Globale Auswirkung des Straßenverkehrs auf die chemische Zusammensetzung der Atmosphäre

Road traffic represents one of the main sources of emissions to the atmosphere. This work determines the impact of road traffic emissions on the chemical composition of the atmosphere by a numerical modelling study with ECHAM4/CBM-IV. For the first time, global impact of non-methane-hydrocarbon-emissions (NMHCs) from road traffic is presented. Annual, global emissions from road traffic following a consumption-based approach amount to (8.8 +/- 1.8) Tg [N] nitrogen oxides, (206 +/- 86) Tg [CO] carbonmonoxide, and (34.4 +/- 18.9) Tg NMHCs. Road traffic emissions cause an increase of ozone, which is an important trace gas for the oxidizing capacity and the radiative budget of the atmosphere. In industrialized regions of the northern hemisphere the increase exceeds more than 20%. In remote regions an increase of more than 10% is calculated. Tropical latitudes show a relative contribution of more than 6% due to road traffic up to 10km. NOx-emissions account for about 70% of this ozone increase. Further, road traffic increases and decreases the concentration of hydroxyl radicals (OH) depending on geographical region and season. This again affects the oxidizing capacity and the lifetime of methane. In summer, road traffic causes in northern extratropics a 3% increase of OH, and in winter a decrease of 10%. These changes in chemical composition cause an indirect radiative forcing to the atmosphere. Ozone increases due to road traffic emissions (NOx, CO, NMHCs) result in an annual and global mean radiative forcing of 0.058 W/m^2. The indirect forcing due to road traffic-induced changes in the lifetime of methane amounts to 0.006 W/m^2. This forcing is temporal and spatial inhomogeneous, and can even possess a positive sign (e.g. in spring). Results show that NMHC-emissions considerably contribute to the global impact of road traffic emissions.Der Straßenverkehr gehört zu den Hauptverursachern von Spurengasemissionen in die Atmosphäre. In der vorliegenden Arbeit wurde im Rahmen einer numerischen Studie mit ECHAM4/CBM-IV der Einfluss dieser Emissionen auf die chemische Zusammensetzung der Atmosphäre auf globaler Skala bestimmt. Hierbei wurde erstmals in einem hochaufgelösten globalen Modell die Wirkung der Nicht-Methan-Kohlenwasserstoff(NMHC)-Emissionen berücksichtigt. Die mit einem verbrauchsorientierten Ansatz berechneten Emissionen des Straßenverkehrs betragen im Jahr 1990 weltweit jährlich (8.8 +/- 1.8) Tg [N] Stickoxide, (206 +/- 86) Tg [CO] Kohlenmonoxide und die (34.4 +/- 18.9) Tg NMHC. Straßenverkehrsemissionen erhöhen auf globaler Skala die Konzentration des Spurengases Ozon, welches eine wichtige Rolle für Oxidationskapazität und Strahlungsbilanz der Atmosphäre spielt. In den Quellregionen der Nordhemisphäre wird die Konzentration von Ozon um mehr als 20% und auch in entlegenen Regionen um mehr als 10% erhöht; in den Tropen im Sommer bis in 10 Kilometer Höhe um mehr als 6%. NOx-Emissionen sind für etwa 70% der Ozonzunahme verantwortlich. Zusätzlich beeinflusst der Straßenverkehr die Konzentration des Hydroxylradikals (OH) und so wiederum die Oxidationskapazität der Atmosphäre mit relativen, positiven und negativen, Beiträgen von bis zu 10%. Im Sommer führt er in den nördlichen Extratropen zu einer OH-Zunahme um 3%, im Winter zu einer Abnahme um 10%. Diese Veränderung der Konzentration der chemischen Spezies (OH, O3) bewirkt einen indirekten Strahlungsantrieb auf die Atmosphäre. Die Ozonzunahme durch die Straßenverkehrsemissionen (NOx, CO, NMHCs) bewirkt im globalen Jahresmittel einen indirekten Strahlungsantrieb von 0.058 W/m^2. Die Veränderung im Hydroxylradikal ändert die Lebensdauer von Methan, wodurch sich ein indirekter Strahlungsantrieb von 0.006 W/m^2 (globales Jahresmittel) ergibt. Hierbei ist zu unterstreichen, dass dieser straßenverkehrsinduzierte Strahlungsantrieb zeitlich und räumlich inhomogen ist und sogar ein positives Vorzeichen besitzen kann (z.B. im Frühling). Die Studie zeigte, dass NMHC-Emissionen des Straßenverkehrs entscheidend zur Gesamtwirkung des Straßenverkehrs beitragen

ClimOP Project - Climate assessment of innovative mitigation strategies towards operational improvements in aviation

Air Transport has for a long time been linked to environmental issues like pollution, noise and climate change. The share of aviation amongst all anthropogenic emissions is about 3-5%. Considering the projected growth of air traffic for the next decades, aviations share of the total anthropogenic climate impact is expected to increase further. While CO2 emissions are the main focus in public discussions, non-CO2 emissions of aviation may have a similar impact on the climate as aviation's carbon dioxide, e.g. contrail cirrus, nitrogen oxides or aviation induced cloudiness. These non-CO2 effects are highly variable in their occurrence, with a strong spatially and temporally variation, while acting on short- and long-term atmospheric time horizons. Reducing these non-CO2 effects can be exploited to significantly reduce the overall climate impact of aviation by avoiding regions with high climate sensitivity. The ClimOP project, funded by the Horizon2020 programme, investigates which operational improvements do have a positive impact on climate, taking non-CO2 effects into account. Subsequently, the project will analyses and will propose harmonized mitigation strategies that foster the implementation of these operational improvements. Some of these operational improvements include optimization of flight network operations, climate-optimized flight planning or upgrades to the airport infrastructure. The final goal of ClimOP is to provide recommendations to steer the decision and policymaking in the European Union (EU) Aviation sector. To reach this goal, ClimOP employs a six-step methodology that focuses on stakeholders needs by using an iterative validation process. To this end, the ClimOp consortium builds on its knowledge and expertise covering the whole spectrum from aviation operations research as well as atmospheric science and consulting to airline and airport operations. The research work presented here focusing on further developments of methods used for identifying climate optimized flight trajectories. We investigate what physical processes are responsible for the climate impact of contrails, their spatial and temporal variation and explore how can such information be efficiently made available for operational climate mitigation options and trajectory optimizations. In order to study the physical processes resulting in the climate impact of contrails we use the global Earth System model system called Modular Earth Submodel System (MESSy) and the Earth-system model EMAC, which contains various submodels. This model is employed to calculate the atmospheric impact of standardized air traffic emissions at predefined latitudes, longitudes, altitudes and times. In this framework, numerical simulation on Lagrangian trajectory transportation are performed

Eco-efficient flight trajectories - Using a Lagrangian approach in EMAC to investigate contrail formation in the mid latitudes

Air transport has for a long time been linked to environmental issues like pollution, noise and climate change. While CO2 emissions are the main focus in public discussions, non-CO2 emissions of aviation may have a similar impact on the climate as aviation's carbon dioxide, e.g. contrail cirrus, nitrogen oxides or aviation induced cloudiness. While the effects of CO2 on climate are independent of location and situation during release, non-CO2 effects such as contrail formation vary depending on meteorological background. Previous studies investigated the influence of different weather situations on aviation’s climate change contribution, identifying climate sensitive regions and generating data products which enable air traffic management (ATM) to plan for climate optimized trajectories. The research presented here focuses on the further development of methods to determine the sensitivity of the atmosphere to aviation emissions with respect to climate effects in order to determine climate optimized aircraft trajectories. While previous studies focused on characterizing the North Atlantic Flight Corridor region, this study aims to extend the geographic scope by performing Lagrangian simulations in a global climate model EMAC for the northern hemispheric extratropical regions and tropical latitudes. This study addresses how realistically the physical conditions and processes for contrail formation and life cycle are represented in the upper troposphere and lower stratosphere by comparing them to airborne observations (HALO measurement campaign, CARIBIC/IAGOS scheduled flight measurements), examining key variables such as temperature or humidity. Direct comparison of model data with observations using clusters of data provides insight into the extent to which systematic biases exist that are relevant to the climate effects of contrails. We perform this comparison for different vertical resolutions to assess which vertical resolution in the EMAC model is well suited for studying contrail formation. Together with this model evaluation using aircraft measurements, the overall concept for studying the life cycle of contrails in the modular global climate model EMAC is introduced. Hereby, the concept for the development of a MET service that can be provided to ATM to evaluate contrail formation and its impact on the climate along planned aircraft trajectories is presented. Within the ClimOP collaborative project, we can investigate which physical processes determine the effects of contrails on climate and study their spatial and temporal variation. In addition, these climate change functions enable case studies that assess the impact of contrails on climate along trajectories and use alternative trajectories that avoid these regions of the atmosphere that have the potential to form contrails with a large radiative effect. This study is part of the ClimOP project and has received funding from European Union’s Horizo

Climate assessment of single flights: Deduction of route specific equivalent CO2 emissions

Climate impact of anthropogenic activities is more and more of public concern. But while CO2 emissions are accounted in emissions trading and mitigation plans, emissions of non-CO2 components contributing to climate change receive much less attention. One of the anthropogenic emission sectors, where non-CO2 effects play an important part, is aviation. Hence, for a quantitative estimate of total aviation climate impact, assessments need to comprise both CO2 and non-CO2 effects (e.g., water vapor, nitrogen dioxide, and contrails), instead of calculating and providing only CO2 impacts. However, while a calculation of CO2 effects relies directly on fuel consumption, for non-CO2 effects detailed information on aircraft trajectory, engine emissions, and ambient atmospheric conditions are required. As often such comprehensive information is not available for all aircraft movements, a simplified calculation method is required to calculate non-CO2 impacts. In our study, we introduce a simple calculation method which allows quantifying climate assessment relying on mission parameters, involving distance and geographic flight region. We present a systematic analysis of simulated climate impact from more than 1000 city pairs with an Airbus A330-200 aircraft depending on the flight distance and flight region to derive simplified but still realistic representation of the non-CO2 climate effects. These new formulas much better represent the climate impact of non-CO2 effects compared to a constant CO2 multiplier. The mean square error decrease from 1.18 for a constant factor down to 0.24 for distance dependent factors and can be reduced even further to 0.19 for a distance and latitude dependent factor

Towards an aviation weather forecast for green operations

Aviation contributes about 3.5% of the total anthropogenic global warming through both CO2 and non-CO2 effects. This problem is aggravated by the large growth rate of the aviation sector (>4% per year), which was only temporarily interrupted by the Covid-19 pandemic. It is evident that measures need to be taken to lessen the climate impact by aviation. CO2 has a very long residence time, such that its climate impact does not depend on when and where it is emitted. In contrast, non-CO2 emissions act on shorter time scales and their effect thus depends on the weather and synoptic situation at the time and location of the emission. This is particularly evident for contrails whose individual impacts range from strong cooling to strong warming, depending on the actual situation. It is thus possible to lessen the climate impact of aviation by planning flights such that climate-sensitive regions (i.e. regions where emissions would have a particularly strong warming impact) are avoided. To make such ideas real, new developments in aviation weather forecast are needed. One example is the implementation of so-called algorithmic climate change functions which provide measures of potential climate impact of emissions depending on actual weather variables (e.g. temperature and geopotential). The result can be provided in different ways, e.g. as costs, such that they can be used directly as additional cost-functions in flight routing. Another example is the prediction of persistent contrails in order to avoid them either tactically (by directives of air traffic control to pilots en-route) or strategically (as above, during flight routing). As one requirement for contrail persistence is ice supersaturation, this atmospheric state must be represented by the numerical weather prediction models, which is currently challenging. Another possibility is a probabilistic prediction of contrails using the standard weather variables. In this talk we will present how ideas from several projects for a better mitigation of contrails and other aviation non-CO2 effects on climate can be incorporated into aviation weather forecast models

COVID-19 induced lower-tropospheric ozone changes

The recent COVID-19 pandemic with its countermeasures, e.g., lock-downs, resulted in decreases in emissions of various trace gases. Here we investigate the changes of ozone over Europe associated with these emission reductions using a coupled global/regional chemistry climate model. We conducted and analysed a business as usual (BAU) and a sensitivity (COVID19) simulation. A source apportionment (tagging) technique allows us to make a sector-wise attribution of these changes, e.g. to natural and anthropogenic sectors such as land transport. Our simulation results show a decrease of ozone of 8% over Europe in May 2020 due to the emission reductions. The simulated reductions are in line with observed changes in ground level ozone. The source apportionment results show that this decrease is mainly due to the decreased ozone precursors from anthropogenic origin. Further, our results show that the ozone reduction is much smaller than the reduction of the total NOx emissions (around 20 %), mainly caused by an increased ozone production efficiency. This means that more ozone is produced for each emitted NOx molecule. Hence, more ozone is formed from natural emissions and the ozone productivities of the remaining anthropogenic emissions increase. Our results show that politically induced emissions reductions cannot simply be transferred to ozone reductions, which needs to be considered when designing mitigation strategies

FlyATM4E (SESAR ER) - Mitigating aviation climate impact by climate-optimized aircraft trajectories

Darstellung des Projekts FlyATM4

The CO2 and non-CO2 climate effects of individual flights: simplified estimation of CO2 equivalent emission factors

As aviation’s contribution to anthropogenic climate change is increasing, industry aims at reducing the aviation climate effect. However, the large contribution of non-CO2 effects to the total climate effect of aviation and their large variability for each individual flight inhibit finding appropriate guidance. Here, we present a method for the simplified calculation of CO2 equivalent emissions, expressed using the physical climate metrics ATR100 or AGWP100, from CO2 and non-CO2 effects for a given flight, exclusively based on the aircraft seat category as well as the origin and destination airports. The simplified calculation method estimates non-CO2 climate effects of air traffic as precisely as possible, without detailed information on the actual flight route, actual fuel burn, and current weather situation. For this purpose, we evaluate a global data set containing detailed flight trajectories, flight emissions, and climate responses, and derive a set of regression formulas for climate effects, which we call climate effect functions, as well as regression formulas for fuel consumption and NOx emissions. Compared to previous studies, this method is available for a larger number of aircraft types, including most commercial airliners with seat capacities starting from 101 passengers, and delivers more specific results through a clustering approach. The climate effects calculated using the climate effect functions derived in this study exhibit a mean absolute relative error of 15.0 % and a root mean square error of 1.24 nK with respect to results from the climate response model AirClim. The climate effect functions are designed for climate footprint assessments, but would not create an incentive in an emission trading system, for which detailed information on the current weather as well as the actual flight route and profile would be required

Flying Air Traffic Management for the benefit of environment and climate

FlyATM4E developed a concept to identify climate-optimized aircraft trajectories which enable a robust and eco-efficient reduction in aviations climate impact expanding on approved climate-assessment methods and optimization approaches. Applying state of the art climate impact quantification methods for aircraft emissions, robust climate-optimized flight planning in trajectory-based operations is investigated