the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Jan 2026
From Continental to Street Scales: Climate Change Impacts on Atmospheric Composition over Europe and London
Abstract. Climate change will impact ozone (O3) and fine particulate matter (PM2.5) through its influence on natural emissions, atmospheric chemistry, deposition and transport. A coupled modelling approach is employed to identify the key processes and determine how regional air pollution across Europe and urban-scale air quality in London in the 2090s are impacted by climate change under Representative Concentration Pathway (RCP)8.5. Climate change projections from the HadGEM2-ES Earth System Model nudge the nested WRF-EMEP4UK model, which drives the street-scale ADMS-Urban model. Annual-mean temperature increases exceeding 4 °C produce substantial increases in summer biogenic isoprene emissions. There is a strong contrast in summer and winter-mean O3 responses to climate change, with large summer increases over southern Europe (≤ 10 ppbv) and winter decreases over Europe. Annual-average PM2.5 concentrations are elevated (5–10 µgm-3) over most of Europe, also driven by higher isoprene emissions that promote secondary organic aerosol formation. Decreases in primary and inorganic PM2.5 components are prominent in winter. The seasonality of urban air pollution is modified over London under climate change: the O3 peak amplitude is reduced, whilst the winter peaks in PM2.5 and NO2 are more pronounced, with nighttime increases. The diurnal profile of urban air pollution typically flattens. Climate-induced changes in O3 aid attainment of long-term air quality guidelines in northern Europe, but pose challenges elsewhere. Achieving long-term PM2.5 guidelines over much of Europe becomes increasing difficult with climate change, while attaining short-term air quality guidelines in London remains a major challenge, especially for NO2.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: open (until 23 Feb 2026)
- RC1: 'Comment on egusphere-2025-6407', Anonymous Referee #1, 02 Feb 2026 reply
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- 1
This study evaluates climate-induced air-quality changes at regional scale across Europe and at urban scale for London in the 2090s under the RCP8.5 scenario, using a nested global–regional–urban modelling framework that links HadGEM2-ES, WRF–EMEP4UK, and ADMS-Urban. The paper presents detailed results for ozone and PM2.5, including differences between northern and southern Europe, summer vs. winter patterns, diurnal changes, and the main processes driving these responses. It also discusses what the results mean for meeting WHO air-quality guidelines.
Overall, the work is carefully designed, clearly written, and provides a thorough and policy-relevant assessment of climate-AQ interactions at regional (Europe) and urban (London) scales. The introduction provides a solid review of existing literature, and the methodology is meticulously designed. The results are rich in detail but still stay logically organized, and the discussion is thoughtful. I think this will be a valuable read for anyone working on climate-AQ interactions in Europe, and I support publication in ACP.
One suggestion, mainly to make the paper more interesting for readers outside Europe, is to more clearly state what the global-regional-urban setup adds compared to the more common global-regional approach. The authors mention this in a few places (e.g., around lines 675-679), but it is a bit spread out. My takeaway is that adding the urban model does not really change the main regional conclusions, but it does show much stronger spatial differences within the city. I think the paper would benefit from a more in-depth, focused paragraph that clearly says what changes (and what does not) when the urban model is included, and when this extra nesting is most worth doing in future studies.
A related point, which the authors may choose to address or not, is how to place the results in the context of uncertainty in future climate projections (internal variability and differences across climate models). As the authors note, this kind of nested setup makes it hard to run large ensembles. In some cases, uncertainty from using one climate projection could be larger than the added benefit of going to finer scale, depending on the question and metric. I do not see this as a weakness of the paper. Urban-scale projections are rare, and even uncertain estimates are better than none, especially for policy use. Still, a brief note acknowledging this trade-off, and saying how the authors view the robustness of the main takeaways, could strengthen the paper.
Finally, one small item: in line 330, the reference to “Fig. 1c” seems like it should be “Fig. S1c” (please check and fix if needed).