Assessing the Climate Impact of Formation Flights

An operational measure that is inspired by migrant birds aiming toward the mitigation of aviation climate impact is to fly in aerodynamic formation. When this operational measure is adapted to commercial aircraft it saves fuel and is, therefore, expected to reduce the climate impact of aviation. Besides the total emission amount, this mitigation option also changes the location of emissions, impacting the non-CO2 climate effects arising from NOx and H2O emissions and contrails. Here, we assess these non-CO2 climate impacts with a climate response model to assure a benefit for climate not only due to CO2 emission reductions, but also due to reduced non-CO2 effects. Therefore, the climate response model AirClim is used, which includes CO2 effects and also the impact of water vapor and contrail induced cloudiness as well as the impact of nitrogen dioxide emissions on the ozone and methane concentration. For this purpose, AirClim has been adopted to account for saturation effects occurring for formation flight. The results of the case studies show that the implementation of formation flights in the 50 most popular airports for the year 2017 display an average decrease of fuel consumption by 5%. The climate impact, in terms of average near surface temperature change, is estimated to be reduced in average by 24%, with values of individual formations between 13% and 33%.

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A strategy for climate evaluation of aircraft technology: an efficient climate impact assessment tool – AirClim

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-12185-2007 ◽

2007 ◽

Vol 7 (4) ◽

pp. 12185-12229 ◽

Cited By ~ 4

Author(s):

V. Grewe ◽

A. Stenke

Keyword(s):

Climate Change ◽

Radiative Forcing ◽

Climate Impact ◽

Climate Impacts ◽

Assessment Tools ◽

Nox Emissions ◽

Near Surface ◽

Temperature Changes ◽

Concentration Changes ◽

The Impact

Abstract. Climate change is a challenge to society and to cope with requires assessment tools which are suitable to evaluate new technology options with respect to their impact on climate. Here we present AirClim, a model which comprises a linearisation of the processes occurring from the emission to an estimate in near surface temperature change, which is presumed to be a reasonable indicator for climate change. The model is designed to be applicable to aircraft technology, i.e.~the climate agents CO2, H2O, CH4 and O3 (latter two resulting from NOx-emissions) and contrails are taken into account. It employs a number of precalculated atmospheric data and combines them with aircraft emission data to obtain the temporal evolution of atmospheric concentration changes, radiative forcing and temperature changes. The linearisation is based on precalculated data derived from 25 steady-state simulations of the state-of-the-art climate-chemistry model E39/C, which include sustained normalised emissions at various atmospheric regions. The results show that strongest climate impacts from ozone changes occur for emissions in the tropical upper troposphere (60 mW/m²; 80 mK for 1 TgN emitted), whereas from methane in the middle tropical troposphere (–2.7% change in methane lifetime; –30 mK per TgN). The estimate of the temperature changes caused by the individual climate agents takes into account a perturbation lifetime, related to the region of emission. A comparison of this approach with results from the TRADEOFF and SCENIC projects shows reasonable agreement with respect to concentration changes, radiative forcing, and temperature changes. The total impact of a supersonic fleet on radiative forcing (mainly water vapour) is reproduced within 5%. For subsonic air traffic (sustained emissions after 2050) results show that although ozone-radiative forcing is much less important than that from CO2 for the year 2100. However the impact on temperature is of comparable size even when taking into account temperature decreases from CH4. That implies that all future measures for climate stabilisation should concentrate on both CO2 and NOx emissions. A direct comparison of super- with subsonic aircraft (250 passengers, 5400 nm) reveals a 5 times higher climate impact of supersonics.

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Climate impact of volcanic eruptions: the sensitivity to eruption season and latitude in MPI-ESM ensemble experiments

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-13425-2021 ◽

2021 ◽

Vol 21 (17) ◽

pp. 13425-13442

Author(s):

Zhihong Zhuo ◽

Ingo Kirchner ◽

Stephan Pfahl ◽

Ulrich Cubasch

Keyword(s):

Southern Hemisphere ◽

Regional Climate ◽

Volcanic Eruptions ◽

Climate Impact ◽

Climate Impacts ◽

Cloud Formation ◽

Radiative Effects ◽

Near Surface ◽

Volcanic Aerosols ◽

The Impact

Abstract. Explosive volcanic eruptions influence near-surface temperature and precipitation especially in the monsoon regions, but the impact varies with different eruption seasons and latitudes. To study this variability, two groups of ensemble simulations are performed with volcanic eruptions in June and December at 0∘ representing an equatorial eruption (EQ) and at 30∘ N and 30∘ S representing Northern and Southern Hemisphere eruptions (NH and SH). Results show significant cooling especially in areas with enhanced volcanic aerosol content. Compared to the EQ eruption, stronger cooling emerges in the Northern Hemisphere after the NH eruption and in the Southern Hemisphere after the SH eruption. Stronger precipitation variations occur in the tropics than in the high latitudes. Summer and winter eruptions lead to similar hydrological impacts. The NH and the SH eruptions have reversed climate impacts, especially in the regions of the South Asian summer monsoon (SASM). After the NH eruption, direct radiative effects of volcanic aerosols induce changes in the interhemispheric and land–sea thermal contrasts, which move the intertropical convergence zone (ITCZ) southward and weaken the SASM. This reduces the moisture transport from the ocean and reduces cloud formation and precipitation in India. The subsequent radiative feedbacks due to regional cloud cover lead to warming in India. After the SH eruption, vice versa, a northward movement of the ITCZ and strengthening of the SASM, along with enhanced cloud formation, lead to enhanced precipitation and cooling in India. This emphasizes the sensitivity of regional climate impacts of volcanic eruptions to eruption latitude, which relates to the dynamical response of the climate system to radiative effects of volcanic aerosols and the subsequent regional physical feedbacks. Our results indicate the importance of considering dynamical and physical feedbacks to understand the mechanism behind regional climate responses to volcanic eruptions and may also shed light on the climate impact and potential mechanisms of stratospheric aerosol engineering.

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Climate Impact Mitigation Potential of Formation Flight

Aerospace ◽

10.3390/aerospace8010014 ◽

2021 ◽

Vol 8 (1) ◽

pp. 14

Author(s):

Tobias Marks ◽

Katrin Dahlmann ◽

Volker Grewe ◽

Volker Gollnick ◽

Florian Linke ◽

...

Keyword(s):

Climate Model ◽

Temperature Response ◽

Cost Savings ◽

Interdisciplinary Approach ◽

Climate Impact ◽

Formation Flight ◽

Surface Temperature Change ◽

Near Surface ◽

Mitigation Potential ◽

Saturation Effects

The aerodynamic formation flight, which is also known as aircraft wake-surfing for efficiency (AWSE), enables aircraft to harvest the energy inherent in another aircraft’s wake vortex. As the thrust of the trailing aircraft can be reduced during cruise flight, the resulting benefit can be traded for longer flight time, larger range, less fuel consumption, or cost savings accordingly. Furthermore, as the amount and location of the emissions caused by the formation are subject to change and saturation effects in the cumulated wake of the formation can occur, AWSE can favorably affect the climate impact of the corresponding flights. In order to quantify these effects, we present an interdisciplinary approach combining the fields of aerodynamics, aircraft operations and atmospheric physics. The approach comprises an integrated model chain to assess the climate impact for a given air traffic scenario based on flight plan data, aerodynamic interactions between the formation members, detailed trajectory calculations as well as on an adapted climate model accounting for the saturation effects resulting from the proximity of the emissions of the formation members. Based on this approach, we derived representative AWSE scenarios for the world’s major airports by analyzing and assessing flight plans. The resulting formations were recalculated by a trajectory calculation tool and emission inventories for the scenarios were created. Based on these inventories, we quantitatively estimated the climate impact using the average temperature response (ATR) as climate metric, calculated as an average global near surface temperature change over a time horizon of 50 years. It is shown, that AWSE as a new operational procedure has a significant mitigation potential on climate impact. For a global formation flight scenario, we estimated the average relative change of climate response to range between 22% and 24% while the relative fuel saving effects sum up to 5–6%.

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AirClim: an efficient tool for climate evaluation of aircraft technology

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-4621-2008 ◽

2008 ◽

Vol 8 (16) ◽

pp. 4621-4639 ◽

Cited By ~ 60

Author(s):

V. Grewe ◽

A. Stenke

Keyword(s):

Climate Change ◽

Water Vapour ◽

Radiative Forcing ◽

Climate Impacts ◽

Assessment Tools ◽

Surface Temperature Change ◽

Near Surface ◽

Temperature Changes ◽

Wide Range ◽

Concentration Changes

Abstract. Climate change is a challenge to society and to cope with requires assessment tools which are suitable to evaluate new technology options with respect to their impact on global climate. Here we present AirClim, a model which comprises a linearisation of atmospheric processes from the emission to radiative forcing, resulting in an estimate in near surface temperature change, which is presumed to be a reasonable indicator for climate change. The model is designed to be applicable to aircraft technology, i.e. the climate agents CO2, H2O, CH4 and O3 (latter two resulting from NOx-emissions) and contrails are taken into account. AirClim combines a number of precalculated atmospheric data with aircraft emission data to obtain the temporal evolution of atmospheric concentration changes, radiative forcing and temperature changes. These precalculated data are derived from 25 steady-state simulations for the year 2050 with the climate-chemistry model E39/C, prescribing normalised emissions of nitrogen oxides and water vapour at various atmospheric regions. The results show that strongest climate impacts (year 2100) from ozone changes occur for emissions in the tropical upper troposphere (60 mW/m2; 80 mK for 1 TgN/year emitted) and from methane changes from emissions in the middle tropical troposphere (−2.7% change in methane lifetime; –30 mK per TgN/year). For short-lived species (e.g. ozone, water vapour, methane) individual perturbation lifetimes are derived depending on the region of emission. A comparison of this linearisation approach with results from a comprehensive climate-chemistry model shows reasonable agreement with respect to concentration changes, radiative forcing, and temperature changes. For example, the total impact of a supersonic fleet on radiative forcing (mainly water vapour) is reproduced within 10%. A wide range of application is demonstrated.

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Modeling the present and future impact of aviation on climate: an AOGCM approach with online coupled chemistry

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-10027-2013 ◽

2013 ◽

Vol 13 (19) ◽

pp. 10027-10048 ◽

Cited By ~ 13

Author(s):

P. Huszar ◽

H. Teyssèdre ◽

M. Michou ◽

A. Voldoire ◽

D. J. L. Olivié ◽

...

Keyword(s):

Co2 Emissions ◽

General Circulation ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Climate Impacts ◽

Ozone Production ◽

The Arctic ◽

Near Surface ◽

Aviation Emissions ◽

The Impact

Abstract. Our work is among the first that use an atmosphere-ocean general circulation model (AOGCM) with online chemistry to evaluate the impact of future aviation emissions on temperature. Other particularities of our study include non-scaling to the aviation emissions, and the analysis of models' transient response using ensemble simulations. The model we use is the Météo-France CNRM-CM5.1 earth system model extended with the REPROBUS chemistry scheme. The time horizon of our interest is 1940–2100, assuming the A1B SRES scenario. We investigate the present and future impact of aviation emissions of CO2, NOx and H2O on climate, taking into account changes in greenhouse gases, contrails and contrail-induced cirrus (CIC). As in many transport-related impact studies, we distinguish between the climate impacts of CO2 emissions and those of non-CO2 emissions. Aviation-produced aerosol is not considered in the study. Our modeling system simulated a notable sea-ice bias in the Arctic, and therefore results concerning the surface should be viewed with caution. The global averaged near-surface CO2 impact reaches around 0.1 K by the end of the 21st century, while the non-CO2 impact reaches 0.2 K in the second half of the century. The NOx emissions impact is almost negligible in our simulations, as our aviation-induced ozone production is small. As a consequence, the non-CO2 signal is very similar to the CIC signal. The seasonal analysis shows that the strongest warming due to aviation is modeled for the late summer and early autumn. In the stratosphere, a significant cooling is attributed to aviation CO2 emissions (−0.25 K by 2100). A −0.3 K temperature decrease is modeled when considering all the aviation emissions, but no significant signal appears from the CIC or NOx forcings in the stratosphere.

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The Climate Impact of COVID19 Induced Contrail Changes

10.5194/acp-2021-210 ◽

2021 ◽

Author(s):

Andrew Gettelman ◽

Chieh-Chieh Chen ◽

Charles G. Bardeen

Keyword(s):

Surface Temperature ◽

Land Surface ◽

Radiative Forcing ◽

Climate Impact ◽

Climate Impacts ◽

Infrared Heating ◽

Boreal Summer ◽

Surface Temperature Change ◽

Effective Radiative Forcing ◽

Standard Deviations

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

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Climate impact of volcanic eruptions: the sensitivity to eruption season and latitude in MPI-ESM ensemble experiments

10.5194/acp-2021-260 ◽

2021 ◽

Author(s):

Zhihong Zhuo ◽

Ingo Kirchner ◽

Stephan Pfahl ◽

Ulrich Cubasch

Keyword(s):

Southern Hemisphere ◽

South Asian ◽

Volcanic Eruptions ◽

Climate Impacts ◽

South Asian Summer Monsoon ◽

The South ◽

Radiative Effects ◽

Near Surface ◽

Volcanic Aerosols ◽

The Impact

Abstract. Explosive volcanic eruptions influence near-surface temperature and precipitation especially in the monsoon regions, but the impact varies with different eruption seasons and latitudes. To study this variability, two groups of ensemble simulations are performed with volcanic eruptions in June and December at 0° representing an equatorial eruption (EQ) and at 30° N and 30° S representing northern and southern hemisphere eruptions (NH and SH). Results show significant cooling especially in areas with enhanced volcanic aerosol content. Stronger cooling emerges in the northern (southern) hemisphere after the NH (SH) eruption compared to the EQ eruption. Stronger precipitation variations occur in the tropics than in the high latitudes. Summer and winter eruptions lead to similar climate impacts. The NH and the SH eruptions have reversed climate impacts, especially in the South Asian monsoon regions. After the NH (SH) eruption, direct radiative effects of volcanic aerosols induce changes in the interhemispheric and land-sea thermal contrasts, which move the intertropical convergence zone southward (northward) and weaken (strengthen) the South Asian summer monsoon. This reduces (increases) the moisture transport from the ocean to India, and reduces (enhances) cloud formation. The subsequent radiative feedbacks due to regional cloud cover lead to warming (cooling) in India. This emphasis the sensitivity of regional climate impacts of volcanic eruptions to eruption latitude, which relates to the dynamical response of the climate system to radiative effects of volcanic aerosols and the subsequent regional physical feedbacks.

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Multi-model climate impact assessment and intercomparison for three large-scale river basins on three continents

Earth System Dynamics Discussions ◽

10.5194/esdd-5-849-2014 ◽

2014 ◽

Vol 5 (2) ◽

pp. 849-900 ◽

Cited By ~ 5

Author(s):

T. Vetter ◽

S. Huang ◽

V. Aich ◽

T. Yang ◽

X. Wang ◽

...

Keyword(s):

Impact Assessment ◽

Climate Models ◽

Water Discharge ◽

River Basins ◽

Climate Impact ◽

Climate Impacts ◽

Hydrological Models ◽

Climate Scenarios ◽

Climate Impact Assessment ◽

The Impact

Abstract. Climate change impacts on hydrological processes should be simulated for river basins using validated models and multiple climate scenarios in order to provide reliable results for stakeholders. In the last 10–15 years climate impact assessment was performed for many river basins worldwide using different climate scenarios and models. Nevertheless, the results are hardly comparable and do not allow to create a full picture of impacts and uncertainties. Therefore, a systematic intercomparison of impacts is suggested, which should be done for representative regions using state-of-the-art models. Our study is intended as a step in this direction. The impact assessment presented here was performed for three river basins on three continents: Rhine in Europe, Upper Niger in Africa and Upper Yellow in Asia. For that, climate scenarios from five GCMs and three hydrological models: HBV, SWIM and VIC, were used. Four "Representative Concentration Pathways" (RCPs) covering a range of emissions and land-use change projections were included. The objectives were to analyze and compare climate impacts on future trends considering three runoff quantiles: Q90, Q50 and Q10 and on seasonal water discharge, and to evaluate uncertainties from different sources. The results allow drawing some robust conclusions, but uncertainties are large and shared differently between sources in the studied basins. The robust results in terms of trend direction and slope and changes in seasonal dynamics could be found for the Rhine basin regardless which hydrological model or forcing GCM is used. For the Niger River scenarios from climate models are the largest uncertainty source, providing large discrepancies in precipitation, and therefore clear projections are difficult to do. For the Upper Yellow basin, both the hydrological models and climate models contribute to uncertainty in the impacts, though an increase in high flows in future is a robust outcome assured by all three hydrological models.

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Climate functions for the use in multi-disciplinary optimisation in the pre-design of supersonic business jet

The Aeronautical Journal ◽

10.1017/s0001924000003705 ◽

2010 ◽

Vol 114 (1154) ◽

pp. 259-269 ◽

Cited By ~ 2

Author(s):

V. Grewe ◽

A. Stenke ◽

M. Plohr ◽

V. D. Korovkin

Keyword(s):

Carbon Dioxide ◽

Water Vapour ◽

Aircraft Engine ◽

Climate Impact ◽

Near Surface ◽

Supersonic Aircraft ◽

Fuel Flow ◽

Business Jet ◽

Eu Project ◽

The Impact

Abstract Mitigation of climate change is a challenge to science and society. Here, we establish a methodology, applicable in multi-disciplinary optimisation (MDO) during aircraft pre-design, allowing a minimisation of the aircraft’s potential climate impact. In this first step we consider supersonic aircraft flying at a cruise altitude between 45kfeet (~13·5km, 150hPa) and 67kfeet (~20·5km, 50hPa). The methodology is based on climate functions, which give a relationship between 4 parameters representing an aircraft/engine configuration and an expected impact on global mean near surface temperature as an indicator for the impact on climate via changes in the greenhouse gases carbon dioxide, water vapour, ozone and methane. These input parameters are cruise altitude pressure, fuel consumption, fuel flow and Mach number. The climate functions for water vapour and carbon dioxide are independent from the chosen engine, whereas the climate functions for ozone and methane depend on engine parameters describing the nitrogen oxide emissions. Ten engine configurations are taken into account, which were considered in the framework of the EU-project HISAC. An analysis of the reliability of the climate functions with respect to the simplified climate-chemistry model AirClim and a detailed analysis of the climate functions is given.

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ATTRICI v1.1 – counterfactual climate for impact attribution

Geoscientific Model Development ◽

10.5194/gmd-14-5269-2021 ◽

2021 ◽

Vol 14 (8) ◽

pp. 5269-5284

Author(s):

Matthias Mengel ◽

Simon Treu ◽

Stefan Lange ◽

Katja Frieler

Keyword(s):

Climate Change ◽

Climate Impact ◽

Climate Impacts ◽

General Definition ◽

Impact Model ◽

Climate Data ◽

Climate Trends ◽

Long Term Changes ◽

The Impact

Abstract. Attribution in its general definition aims to quantify drivers of change in a system. According to IPCC Working Group II (WGII) a change in a natural, human or managed system is attributed to climate change by quantifying the difference between the observed state of the system and a counterfactual baseline that characterizes the system's behavior in the absence of climate change, where “climate change refers to any long-term trend in climate, irrespective of its cause” (IPCC, 2014). Impact attribution following this definition remains a challenge because the counterfactual baseline, which characterizes the system behavior in the hypothetical absence of climate change, cannot be observed. Process-based and empirical impact models can fill this gap as they allow us to simulate the counterfactual climate impact baseline. In those simulations, the models are forced by observed direct (human) drivers such as land use changes, changes in water or agricultural management but a counterfactual climate without long-term changes. We here present ATTRICI (ATTRIbuting Climate Impacts), an approach to construct the required counterfactual stationary climate data from observational (factual) climate data. Our method identifies the long-term shifts in the considered daily climate variables that are correlated to global mean temperature change assuming a smooth annual cycle of the associated scaling coefficients for each day of the year. The produced counterfactual climate datasets are used as forcing data within the impact attribution setup of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP3a). Our method preserves the internal variability of the observed data in the sense that factual and counterfactual data for a given day have the same rank in their respective statistical distributions. The associated impact model simulations allow for quantifying the contribution of climate change to observed long-term changes in impact indicators and for quantifying the contribution of the observed trend in climate to the magnitude of individual impact events. Attribution of climate impacts to anthropogenic forcing would need an additional step separating anthropogenic climate forcing from other sources of climate trends, which is not covered by our method.

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