TransClim (v1.0): a chemistry–climate response model for assessing the effect of mitigation strategies for road traffic on ozone

Road traffic emits not only carbon dioxide (CO2) and particulate matter, but also other pollutants such as nitrogen oxides (NOx), volatile organic compounds (VOCs) and carbon monoxide (CO). These chemical species influence the atmospheric chemistry and produce ozone (O3) in the troposphere. Ozone acts as a greenhouse gas and thus contributes to anthropogenic global warming. Technological trends and political decisions can help to reduce the O3 effect of road traffic emissions on climate. In order to assess the O3 response of such mitigation options on climate, we developed a chemistry–climate response model called TransClim (Modelling the effect of surface Transportation on Climate). The current version considers road traffic emissions of NOx, VOC and CO and determines the O3 change and its corresponding stratosphere-adjusted radiative forcing. Using a tagging method, TransClim is further able to quantify the contribution of road traffic emissions to the O3 concentration. Thus, TransClim determines the contribution to O3 as well as the change in total tropospheric O3 of a road traffic emission scenario. Both quantities are essential when assessing mitigation strategies. The response model is based on lookup tables which are generated by a set of emission variation simulations performed with the global chemistry–climate model EMAC (ECHAM5 v5.3.02, MESSy v2.53.0). Evaluating TransClim against independent EMAC simulations reveals low deviations of all considered species (0.01 %–10 %). Hence, TransClim is able to reproduce the results of an EMAC simulation very well. Moreover, TransClim is about 6000 times faster in computing the climate effect of an emission scenario than the complex chemistry–climate model. This makes TransClim a suitable tool to efficiently assess the climate effect of a broad range of mitigation options for road traffic or to analyse uncertainty ranges by employing Monte Carlo simulations

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

Comparison of the O3 chemistry in the Po Valley with that in the Benelux region as simulated with MECO(n)

This study investigates the contributions of anthropogenic non-traffic (i.e. households, industry, etc.) and land transport emis- sions to the ozone budget in Europe and Southeast Asia. For this we performed two simulations with the global/regional che- mistry-climate model MECO(n) including a source apportionment method for ozone to investigate regional differences bet- ween the chemical regimes, especially of the ozone formation potential. Our findings show that contributions from global anthropogenic non-traffic emissions to ground-level ozone are larger in Southeast Asia than in Europe. The contrary applies for the global land transport emissions, which are more important in Europe compared to Southeast Asia

Comparison of the O3 chemistry in the Po Valley with that in the Benelux region as simulated with MECO(n)

Non-traffic (i.e. households, industry, etc.) emissions and land transport emissions are important anthropogenic precursors of tropospheric O3 and affect the air quality and contribute to global climate change. In order to improve air quality and mitigate climate change, robust knowledge of the amount of O3 formed by different emission sources is required. This study investigates the contributions of the different emission sectors to the ground-level ozone budget in Europe and Southeast Asia. For the present study we applied the MECO(n) model system, which couples the global chemistry-climate model EMAC on-line with the regional chemistry-climate model COSMO-CLM/MESSy. We used MECO(n) with a source apportionment method for ozone to investigate regional differences of the contributions from different emissions to ground-level ozone. Our findings show that contributions from anthropogenic non-traffic emissions to ground-level ozone are larger in Southeast Asia than in Europe. The contrary applies for the land transport emissions, which are more important in Europe compared to Southeast Asia

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

Feasibility of climate-optimized air traffic routing for trans-Atlantic flights

Current air traffic routing is motivated by minimizing economic costs, such as fuel use. In addition to the climate impact of CO2 emissions from this fuel use, aviation contributes to climate change through non-CO2 impacts, such as changes in atmospheric ozone and methane concentrations and formation of contrail-cirrus. These non-CO2 impacts depend significantly on where and when the aviation emissions occur. The climate impact of aviation could be reduced if flights were routed to avoid regions where emissions have the largest impact. Here, we present the first results where a climate-optimized routing strategy is simulated for all trans-Atlantic flights on 5 winter and 3 summer days, which are typical of representative winter and summer North Atlantic weather patterns. The optimization separately considers eastbound and westbound flights, and accounts for the effects of wind on the flight routes, and takes safety aspects into account. For all days considered, we find multiple feasible combinations of flight routes which have a smaller overall climate impact than the scenario which minimizes economic cost. We find that even small changes in routing, which increase the operating costs (mainly fuel) by only 1% lead to considerable reductions in climate impact of 10%. This cost increase could be compensated by market-based measures, if costs for non-CO2 climate impacts were included. Our methodology is a starting point for climate-optimized flight planning, which could also be applied globally. Although there are challenges to implementing such a system, we present a road map with the steps to overcome these