The imperative for climate-neutral cities necessitates an understanding of current urban pathways towards sustainability. This study examines the actions and commitments of 362 cities that have expressed an ambition for climate neutrality by 2030. Based on the Expressions of Interest in the 100 Climate-Neutral and Smart Cities Mission, we profile the preparedness of cities in implementing climate change mitigation plans, engaging in relevant research and innovation projects, participating in climate-related initiatives, and earning recognition through awards. Methodologically, our analysis encompasses a diverse sample of urban environments, scrutinizing the thematic distribution of action plans, the extent of R&I project participation, and the nature of initiatives and awards. The study reveals that only 27 cities declared no relevant plans, with the majority reporting the maximum of 5 plans, indicating robust strategic groundwork. Additionally, 255 cities have reported engagement in European R&I projects, with Horizon 2020/Horizon Europe being the most prevalent framework. The Covenant of Mayors for Climate & Energy emerged as the dominant initiative among cities, with 217 occurrences, underscoring its contribution to building climate ambition. Furthermore, a significant 256 cities have been recognized through awards, signifying a competitive spirit and drive for excellence in climate leadership. Nonetheless, a subset of cities reveal limited past experience, emphasizing the need for tailored support in the journey towards ambitious climate targets. This study aids in identifying key frameworks to accelerate sustainable urban transformation, providing valuable insights for policymakers and stakeholders.

How to cite: Ulpiani, G. and Vetters, N.: Forging ambition for climate neutrality: a study of 362 cities, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-2, https://doi.org/10.5194/icuc12-2, 2025.

The advancement of high-resolution satellite remote sensing and computational techniques has significantly improved our ability to detect global urban land cover and its evolution over time and space. These technological breakthroughs have led to the creation of various global urban land cover datasets, which are essential for assessing climate risks and understanding urbanization patterns in both observational and modeling frameworks in an increasingly urban world. However, despite their importance, these datasets often exhibit substantial discrepancies due to differences in urban definitions, classification methodologies, and data sources. These inconsistencies can lead to varying estimates of the extent and rate of urban expansion, and how they covary with various evolving hazards, posing challenges for researchers and policymakers who rely on these datasets for climate and urban planning studies.

Through an analysis of widely used, current-generation datasets, we observe a significant increase in global urban land area, which nearly tripled between 1985 and 2015. However, there are large discrepancies in the estimates of urban land across datasets from local to regional to continental scales. Interestingly, the largest divergences are seen for the most recent years on inclusion of the newly released 10 m resolution products, partly due to their ability to better resolve urban facets. This rapid urban expansion has profound implications for climate systems, including localized urban warming, increasing urban flood risks, and changes in regional atmospheric patterns. We explore the dependence of some of these impacts of urbanization on the dataset chosen for select use cases and discuss the importance of these uncertainties for both modeling and observational estimates of urban climate and environmental risks. Our results demonstrate the importance of choosing application-appropriate datasets for examining specific aspects of historical, present, and future urbanization with potential implications for informing sustainable development, resource allocation, and quantifying urban climate impacts.

How to cite: Chakraborty, T. (., Venter, Z., Demuzere, M., Zhan, W., Gao, J., Zhao, L., and Qian, Y.: Disagreements in estimates of urban land from global maps: Implications for assessments of urban climate risks, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-391, https://doi.org/10.5194/icuc12-391, 2025.

Understanding interactions between urban environments and regional climate change is crucial for assessing the impacts of cities on the climate and vice versa. Regional Climate Models (RCMs) offer a promising tool to simulate these interactions over decades or even centuries. RCM developments have moved towards increasing grid resolutions down to kilometer scales, and therewith the city scale. However, a key question remains: How well do RCMs capture cities and their interactions with the regional climate?

The global Flagship Pilot Study “URBan environments and Regional Climate Change” (FPS URB-RCC), under the WCRP CORDEX initiative, offers insight into this question. Firstly, through analysing how RCMs depict urban climates across scales using existing global CORDEX-CORE (~25 km) and European convection-permitting (2–4 km) simulations. Secondly, through coordinated experiments the FPS assesses how different combinations of urban schemes and RCMs affect the results for the Paris region (France), encompassing over 30 simulations from 15+ modeling groups.

Key findings show that RCMs capture urban climate imprints, with higher-resolution simulations improving accuracy. Advanced urban schemes outperform simple bulk parameterizations, particularly for the nighttime urban heat island effect. Urban land-surface data quality is as crucial as parameterizations, yet RCMs globally underestimate urban land use, especially in Africa and Asia. Sensitivity experiments confirm the added value of integrating detailed urban data, such as Local Climate Zones (LCZs). Methods to extract urban areas and their surroundings from RCM data are advancing nevertheless remain challenging, especially across spatial resolutions.

Looking ahead, the next phase of FPS URB-RCC Paris region simulations and the Global Satellite Cities approach will extend investigations to longer time periods and urban areas globally, including vulnerable regions. 

In summary, the FPS URB-RCC demonstrates that RCMs can offer advanced urban climate projections and deepen our understanding of the relationship between cities and regional climate change.

How to cite: Langendijk, G., Halenka, T., Hoffmann, P., Fernández, J., Diez-Sierra, J., Demuzere, M., le Roy, B., Lemonsu, A., Michau, Y., Belda, M., Rechid, D., Coppola, E., Zazulie, N., Nogherotto, R., Fita, L., Milovac, J., and community, F. U.: Urban Areas under Climate Change: What Regional Climate Models Reveal at Different Scales, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-879, 2025.

Climate change is intensifying the frequency and severity of environmental hazards, affecting urban and rural areas in distinct ways. Cities can experience amplified risks due to the urban heat island (UHI) effect, altered precipitation patterns, and increased exposure to extreme weather events. Meanwhile, rural areas face vulnerabilities linked to droughts, wildfires, and agricultural losses, which can have cascading socio-economic impacts. Hazard indices serve as critical tools to quantify and compare these risks, providing insight into how different areas respond to climate stressors. 

In this study, we analyze climate extreme indices using regional climate models (RCMs) from the Euro-CORDEX ensemble, specifically those incorporating urban representations. We focus on ten of the largest cities in Europe and their surrounding rural areas, using high-resolution (12 km) historical and RCP8.5 projections to evaluate changes in selected indices. The results are expressed in terms of global warming levels (GWLs), allowing for a consistent comparison across members.

Our findings highlight not only the presence of the UHI effect but also its amplification as global temperatures rise. The differences in climate extremes between urban and rural areas become more pronounced with increasing GWLs, underscoring the need for targeted adaptation measures. Understanding how hazard indices evolve across warming levels is crucial for developing climate-resilient policies and strategies tailored to both urban and rural settings.

How to cite: Zazulie, N., Nogherotto, R., Coppola, E., Raffaele, F., and de Leeuw, J.: Assessing Climate Change Hazards in Urban and Rural Areas for European Cities Using Euro-CORDEX ensemble, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-757, https://doi.org/10.5194/icuc12-757, 2025.

Urban areas are responsible for about 70% of global greenhouse gas emissions, contributing to global climate change. At the same time, cities and, in particular, urban populations are severely affected by climate change. For example, the projected increase in heatwaves has negative impacts on human health, and the increase in heavy precipitation events can cause urban flooding. In addition, temperature, precipitation and other atmospheric variables such as wind and humidity are known to be influenced by urban areas. These urban impacts can vary greatly from city to city, and for local time of day, and may be influenced by climate change. However, a global analysis of these effects is still rare.

Using simulations at 50 km resolution with the global Conformal Cubic Atmospheric Model (CCAM) coupled to a state-of-the-art urban parameterization, we analyze the impact of urban areas on the diurnal cycle of atmospheric variables in the current climate and in a future climate based on the RCP8.5 scenario. First, we generated time zone-corrected three-hourly Local Time Period (LTP) data to compute mean diurnal cycles for grid cells with more than 10% urban fraction for the two periods 1985-2010 and 2070-2099. Second, we grouped the data into latitudinal bands: Northern Extratropics (NET), Southern Extratropics (SET) and Tropics. For the current climate, we found statistically significant urban influences on temperature at night, consistent with many previous studies on urban heat islands and evidence of urban cooling during daytime. For NET, two-thirds of the urban grid cells show significantly increased precipitation, while for SET and Tropics show more decreases than increases. The urban impact on the precipitation signal in the future time period is small, while urban areas alter the signal of temperature and specific humidity in NET with a tendency towards reducing the increases in both variables.

How to cite: Hoffmann, P., Katzfey, J., and Schlünzen, K. H.: Urban effects on current and future diurnal cycle of atmospheric variables in global climate simulations, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-890, https://doi.org/10.5194/icuc12-890, 2025.

Cities are particularly vulnerable to climate change, which continues to drive rising air temperatures. The morphology of a city also influences local climate through diverse surface properties and configurations, leading to varying responses to increasing air temperature trends. This study examines the impact of climate change on Santiago, Chile, a city in a valley characterised by a semi-arid climate. We analysed near-surface air temperature and rainfall data measured by the Chile Bureau of Meteorology stations sited in three different local climate zones (LCZ) over the last 63 years. The three LCZs were localised in the peri-urban, inner-city and residential areas. The methodology was conducted with regression analysis, a seasonal time series model, and standardised anomalies to assess temperature and rainfall trends. The results indicate a higher rate of warming and a greater decline in precipitation in the peri-urban area compared to the inner-city and residential areas, in addition to a doubling of the warming rate in recent years. The daily temperature range (DTR) exhibited a negative trend in the peri-urban area but a positive trend in the inner-city and residential areas, reflecting differences in the warming rates of maximum and minimum temperatures. Additionally, the peri-urban area displayed significant intra-annual variability in temperature and rainfall within the seasonal cycle. However, smaller temperature changes at the beginning of the study period were presented in the peri-urban area but much larger ones towards the end, in contrast to the other areas. Our findings underscore the accentuated impact of climate change in the peri-urban area due to its permeable surface characteristics without vegetation, compared to the areas dominated by impermeable surfaces with or without vegetation. It highlights the importance of analysing urban air temperatures based on LCZs, challenging the conventional urban-rural temperature difference paradigm that underpins urban heat island assessments.

How to cite: Moncada-Morales, G. A., Livesley, S. J., Nice, K., Pianella, A., and Carpio, M.: Urban climate variability in a warming world: Analysing long-term urban air temperature and rainfall trends in Santiago, Chile (1961–2024), 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-517, https://doi.org/10.5194/icuc12-517, 2025.

The current global trend of heatwave events is becoming increasingly frequent and severe, closely linked to climate change and global urbanization processes. Studies have shown that urbanization exacerbates the urban heat island effect, thereby increasing the risk of heatwave events. Existing research often employs a binary urban-rural perspective to explore the impact of urbanization on heatwaves. However, the impacts of heatwaves on cities at varying stages of urban development—ranging from rapid growth to counter-urbanization—remain inadequately understood. This research addresses this gap by analyzing observational data from the Global Historical Climatology Network daily (GHCNd) over 1990–2020, classifying cities based on their urbanization processes (e.g., S-curve dynamics or counter-urbanization). We examine how these developmental stages correlate with heatwave frequency, duration, and exposure amplification—a novel metric reflecting the pressure of coping with heatwaves, calculated as the ratio of heatwave exposure growth to heatwave event increases. Results reveal that 22.2% of urban stations show statistically significant trends in heatwave metrics, with three-quarters experiencing increased heatwave days. Cities in medium or advanced urbanization stages exhibit pronounced heatwave escalation, while rural areas display divergent responses. Notably, cities in early urbanization phases face the strongest heatwave exposure amplification effects (exceeding 200%), indicating faster growth in exposure than in heatwave events. This effect diminishes with urbanization progress but, spatially, lower-latitude cities endure more severe amplification effects, compounding challenges in already high-temperature regions. In addition, rural areas adjacent to urban zones also show elevated vulnerability, with future projections under Shared Socioeconomic Pathways (SSPs) suggesting rural populations may face greater heat exposure risks than urban counterparts. The study provides targeted insights for policymakers to design adaptive strategies, emphasizing the necessity of considering urbanization stages in climate resilience planning.

How to cite: Chen, G. and Ren, C.: Exploring heatwave in urban and rural areas across urbanization stages, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-268, https://doi.org/10.5194/icuc12-268, 2025.

This study examines climate drivers influencing urban heatwave metrics and interannual variability in Southern California from 1950–2020. The frequency, duration, and intensity of urban heatwaves are rapidly increasing with a greater tendency towards more humid and intense nighttime events at a rate of ~1°C/decade since the 1980s, elevating heat stress and mortality risk. Increased humidity is associated with an anomalous moisture source off the coast of Baja California, which intensified over the past decade, and linked to marine heatwaves and changes in the California current system. The interannual variability in heatwave events shows significant correlations between Pacific Decadal Oscillation modulations and heatwave frequency and duration for urban areas, irrespective of El Niño Southern Oscillation phases. The coupling of heatwave duration-intensity strengthens from the 1990s, with a longer duration occurring above a ~3°C intensity rise. Droughts and urban heatwaves are strongly linked, with a high statistical probability of increase in heatwaves frequency (42%), duration (26%), and daily mean temperature (2.2%) during severe drought conditions. Heatwaves now persist later in the year during peak fire season, potentially intensifying wildfires by enhancing aridity and drying out fuels. This can be disastrous when they coincide with strong Santa Ana winds as experienced in January 2025 across Altadena and Pacific Palisades in Los Angeles county. Better understanding of heatwave climate drivers and underlying physical processes could help with prediction skill and provide effective data‐driven recommendations for climate mitigation strategies in Southern California cities.

How to cite: Dousset, B., Hulley, G. C., and Kahn, B. H.: Rising trends in urban heatwave metrics and their climate drivers in Southern California, from 1950–2020, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-326, https://doi.org/10.5194/icuc12-326, 2025.

Creating city-wide maps of the canopy-layer urban heat island, or the spatial variation of air temperature within the canopy layer, generally requires the use of an urban climate model. This model must be able to resolve the complex energy exchanges between the urban surface and the atmosphere as well as the detailed atmospheric physics near the city surface at a sub-kilometer resolution. As a result, significant computational resources are necessary. Simpler statistical approaches are available but often restricted to specific weather conditions (e.g. maximum nighttime urban heat island intensity). Here we use a computationally and methodologically simple approach which relates local climate zones to canopy-layer air temperature to generating maps of the urban heat increment in reference to a specific local climate zone across Singapore Island for different periods of the day, different seasons and weather conditions. By utilizing historical land cover maps alongside projections for future urban development, it is possible to estimate how this temperature increase has evolved over time and how it may change in the future. Finally, by integrating global warming projections, future canopy-layer air temperatures can be determined. Initial results suggest a present-day extra ~1.0ºC warming due to the presence of urban areas across Singapore Island considering area-weighted distribution of LCZs and all-weather daily averages. This urban-induced warming is therefore of similar magnitude to that caused by anthropogenic global warming. Following the introduction of the long-term canopy-layer air temperature observations essential to the methodology, the presentation will show how urban heat levels have changed during Singapore's rapid development over the past 60 years, alongside future projections using recent high-resolution local climate projections for this tropical area.

How to cite: Roth, M., Patel, P., and Sanchez, B.: Mapping Urban Heat Islands for Estimating City-Wide Heat Increases in Relation to Background Global Warming, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-400, https://doi.org/10.5194/icuc12-400, 2025.

Research on the synergy between urban heat islands (UHI) and heat waves (HW) in tropical cities remains scarce, despite the increasing frequency, duration, and severity of HW in Southeast Asia. Studies indicate that UHI intensity (UHII) can increase (positive), decrease (negative), or remain unchanged (neutral) during HW. This study investigates two HW events in 2016 (Case 1) and 2020 (Case 2) to understand the UHI-HW synergy in Greater Kuala Lumpur (GKL). The Advanced Research WRF (ARW) model version 4.2.2, coupled with a single-layer Urban Canopy Model (UCM), was employed to assess UHI impacts during these HW events in GKL, comparing them with periods immediately before and after the events, referred to as Pre-Post HW (PPHW). Results demonstrate that UHII is enhanced during HW in both observations and simulations. The maximum observed UHII values were recorded at noon, reaching 2.3°C at 16:00 LT in Case 1 and 3.7°C at 15:00 LT in Case 2. This corresponds to increased daytime radiation, with the most pronounced variations recorded at 15:00 LT (433.0 W/m²) in Case 1 and at 16:00 LT (243.1 W/m²) in Case 2. The average cumulative sensible heat flux (Q_H) difference was notable, reaching 289.7 W/m² in Case 1 and 135.0 W/m² in Case 2 for urban areas, and 498.5 W/m² in Case 1 and 286.9 W/m² in Case 2 for rural areas. The Bowen ratio consistently increased during the transition from HW to PPHW conditions. Consistently across all measurement methods, the evidence indicates a clear and positive synergy between UHI and HW in GKL. This study provides valuable insights for future urban planning and mitigation strategies, particularly for tropical regions vulnerable to extreme weather events.

How to cite: Syed Mahba, S. F. and Kusaka, H.: Synergistic Effects of Urban Heat Island and Heat Waves in the Greater Kuala Lumpur Region, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-549, https://doi.org/10.5194/icuc12-549, 2025.

Outdoor thermal comfort is a crucial indicator for assessing urban livability. With the intensification of climate change and the urban heat island effect (UHI), thermal comfort in Taiwanese cities has gradually deteriorated. This study analyzes changes in outdoor thermal comfort in two major cities—highly urbanized Taipei and rapidly urbanizing Taichung—using the Universal Thermal Climate Index (UTCI) from 1990 to 2023. Hourly climate data (temperature, humidity, solar radiation, and wind speed) from both city centers and suburban coastal areas were collected and used to calculate hourly UTCI values. Additionally, annual overheating hours and their severity were examined. The results show that, although Taipei is located in a cooler climate zone, its annual overheating hours and severity have exceeded those of Taichung over the past 34 years, along with a higher growth rate. Particularly the growth rate, Taipei’s annual growth rate is approximately 1.6 to 1.8 times that of Taichung. Analysis of the urban and suburban data reveals that Taipei’s urban expansion has already impacted the surrounding suburban areas, accelerating the deterioration of thermal comfort, with a discomfort growth rate approximately twice that of the city center. In contrast, Taichung’s suburban areas have not yet experienced significant urban development, resulting in a growth rate of thermal discomfort that is only one-third to one-half of that in the city center. Overall, the findings highlight that the impact of the UHI effect on thermal comfort far outweighs that of climate change. As urbanization continues, the negative effects of UHI will become increasingly significant.

How to cite: Shih, L. C., Huang, K.-T., and Hwang, R.-L.: Exploring the Long-Term Trends of Outdoor Thermal Comfort Under Urban Heat Island and Climate Change Effects in Taiwan’s Cities, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-572, https://doi.org/10.5194/icuc12-572, 2025.

The increasing frequency of heat waves in high-latitude regions emphasizes the necessity for a deeper understanding of their impacts on urban areas and residents. This study, conducted within the BRIGHT project, presents an innovative methodology for assessing urban heat stress by integrating event-based downscaling using dynamical climate model, low-cost sensor deployment, and citizen sensing approaches.

This study explores results from a network of low-cost thermohygrometers (2022-2024) in three Swedish cities (Stockholm, Norrköping, and Linköping) and climate simulations for normal, hot, and extreme hot summers under specific warming levels (SWL) of +0.9°C (historical), +2°C, and +3°C. The methodology employs the downscaling modelling approach, utilizing the HCLIM43-AROME convection-permitting regional climate model up to 3km resolution, the SURFEX land surface model at 300m, and the SOLWEIG radiation model at 1m resolution for detailed local assessments. SOLWEIG calculates mean radiant temperature (MRT), a key indicator of human thermal comfort.

The results reveal that the shade of foliage and buildings has a clear cooling effect, with parks reducing the MRT by over 20°C. For the “hot” and “extreme hot” summers (historical climate), the number of hours with a 5% increase in mortality risk varies up to 200 hours in the parks under historical period, while central areas of the cities, with sparse tree canopy, face 250-400 hours of such risk. Under the +3°C SWL, these ranges increase by 50h. When comparing SWL +3°C to historical conditions, the relative differences in heat stress are more pronounced for "normal" and "hot" summers than for "extreme hot" summers, indicating a trend, where the existing vegetation coverage becomes ineffective at mitigating the heat

These insights underscore the importance of holistic, climate-informed urban planning strategies that prioritize green infrastructure, consider varying warming scenarios, and address both extreme and moderate heat conditions to more liveable cities in a climate changing context.

How to cite: Ribeiro, I., Segersson, D., Aldama-Campino, A., Wang, F., Wingstedt, E., Asker, C., and Amorim, J. H.: High-resolution urban heat stress modelling: event-based downscaling in Swedish cities, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-604, https://doi.org/10.5194/icuc12-604, 2025.

Urban expansion is a key contributor to near-surface temperature increases in modified landscapes. While much of past research has examined the impact of urban areas on downstream non-urban regions, the influence of thermal advection from upstream urban development on existing urban areas remains underexplored. In this study, we analyze historical temperature records for rapidly and non-rapidly expanding cities in the southwestern U.S. to determine the primary drivers of warming trends.

Our findings reveal that Phoenix, AZ, and Las Vegas, NV, exhibit significant warming trends in minimum temperatures (Tmin), with rates of 0.835°C/decade and 0.802°C/decade, respectively, alongside reductions in diurnal temperature ranges of -0.506°C/decade and -0.664°C/decade. Conversely, non-rapidly expanding cities such as Williams, AZ, and Flagstaff, AZ, show minimal Tmin increases of 0.005°C/decade and 0.21°C/decade, with much smaller diurnal cycle changes of +0.035°C/year and -0.0073°C/decade, respectively.

We quantified the impact of thermal advection using the Weather Research and Forecasting (WRF) model and semi-Lagrangian simulations to assess the role of upstream urban expansion on observed temperature trends at Phoenix Sky Harbor International Airport. Simulations for June 2002 and June 2019, under various urban extent scenarios, align with long-term observational data, confirm upstream urban expansion as the dominant driver of warming. Simplified semi-Lagrangian simulations further validated these results, demonstrating that thermal advection contributes to rising Tmin and declining diurnal cycles.

This study highlights the utility of the semi-Lagrangian model as a computationally efficient tool for prediction of future Tmin trends driven by urban growth. The findings have broad implications for managing warming in semi-arid cities worldwide.

How to cite: Moustaoui, M. M. and Georgescu, M.: Urban Heat in Motion - How Expansion and Thermal Advection have Shaped Phoenix’s Warming Trends , 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-818, https://doi.org/10.5194/icuc12-818, 2025.

We analyse two 30-year long global, fully coupled Earth-System simulations at a spatial resolution of around 9 km. The first simulation covers the recent decades from 1990-2020, while the second simulates a future SSP3-7.0 scenario, usually leading to one of the warmest future climates, during the period 2020-2050. These simulations are the first multi-decadal simulations at kilometre-scale resolution with an explicit representation of urban areas. These unique simulations enable us to study the two-way interactions between cities and regional climates globally, the evolution of urban climates across the recent decades, as well as the projected changes in the period 2020-2050 for cities worldwide.

The accuracy and associated uncertainties of the urban climate representation were assessed by comparing present-day simulations against surface temperature observations from LSA-SAF over a wide range of major cities. This data set provides relevant observations at a high spatio-temporal resolution and covers most of the globe. It therefore allows for a spatially consistent validation of the thermal impact of urban areas. This analysis is of particular interest for regions with scarce in-situ surface observations and/or limited regional/local simulations.  

We explore the classification of cities with differing characteristics, e.g.  regional topography, morphology or local climates, for a comprehensive global analysis of urban climates. We also investigate past and future trends for these city groups and attempt to classify urban areas around the globe in terms of expected shifts in climate.

How to cite: Sützl, B., Pedruzo-Bagazgoitia, X., Dutra, E., McNorton, J., Rüdiger, C., and Tsiringakis, A.: Urban climate in km-scale climate simulations under historical periods and future scenarios, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-297, https://doi.org/10.5194/icuc12-297, 2025.

Cities constitute a crucial issue in the current and future environmental challenges, and they are highly exposed to extreme events, particularly high heat for the Paris region. This calls for a fine and explicit representation of cities in climate models to identify spatial disparities of the impacts of climate change. The Convection-Permitting Regional Climate Model CNRM-AROME (2.5 km) coupled to the TEB urban canopy model is suitable to conduct impact studies at city- and region-scale, considering climate evolutions. 

However, spatial dynamics of cities, such as urban sprawl or densification, are not represented in CNRM-AROME. Currently, the ECOCLIMAP-I land use map, based on CORINE Land Cover pan-European data from the 1990s, is used to characterise the surface properties, whether for simulations in present climate as well as for future climate projections. 

With the Paris region as a case study, three climate simulations of the past period 2000-2022 were carried out with the CNRM-AROME model, according to three land use scenarios (urbanisation of 1990, 2018 and 2050). These simulations allow us to quantify the effect of urbanisation on regional climate and its contribution on the warming trends in the Paris region. By a comparison with available observation data, we also assess the added-value of the actualised land use map against the default one. These results underline the importance of taking urban dynamics into account in the regional climate models, to better map the local impacts of climate change over urban areas and their surroundings.

How to cite: Corneille, L., Lemonsu, A., Viguié, V., Caillaud, C., and Machado, T.: How does the development of cities influence regional climate? A case study on the Paris region with the Convection-Permitting Regional Climate Model CNRM-AROME., 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-398, https://doi.org/10.5194/icuc12-398, 2025.

How to cite: Fenner, D., Meier, F., Holtmann, A., Otto, M., and Scherer, D.: Recent unprecedented warming in Berlin, Germany, not influenced by urban effects, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-428, https://doi.org/10.5194/icuc12-428, 2025.

Buenos Aires, Argentina, is one of the world’s megacities. The metropolitan area of Buenos Aires extends for around 4000 km2 and has 14 million inhabitants. As climate change intensifies, local existing social and environmental challenges exacerbate the need for an updated portfolio that considers all climate change strategies, including solar geoengineering or Solar Radiation Modification (SRM), which consists of ideas aimed at slowing or halting global warming by reflecting a small portion of sunlight away from the Earth. This study explores the potential risks and benefits that SRM in the form of stratospheric aerosol injection (SAI) would bring to the urban climate of Buenos Aires in comparison with the risks and benefits of ongoing and projected local climate change. This solar geoengineering technique introduces changes in atmospheric conditions that are quantified and evaluated at the urban scale through the bias correction and statistical downscaling (BC) of the ARISE-SAI-1.5 climate simulations designed to be policy relevant as they aim to maintain global surface temperatures at ∼1.5°C above pre-industrial levels. We evaluate the potential impacts of SAI at local scale compared to the impacts under the intermediate SSP2–4.5 scenario. Quantitative information on changes in daily mean and extreme precipitation and temperature for Buenos Aires under SAI and the SSP2–4.5 scenarios were computed for different future time slices. Results indicate that the avoided warming for Buenos Aires varies based on the BC method used when comparing the SAI and non-SAI scenarios. For the period 2035-2049, the maximum and minimum temperature reductions range from 0.3°C to 0.4°C. In 2055-2069, the reduction in temperature increases to between 1.3°C and 1.4°C. Additionally, the non-SAI scenario is projected to be wetter than the SAI scenario, with increases in rainfall of 1.1% to 1.7% for 2035-2049 and 3.8% to 5.4% for 2055-2069.

How to cite: Camilloni, I. and Raggio, G.: Impacts of climate change and solar geoengineering on the local climate of a megacity: A case study of Buenos Aires, Argentina, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-524, https://doi.org/10.5194/icuc12-524, 2025.

The Urban Heat Island (UHI) effect, driven by anthropogenic environmental modifications, heightens heat risks in urban areas. Climate change is already accelerating global temperatures. This effect is being further exacerbated with rapid urbanization with the effects of UHI posing critical challenges to human health and urban infrastructure.  Urban planners and decision-makers require robust tools to quantify UHI effects under diverse climate and socioeconomic scenarios to address this. Currently, urban canopy models (UCMs) are implemented in numerical weather prediction models. They generate temperatures in urban areas at comparatively high resolutions that cannot be achieved with Regional Climate Models (RCMs). However, using UCMs coupled to atmospheric models is computationally expensive and requires users to acquire detailed urban canopy parameters (UCPs), which is arduous, especially for rapid future urban planning focussed scenario modelling.

This study introduces an innovative geospatial framework consisting of a GPU-based UCM implementation coupled with an in-canyon vegetation model. This framework streamlines the modelling process through a built-in geospatial toolkit capable of pre-processing UCPs from either openly available urban datasets or user-supplied high-quality data. The GPU-based implementation significantly enhances computational efficiency, enabling UHI simulations with a standalone UCM at high spatial resolutions. This framework empowers planners to simulate UHI under various future climate and urban development scenarios by integrating climate projections and socioeconomic data. The resulting UHI predictions can identify high-risk areas, prioritize adaptation strategies, and inform climate adaptation planning for rapidly expanding cities. This research provides a transformative yet practical approach to UHI modelling, equipping urban decision-makers with an accessible, high-performance tool to confront the challenges of climate-driven urban heat risks.

How to cite: Weeraratne, V., Garg, N., Cohen, R., Pauwels, V., and Prakash, M.: A Geospatial Framework for Efficient Urban Heat Island Modelling and Risk Assessment under Future Urban Climate Scenarios, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-254, https://doi.org/10.5194/icuc12-254, 2025.

Urbanization has historically been linked to increasing carbon emissions, driven by carbon-intensive consumption patterns. While urbanization fosters societal benefits, such as improved living standards, it also amplifies resource consumption, biodiversity loss, spatial constraints, and climate risks. The systematic analysis of the environmental impact that different settlement morphologies have at local and global level, as well as its vulnerability to a changing global climate remains underexplored. This knowledge gap hinders efforts to foster sustainable transformation and enhance resilience across urban systems. Given that climate change impacts transcend administrative boundaries, a holistic understanding of urban systems, their settlement types, and interlinkages is essential for devising solutions that operate across scales, sectors, and promotes an effective stakeholder participation.
The joint research project Urban Climate Futures Lab explores intricate relationships between urban development, climate impacts, and mitigation strategies, through the built environment and open spaces. Focusing on Lower Saxony, we explore these complex relationships systematically for all of its 42,000 settlement units of different characteristics covering 3,800km2 with 6,7 million people, as well as its potential extrapolation to broader contexts.
In this paper we discuss a systematic method to analyze the implications that projected climate scenarios—from the 12.5km resolution EURO-CORDEX regional climate simulation ensemble—have on urban areas in Lower Saxony. We achieve this by defining a framework for the interpretation of global, regional and—eventually—local climate information and the impact of climate change on urban settlements through the TOPOI-method. This provides a detailed understanding of how different settlement typologies are affected under different climate scenarios. This reveals distinct vulnerabilities linked to specific urban forms. The results will support the development of evidence-based strategies for mitigating climate risks and enhancing resilience across diverse urban contexts. The methodology and findings could be transferred to other regions, fostering broader applicability and impact.

How to cite: Zeringue, R., Teichmann, C., Mumm, O., Muñoz, E., and Carlow, V.: Analyzing Climate Impact across the Urban-Rural system through the TOPOI Method in Lower Saxony, Germany, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-773, https://doi.org/10.5194/icuc12-773, 2025.