TY - JOUR A1 - Macdonald, Elena A1 - Otero, Noelia A1 - Butler, Tim T1 - A comparison of long-term trends in observations and emission inventories of NOx JF - Atmospheric chemistry and physics / European Geosciences Union N2 - Air pollution is a pressing issue that is associated with adverse effects on human health, ecosystems, and climate. Despite many years of effort to improve air quality, nitrogen dioxide (NO2) limit values are still regularly exceeded in Europe, particularly in cities and along streets. This study explores how concentrations of nitrogen oxides (NOx = NO + NO2) in European urban areas have changed over the last decades and how this relates to changes in emissions. To do so, the incremental approach was used, comparing urban increments (i.e. urban background minus rural concentrations) to total emissions, and roadside increments (i.e. urban roadside concentrations minus urban background concentrations) to traffic emissions. In total, nine European cities were assessed. The study revealed that potentially confounding factors like the impact of urban pollution at rural monitoring sites through atmospheric transport are generally negligible for NOx. The approach proves therefore particularly useful for this pollutant. The estimated urban increments all showed downward trends, and for the majority of the cities the trends aligned well with the total emissions. However, it was found that factors like a very densely populated surrounding or local emission sources in the rural area such as shipping traffic on inland waterways restrict the application of the approach for some cities. The roadside increments showed an overall very diverse picture in their absolute values and trends and also in their relation to traffic emissions. This variability and the discrepancies between roadside increments and emissions could be attributed to a combination of local influencing factors at the street level and different aspects introducing inaccuracies to the trends of the emis-sion inventories used, including deficient emission factors. Applying the incremental approach was evaluated as useful for long-term pan-European studies, but at the same time it was found to be restricted to certain regions and cities due to data availability issues. The results also highlight that using emission inventories for the prediction of future health impacts and compliance with limit values needs to consider the distinct variability in the concentrations not only across but also within cities. Y1 - 2021 U6 - https://doi.org/10.5194/acp-21-4007-2021 SN - 1680-7316 SN - 1680-7324 VL - 21 IS - 5 SP - 4007 EP - 4023 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Mar, Kathleen A. A1 - Unger, Charlotte A1 - Walderdorff, Ludmila A1 - Butler, Tim T1 - Beyond CO2 equivalence BT - The impacts of methane on climate, ecosystems, and health JF - Environmental science & policy N2 - In this article we review the physical and chemical properties of methane (CH4) relevant to impacts on climate, ecosystems, and air pollution, and examine the extent to which this is reflected in climate and air pollution governance. Although CH4 is governed under the UNFCCC climate regime, its treatment there is limited to the ways in which it acts as a "CO2 equivalent" climate forcer on a 100-year time frame. The UNFCCC framework neglects the impacts that CH4 has on near-term climate, as well its impacts on human health and ecosystems, which are primarily mediated by methane's role as a precursor to tropospheric ozone. Frameworks for air quality governance generally address tropospheric ozone as a pollutant, but do not regulate CH4 itself. Methane's climate and air quality impacts, together with its alarming rise in atmospheric concentrations in recent years, make it clear that mitigation of CH4 emissions needs to be accelerated globally. We examine challenges and opportunities for further progress on CH4 mitigation within the international governance landscapes for climate change and air pollution. KW - Methane KW - Climate governance KW - Air pollution KW - International policy KW - Short-lived climate pollutants KW - Global warming potential Y1 - 2022 U6 - https://doi.org/10.1016/j.envsci.2022.03.027 SN - 1462-9011 SN - 1873-6416 VL - 134 SP - 127 EP - 136 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Schneidemesser, Erika von A1 - Sibiya, Bheki A1 - Caseiro, Alexandre A1 - Butler, Tim A1 - Lawrence, Mark A1 - Leitao, Joana A1 - Lupaşcu, Aura A1 - Salvador, Pedro T1 - Learning from the COVID-19 lockdown in Berlin BT - Observations and modelling to support understanding policies to reduce NO2 JF - Atmospheric environment: X N2 - Urban air pollution is a substantial threat to human health. Traffic emissions remain a large contributor to air pollution in urban areas. The mobility restrictions put in place in response to the COVID-19 pandemic provided a large-scale real-world experiment that allows for the evaluation of changes in traffic emissions and the corresponding changes in air quality. Here we use observational data, as well as modelling, to analyse changes in nitrogen dioxide, ozone, and particulate matter resulting from the COVID-19 restrictions at the height of the lockdown period in Spring of 2020. Accounting for the influence of meteorology on air quality, we found that reduction of ca. 30-50 % in traffic counts, dominated by changes in passenger cars, corresponded to reductions in median observed nitrogen dioxide concentrations of ca. 40 % (traffic and urban background locations) and a ca. 22 % increase in ozone (urban background locations) during weekdays. Lesser reductions in nitrogen dioxide concentrations were observed at urban background stations at weekends, and no change in ozone was observed. The modelled reductions in median nitrogen dioxide at urban background locations were smaller than the observed reductions and the change was not significant. The model results showed no significant change in ozone on weekdays or weekends. The lack of a simulated weekday/weekend effect is consistent with previous work suggesting that NOx emissions from traffic could be significantly underestimated in European cities by models. These results indicate the potential for improvements in air quality due to policies for reducing traffic, along with the scale of reductions that would be needed to result in meaningful changes in air quality if a transition to sustainable mobility is to be seriously considered. They also confirm once more the highly relevant role of traffic for air quality in urban areas. KW - Urban areas KW - Air pollution KW - Emissions KW - COVID-19 KW - Nitrogen dioxide KW - Ozone KW - Europe Y1 - 2021 U6 - https://doi.org/10.1016/j.aeaoa.2021.100122 SN - 2590-1621 VL - 12 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Weger, Lindsey B. A1 - Lupaşcu, Aura A1 - Cremonese, Lorenzo A1 - Butler, Tim T1 - Modeling the impact of a potential shale gas industry in Germany and the United Kingdom on ozone with WRF-Chem JF - Elementa-sccience of the anthropocene N2 - Germany and the United Kingdom have domestic shale gas reserves which they may exploit in the future to complement their national energy strategies. However gas production releases volatile organic compounds (VOC) and nitrogen oxides (NOx), which through photochemical reaction form ground-level ozone, an air pollutant that can trigger adverse health effects e.g. on the respiratory system. This study explores the range of impacts of a potential shale gas industry in these two countries on local and regional ambient ozone. To this end, comprehensive emission scenarios are used as the basis for input to an online-coupled regional chemistry transport model (WRF-Chem). Here we simulate shale gas scenarios over summer (June, July, August) 2011, exploring the effects of varying VOC emissions, gas speciation, and concentration of NOx emissions over space and time, on ozone formation. An evaluation of the model setup is performed, which exhibited the model’s ability to predict surface meteorological and chemical variables well compared with observations, and consistent with other studies. When different shale gas scenarios were employed, the results show a peak increase in maximum daily 8-hour average ozone from 3.7 to 28.3 μg m–3. In addition, we find that shale gas emissions can force ozone exceedances at a considerable percentage of regulatory measurement stations locally (up to 21% in Germany and 35% in the United Kingdom) and in distant countries through long-range transport, and increase the cumulative health-related metric SOMO35 (maximum percent increase of ~28%) throughout the region. Findings indicate that VOC emissions are important for ozone enhancement, and to a lesser extent NOx, meaning that VOC regulation for a future European shale gas industry will be of especial importance to mitigate unfavorable health outcomes. Overall our findings demonstrate that shale gas production in Europe can worsen ozone air quality on both the local and regional scales. KW - Shale gas KW - WRF-Chem KW - European air quality KW - Ozone KW - Methane leakage KW - Emission scenarios Y1 - 2019 U6 - https://doi.org/10.1525/elementa.387 SN - 2325-1026 VL - 7 PB - Univ California Press CY - Oakland ER -