstrates that the probability of persistent contrail formation can be robustly parameterised as a function of aircraft design and flight altitude, which is a necessary first step for developing a consistent climate assessment for different aviation technologies.
Building on this foundation and using dedicated simulations of the general circulation model ECHAM5-CCMod, a new contrail module is developed for the open-source response model OpenAirClim. The module enables the efficient simulation and attribution of stratospheric-adjusted radiative forcing through a modelling chain that links emission inventories, persistent contrail formation, contrail-cirrus coverage and radiative forcing. The framework allows multiple aircraft and fuels to be simultaneously represented within the same emission inventory and scenario. To quantify the climate impact of emerging propulsion technologies and fuels, the module also includes a first representation of the low-soot regime. A comparison with literature demonstrates its ability to reproduce saturation behaviour under high future air traffic scenarios.
The resulting modelling framework is then applied to integrated aviation scenarios developed by the International Civil Aviation Organization (ICAO) to test its ability to simulate complex, multi-fuel and multi-aircraft scenarios. These scenarios represent a wide range of possible technology and fuel transition pathways for the industry. Global mean temperature change from contrails and CO2 is found not to stabilise within the study horizon for any of the ICAO scenarios, even under the most ambitious transition pathways. The impacts of contrails and CO2 are found to have opposing trends: While improvements in overall propulsion efficiency and the increasing use of alternative aviation fuels reduce lifecycle net CO2 emissions, the probability of persistent contrail formation increases. Therefore, the contrail climate benefit of switching to alternative fuels strongly depends on the modelling approach for the low-soot regime. The results demonstrate that an effective reduction in aviation's climate impact requires the introduction of alternative fuels to be accompanied by dedicated non-CO2 mitigation measures.
Finally, to allow for a complete analysis chain from emissions to policy, the suitability of existing physical climate metrics for representing aviation CO2 and non-CO2 emissions and effects is systematically evaluated. The neutrality, temporal stability, policy compatibility and simplicity of alternatives to the conventional Global Warming Potential (GWP) are investigated using the response model AirClim. The historical dominance of the GWP is found to result in a natural bias towards climate metrics that behave similarly. However, more accurate assessments of existing and future aircraft powered by novel aviation fuels can be achieved using the Average Temperature Response (ATR) or Efficacy-weighted Global Warming Potential (EGWP). While the ATR performs best overall, the EGWP represents a practical compromise and has recently been introduced into European aviation policy.
Overall, this dissertation contributes to the scientific understanding of aviation climate impacts by improving knowledge of the factors governing persistent contrail formation, developing a robust response modelling framework for contrails and identifying suitable climate metrics for use in aviation policy. A central outcome is the OpenAirClim contrail module, an open-source and computationally efficient tool that can be readily adapted and extended. Together with ongoing developments of the OpenAirClim framework, this work is an important step towards enabling consistent and transparent assessments of aviation climate impacts across a wide range of industry scenarios, thereby supporting both scientific analysis and policy implementation. ...
International civil aviation is the cornerstone of global mobility and trade, enabling the efficient movement of people and goods across long distances. At the same time, global air transport operations contribute to anthropogenic climate change through carbon dioxide (CO2) emissions and a range of non-CO2 emissions and effects. Particularly important is the increased cloudiness due to the formation of condensation trails, or contrails, which is estimated to account for around half of aviation's total radiative forcing. As the industry continues to grow and its climate impact increases, policymakers are increasingly considering the inclusion of aviation non-CO2 effects within regulatory frameworks. This poses a significant challenge, because these emissions and effects vary strongly with emission location, altitude, season and time of day, have very different atmospheric lifetimes and efficacies and remain subject to considerable scientific uncertainty.
A number of alternative aviation fuels, propulsion technologies and operational concepts have been proposed to reduce the aviation industry's climate impact. Quantifying their long-term effects requires tools capable of simulating large scenario ensembles while adequately representing both CO2 and non-CO2 emissions and effects. Comprehensive climate models offer high fidelity but are computationally expensive, making them impractical for the systematic evaluation of large numbers of aviation scenarios. Response models such as AirClim provide a practical alternative by using pre-computed responses and statistical relationships derived from simulations with more comprehensive climate models. However, existing response models are limited in their applicability to emerging propulsion systems and alternative aviation fuels. This dissertation addresses this challenge through the development and application of the open-source response model OpenAirClim, with a particular focus on contrails. The research has three main objectives: (1) to improve the understanding and modelling of persistent contrail formation within a climatological framework; (2) to enable the consistent assessment of future aviation industry scenarios; and (3) to assess the suitability of climate metrics for representing CO2 and non-CO2 climate effects on a common scale within policy frameworks.
The dissertation begins by investigating the environmental and aircraft-design-dependent factors controlling persistent contrail formation. Using 10 % of all hourly reanalysis data on conventional flight levels within the 2010 decade, the relative importance of these factors is analysed on a climatological timescale for a wide range of aviation fuels and propulsion technologies. Ice supersaturation is found to be the dominant limiting factor for all engine and fuel combinations, underscoring the importance of accurately predicting ice supersaturated regions. Nevertheless, the introduction of novel aviation fuels and propulsion technologies is found to have substantial influence on persistent contrail formation. Compared with a state-of-the-art conventional aircraft, envisioned water vapour extraction technologies could reduce the formation of persistent contrails by up to 85 %, whereas hydrogen-powered aircraft could increase formation by around 50 %. The study demonstrates that the probability of persistent contrail formation can be robustly parameterised as a function of aircraft design and flight altitude, which is a necessary first step for developing a consistent climate assessment for different aviation technologies.
Building on this foundation and using dedicated simulations of the general circulation model ECHAM5-CCMod, a new contrail module is developed for the open-source response model OpenAirClim. The module enables the efficient simulation and attribution of stratospheric-adjusted radiative forcing through a modelling chain that links emission inventories, persistent contrail formation, contrail-cirrus coverage and radiative forcing. The framework allows multiple aircraft and fuels to be simultaneously represented within the same emission inventory and scenario. To quantify the climate impact of emerging propulsion technologies and fuels, the module also includes a first representation of the low-soot regime. A comparison with literature demonstrates its ability to reproduce saturation behaviour under high future air traffic scenarios.
The resulting modelling framework is then applied to integrated aviation scenarios developed by the International Civil Aviation Organization (ICAO) to test its ability to simulate complex, multi-fuel and multi-aircraft scenarios. These scenarios represent a wide range of possible technology and fuel transition pathways for the industry. Global mean temperature change from contrails and CO2 is found not to stabilise within the study horizon for any of the ICAO scenarios, even under the most ambitious transition pathways. The impacts of contrails and CO2 are found to have opposing trends: While improvements in overall propulsion efficiency and the increasing use of alternative aviation fuels reduce lifecycle net CO2 emissions, the probability of persistent contrail formation increases. Therefore, the contrail climate benefit of switching to alternative fuels strongly depends on the modelling approach for the low-soot regime. The results demonstrate that an effective reduction in aviation's climate impact requires the introduction of alternative fuels to be accompanied by dedicated non-CO2 mitigation measures.
Finally, to allow for a complete analysis chain from emissions to policy, the suitability of existing physical climate metrics for representing aviation CO2 and non-CO2 emissions and effects is systematically evaluated. The neutrality, temporal stability, policy compatibility and simplicity of alternatives to the conventional Global Warming Potential (GWP) are investigated using the response model AirClim. The historical dominance of the GWP is found to result in a natural bias towards climate metrics that behave similarly. However, more accurate assessments of existing and future aircraft powered by novel aviation fuels can be achieved using the Average Temperature Response (ATR) or Efficacy-weighted Global Warming Potential (EGWP). While the ATR performs best overall, the EGWP represents a practical compromise and has recently been introduced into European aviation policy.
Overall, this dissertation contributes to the scientific understanding of aviation climate impacts by improving knowledge of the factors governing persistent contrail formation, developing a robust response modelling framework for contrails and identifying suitable climate metrics for use in aviation policy. A central outcome is the OpenAirClim contrail module, an open-source and computationally efficient tool that can be readily adapted and extended. Together with ongoing developments of the OpenAirClim framework, this work is an important step towards enabling consistent and transparent assessments of aviation climate impacts across a wide range of industry scenarios, thereby supporting both scientific analysis and policy implementation.
A number of alternative aviation fuels, propulsion technologies and operational concepts have been proposed to reduce the aviation industry's climate impact. Quantifying their long-term effects requires tools capable of simulating large scenario ensembles while adequately representing both CO2 and non-CO2 emissions and effects. Comprehensive climate models offer high fidelity but are computationally expensive, making them impractical for the systematic evaluation of large numbers of aviation scenarios. Response models such as AirClim provide a practical alternative by using pre-computed responses and statistical relationships derived from simulations with more comprehensive climate models. However, existing response models are limited in their applicability to emerging propulsion systems and alternative aviation fuels. This dissertation addresses this challenge through the development and application of the open-source response model OpenAirClim, with a particular focus on contrails. The research has three main objectives: (1) to improve the understanding and modelling of persistent contrail formation within a climatological framework; (2) to enable the consistent assessment of future aviation industry scenarios; and (3) to assess the suitability of climate metrics for representing CO2 and non-CO2 climate effects on a common scale within policy frameworks.
The dissertation begins by investigating the environmental and aircraft-design-dependent factors controlling persistent contrail formation. Using 10 % of all hourly reanalysis data on conventional flight levels within the 2010 decade, the relative importance of these factors is analysed on a climatological timescale for a wide range of aviation fuels and propulsion technologies. Ice supersaturation is found to be the dominant limiting factor for all engine and fuel combinations, underscoring the importance of accurately predicting ice supersaturated regions. Nevertheless, the introduction of novel aviation fuels and propulsion technologies is found to have substantial influence on persistent contrail formation. Compared with a state-of-the-art conventional aircraft, envisioned water vapour extraction technologies could reduce the formation of persistent contrails by up to 85 %, whereas hydrogen-powered aircraft could increase formation by around 50 %. The study demonstrates that the probability of persistent contrail formation can be robustly parameterised as a function of aircraft design and flight altitude, which is a necessary first step for developing a consistent climate assessment for different aviation technologies.
Building on this foundation and using dedicated simulations of the general circulation model ECHAM5-CCMod, a new contrail module is developed for the open-source response model OpenAirClim. The module enables the efficient simulation and attribution of stratospheric-adjusted radiative forcing through a modelling chain that links emission inventories, persistent contrail formation, contrail-cirrus coverage and radiative forcing. The framework allows multiple aircraft and fuels to be simultaneously represented within the same emission inventory and scenario. To quantify the climate impact of emerging propulsion technologies and fuels, the module also includes a first representation of the low-soot regime. A comparison with literature demonstrates its ability to reproduce saturation behaviour under high future air traffic scenarios.
The resulting modelling framework is then applied to integrated aviation scenarios developed by the International Civil Aviation Organization (ICAO) to test its ability to simulate complex, multi-fuel and multi-aircraft scenarios. These scenarios represent a wide range of possible technology and fuel transition pathways for the industry. Global mean temperature change from contrails and CO2 is found not to stabilise within the study horizon for any of the ICAO scenarios, even under the most ambitious transition pathways. The impacts of contrails and CO2 are found to have opposing trends: While improvements in overall propulsion efficiency and the increasing use of alternative aviation fuels reduce lifecycle net CO2 emissions, the probability of persistent contrail formation increases. Therefore, the contrail climate benefit of switching to alternative fuels strongly depends on the modelling approach for the low-soot regime. The results demonstrate that an effective reduction in aviation's climate impact requires the introduction of alternative fuels to be accompanied by dedicated non-CO2 mitigation measures.
Finally, to allow for a complete analysis chain from emissions to policy, the suitability of existing physical climate metrics for representing aviation CO2 and non-CO2 emissions and effects is systematically evaluated. The neutrality, temporal stability, policy compatibility and simplicity of alternatives to the conventional Global Warming Potential (GWP) are investigated using the response model AirClim. The historical dominance of the GWP is found to result in a natural bias towards climate metrics that behave similarly. However, more accurate assessments of existing and future aircraft powered by novel aviation fuels can be achieved using the Average Temperature Response (ATR) or Efficacy-weighted Global Warming Potential (EGWP). While the ATR performs best overall, the EGWP represents a practical compromise and has recently been introduced into European aviation policy.
Overall, this dissertation contributes to the scientific understanding of aviation climate impacts by improving knowledge of the factors governing persistent contrail formation, developing a robust response modelling framework for contrails and identifying suitable climate metrics for use in aviation policy. A central outcome is the OpenAirClim contrail module, an open-source and computationally efficient tool that can be readily adapted and extended. Together with ongoing developments of the OpenAirClim framework, this work is an important step towards enabling consistent and transparent assessments of aviation climate impacts across a wide range of industry scenarios, thereby supporting both scientific analysis and policy implementation.
Journal article
(2026)
-
Vanessa Santos Gabriel, Luca Bugliaro, Mara Montag, Sabrina Ries, Ziming Wang, Kai Widmaier, Matteo Arico, Elena de la Torre Castro, Liam Megill, More Authors
Contrails – thin ice clouds formed by aircraft – are a major contributor to aviation-induced climate forcing, yet their observational characterization remains limited. We present a manually labeled contrail dataset derived from observations of the Meteosat Second Generation (MSG) SEVIRI instrument over Europe and the North Atlantic, comprising 140 scenes of 256 × 256 pixels at 3 km nominal resolution. The dataset covers the time period in which Meteosat-10 was the operational satellite (from January 2013 through February 2018 and from March 2023 through March 2024) and scenes are distributed randomly over the whole SEVIRI disk. Each scene was independently annotated by three labelers, with ground truth established via majority consensus. To provide additional context, the dataset includes outputs from two satellite retrievals: CiPS (Cirrus Properties from SEVIRI) and ProPS (Probabilistic Cloud Top Phase retrieval), offering information on cloud cover and cloud top phase, cirrus probability, ice optical thickness, and ice cloud top height. These complementary variables enable detailed investigations, such as factors influencing contrail visibility. The dataset supports analyses of contrail detection, contrail characteristics, cloud-contrail interactions, and environmental conditions affecting detection. By providing high-quality labeled data with auxiliary cloud information, this resource facilitates the development and evaluation of contrail studies, contributes to improved understanding of aviation-related cloud effects, and informs strategies for climate impact mitigation.
...
Contrails – thin ice clouds formed by aircraft – are a major contributor to aviation-induced climate forcing, yet their observational characterization remains limited. We present a manually labeled contrail dataset derived from observations of the Meteosat Second Generation (MSG) SEVIRI instrument over Europe and the North Atlantic, comprising 140 scenes of 256 × 256 pixels at 3 km nominal resolution. The dataset covers the time period in which Meteosat-10 was the operational satellite (from January 2013 through February 2018 and from March 2023 through March 2024) and scenes are distributed randomly over the whole SEVIRI disk. Each scene was independently annotated by three labelers, with ground truth established via majority consensus. To provide additional context, the dataset includes outputs from two satellite retrievals: CiPS (Cirrus Properties from SEVIRI) and ProPS (Probabilistic Cloud Top Phase retrieval), offering information on cloud cover and cloud top phase, cirrus probability, ice optical thickness, and ice cloud top height. These complementary variables enable detailed investigations, such as factors influencing contrail visibility. The dataset supports analyses of contrail detection, contrail characteristics, cloud-contrail interactions, and environmental conditions affecting detection. By providing high-quality labeled data with auxiliary cloud information, this resource facilitates the development and evaluation of contrail studies, contributes to improved understanding of aviation-related cloud effects, and informs strategies for climate impact mitigation.
Mounting evidence has highlighted the role of aviation non-CO2 emissions in anthropogenic climate change. Of particular importance is the impact of contrails, to which recent studies attribute over one-third of the total effective radiative forcing from aircraft operations. However, the relative importance of the aircraft-design-dependent and environmental factors that influence the formation of persistent contrails is not yet well understood. In this paper, we use ERA5 data from the 2010s to better understand the interplay between the factors on a climatological timescale. We identify ice supersaturation as the most limiting factor for all aircraft designs considered, underscoring the importance of accurately estimating ice supersaturated regions. We also develop climatological relationships that describe potential persistent contrail formation as a function of the pressure level and Schmidt-Appleman mixing line slope. We find that the influence of aircraft design on persistent contrail formation reduces with increasing altitude. Compared to a state-of-the-art conventional aircraft with an overall propulsion system efficiency of 0.37, water vapour extraction technologies envisioned for the future have the potential to reduce persistent contrail formation by up to 85.1 %. On the other hand, compared to the same reference, hydrogen combustion and fuel cell aircraft could increase globally averaged persistent contrail formation by 46.5 % and 54.7 % respectively. Due to differing contrail properties, further work is required to translate these changes into climate impacts. This study is a step towards the development of a new and computationally inexpensive method to analyse the contrail climate impact of novel aviation fuels and propulsion technologies.
...
Mounting evidence has highlighted the role of aviation non-CO2 emissions in anthropogenic climate change. Of particular importance is the impact of contrails, to which recent studies attribute over one-third of the total effective radiative forcing from aircraft operations. However, the relative importance of the aircraft-design-dependent and environmental factors that influence the formation of persistent contrails is not yet well understood. In this paper, we use ERA5 data from the 2010s to better understand the interplay between the factors on a climatological timescale. We identify ice supersaturation as the most limiting factor for all aircraft designs considered, underscoring the importance of accurately estimating ice supersaturated regions. We also develop climatological relationships that describe potential persistent contrail formation as a function of the pressure level and Schmidt-Appleman mixing line slope. We find that the influence of aircraft design on persistent contrail formation reduces with increasing altitude. Compared to a state-of-the-art conventional aircraft with an overall propulsion system efficiency of 0.37, water vapour extraction technologies envisioned for the future have the potential to reduce persistent contrail formation by up to 85.1 %. On the other hand, compared to the same reference, hydrogen combustion and fuel cell aircraft could increase globally averaged persistent contrail formation by 46.5 % and 54.7 % respectively. Due to differing contrail properties, further work is required to translate these changes into climate impacts. This study is a step towards the development of a new and computationally inexpensive method to analyse the contrail climate impact of novel aviation fuels and propulsion technologies.
A growing body of research has highlighted the major contribution of aviation non-CO2 emissions and effects to anthropogenic climate change. Regulation of these emissions, for example in the EU Emissions Trading System, requires the use of a climate metric. However, choosing a suitable climate metric is challenging due to the high uncertainties of aviation non-CO2 climate impacts, their variability in atmospheric lifetimes and their dependence on emission location and altitude. Here we use AirClim to explore alternatives to the conventional Global Warming Potential (GWP) by analysing the neutrality, temporal stability, compatibility and simplicity of existing climate metrics and perform a trade-off. We find that using the temperature-based Average Temperature Response (ATR) or using an Efficacy-weighted GWP (EGWP) would enable a more accurate assessment of existing as well as future aircraft powered by novel aviation fuels
...
A growing body of research has highlighted the major contribution of aviation non-CO2 emissions and effects to anthropogenic climate change. Regulation of these emissions, for example in the EU Emissions Trading System, requires the use of a climate metric. However, choosing a suitable climate metric is challenging due to the high uncertainties of aviation non-CO2 climate impacts, their variability in atmospheric lifetimes and their dependence on emission location and altitude. Here we use AirClim to explore alternatives to the conventional Global Warming Potential (GWP) by analysing the neutrality, temporal stability, compatibility and simplicity of existing climate metrics and perform a trade-off. We find that using the temperature-based Average Temperature Response (ATR) or using an Efficacy-weighted GWP (EGWP) would enable a more accurate assessment of existing as well as future aircraft powered by novel aviation fuels
A growing body of research has highlighted the major contribution of aviation non-CO2 emissions to anthropogenic climate change. Regulation of these emissions, for example in the EU Emissions Trading System (ETS), requires the use of a climate metric. However, choosing a suitable climate metric is challenging due to the high uncertainties of aviation non-CO2 climate impacts, their variability in atmospheric lifetimes and their dependence on emission location and altitude. In this study, we explore the neutrality, temporal stability, compatibility and transparency of existing, physical climate metrics and find the Average Temperature Response (ATR) to be most suitable for aviation policy and aircraft design. We show that the similarities of the total CO2-eq emissions calculated by the ATR and the Global Warming Potential (GWP) for current aircraft would enable a timely introduction of the ATR in aviation policy, allowing for a more accurate assessment of novel aviation fuels and aircraft designs.
...
A growing body of research has highlighted the major contribution of aviation non-CO2 emissions to anthropogenic climate change. Regulation of these emissions, for example in the EU Emissions Trading System (ETS), requires the use of a climate metric. However, choosing a suitable climate metric is challenging due to the high uncertainties of aviation non-CO2 climate impacts, their variability in atmospheric lifetimes and their dependence on emission location and altitude. In this study, we explore the neutrality, temporal stability, compatibility and transparency of existing, physical climate metrics and find the Average Temperature Response (ATR) to be most suitable for aviation policy and aircraft design. We show that the similarities of the total CO2-eq emissions calculated by the ATR and the Global Warming Potential (GWP) for current aircraft would enable a timely introduction of the ATR in aviation policy, allowing for a more accurate assessment of novel aviation fuels and aircraft designs.