Mean Radiant Temperature (MRT) has emerged as a critical parameter for evaluating human thermal comfort in built environments and microclimates across the globe. Defined as the uniform temperature of an imaginary enclosure where the radiant heat exchange with the human body matches that of the actual, non-uniform environment, MRT offers a comprehensive representation of radiative thermal exposure. Understanding MRT requires examining its relationship with human thermal indices, long-term fluctuations in outdoor settings, and impacts on human health and climate change patterns. This is a relevant topic for urban and landscape planners, architects, urban designers and health professionals, with accurate MRT assessment recognized as key to developing thermally comfortable spaces. Precise MRT measurement benefits occupants through improved thermal comfort conditions and energy efficiency. Furthermore, implementing MRT-informed design strategies helps reduce cooling demands, making it more affordable to maintain comfortable indoor and outdoor environments. This 'ten domains contribution' provides an overview of MRT's importance in human thermal comfort assessment, measurement and modelling techniques, relationships with indoor and outdoor environmental characteristics, implications for health studies and exposure during extreme heat events and heat waves, optimization strategies for buildings and HVAC systems, and future perspectives in the context of global to local climate change.

In an era of changing climate, rapid urbanization, and densification there is a need for spaces that can manage extreme weather events, such as heat waves and heavy precipitation, whilst simultaneously be attractive for the urban citizens, i.e., multifunctional spaces. In this paper a framework for integrated assessment of the potential of multiple urban blue-green infrastructure (BGI) elements to provide climate regulating and social functions, i.e. multifunctionality potential, based on best research available, in relation to cost for construction and maintenance to be used in planning is presented. The assessment of functions and costs is done on a nominal scale from 1 to 5 using a mixed-method approach (systematic literature review, model simulations and workshops). The integrated assessment is presented in a multifunctionality potential and cost matrix and allows for weighting of each function and cost, as their relative importance is context dependent. It is shown that the majority of BGI elements have a relatively low potential to provide multifunctionality in terms of urban stormwater management, heat stress reduction and recreation. Some of them to a low cost (e.g., road verges, ditches, permeable pavements) others to a high cost (e.g., green roofs and walls). The highest multifunctionality potential is found in large parks, but to a high cost. The most favourable element, i.e., high potential in relation to costs is urban forests. The matrix presented here is considered usable for making general well informed integrated decisions in planning and to enhance the awareness of single and multiple functions of BGI elements.

In the face of a warming climate and an ageing population, developing age-friendly urban areas is increasingly important. This study investigates the impact of the urban environment and socio-demographic factors on older adults' perceptions of indoor heat and outdoor activity during warm summers and heatwaves. The study takes a novel approach, incorporating survey data from older adults (age 64-92, n = 348) living in southwestern Sweden, with data on tree canopy coverage, building volume, and distance to water from geographical information systems (GIS). We further examine older adults' preferences for different types of urban environments during heatwaves and desirable environmental features during warm days. Results show that older adults living in areas with higher tree canopy coverage, close to parks, or with access to summer residences are less bothered by indoor heat during warm weather. Those living in urban areas with higher tree coverage and those having acess to a summer residences are less likely to avoid outdoor activity during heatwaves. Shade is the most desirable feature during warm days, with a majority seeking it in green areas. These findings highlight the importance of urban greenery and proximity to parks in ensuring outdoor activity, health, and well-being among older adults during warm summers and heatwaves.

Swedish buildings are well insulated for winter climate, but often not optimized for summer, leading to risks of overheating during heat extremes (including heat waves). Along with a warmer climate, the risks of overheating and need for cooling are expected to increase.In this study, present and future intensity, frequency and length of overheating, based on the newly implemented recommendations for indoor temperature from the Swedish Public Health Agency, is assessed for a typical Swedish multi-story residential building in Gothenburg, Sweden. Overheating is simulated for different floor levels and room orientations using the IDA-ICE building performance simulation software. The present climate (2008–2020) is represented by observed meteorological data and the future climate (2071–2100) by statistically downscaling the observations based on RCP4.5 simulations from the EURO-CORDEX project. Furthermore, the shading effect of trees at varying distances from the building is explored.Results show that overheating occurs during heat extremes from April to October, with the highest frequency in July. Overheating periods are projected to become more intense, more frequent and longer by the end of the century. During heat waves, overheating occurs throughout the day and may last for weeks, potentially impacting not only risk groups but also the general population. The risk of overheating increases with floor level and is largest for rooms facing west and south with large windows. Trees close to buildings considerably reduce overheating in the present as well as in the future warmer climate, highlighting their effective passive cooling potential during heat extremes.The results, which are considered applicable to a large part of the building stock in Sweden as well as in other countries with similar climate and building practices, highlight the present and future challenges with overheating and the potential of trees for mitigating overheating and reducing the cooling demand in buildings.

Urban citizens are particularly exposed to heat stress during heatwaves due to the urban climate conditions. Introducing more trees, changing building density and surface cover and materials are examples of planning measures that can be used to mitigate heat stress. One challenge as an urban planner is to have knowledge on which mitigation measure to implement to achieve the highest cooling effect with regards to outdoor heat stress at different spatial scales. The aim of this high-resolution modelling of outdoor thermal comfort on city-wide domains is to examine how different real-world urban settings reduce or exacerbate heat stress with regards to building density (plan area index), tree fraction, and ground cover. Here, we exploit the open-source tool Urban Multi-scale Environmental Predictor (UMEP), to investigate how real-world data on building density, tree fraction, and ground cover influence thermal comfort in the three largest cities in Sweden. Mean radiant temperature (Tmrt) and two thermal comfort indices are calculated and compared: Physiological Equivalent Temperature (PET) and Universal Thermal Comfort Index (UTCI). Automated chain processes using Python scripting is demonstrated, making it possible to derive microscale outdoor thermal comfort information (2-meter resolution) using a standard personal computer and open data sources. Results show that tree fraction is the single most effective outdoor heat mitigation measure, especially in areas with low building density. Results also show that building fraction has a minor cooling effect. This is probably due to the fact that shadowing at street level is dominated by trees due their 3D characteristics including trunk zones. Tmrt shows very similar results compared with PET and UTCI, indicating that Tmrt can capture the spatial variations of heat stress during warm, clear and calm days. Since trees is the single most effective measure to mitigate heat stress, it should be incorporated when creating practical guidelines to resilient urban planning strategies against heat stress.

In the context of the accelerating impacts of climate change on permafrost landscapes, we use an uncrewed aerial vehicle (UAV) carrying a lidar scanner to investigate seasonal terrain changes in palsas – mounds of frozen peat – since other remote sensing methods have struggled to capture the full dynamics of these landforms. We investigated two palsas (4–5 m in height) in Sweden's largest palsa mire complex, where we performed five field campaigns between September 2022 and September 2023 to track intra-annual frost heave and thaw subsidence. Our approach allowed us to create digital terrain models (DTMs) from high-density point clouds (> 1000 points m−2) and analyze elevation changes over time. We found that both palsas heaved on average 0.15 m (and up to 0.30 m) from September to April and subsided back to their height from the previous year, or slightly below, over the course of the following summer. At one of the palsas, we observed a notable lateral degradation hotspot over the study period in a 225 m2 area, with 0.5–1.9 m height loss, likely initiated during the preceding warm and wet summer months. Part of this degradation occurred between September 2022 and April 2023, suggesting that the degradation of these palsas is not limited to the summer months. Our study shows the substantial value of using UAV lidar for understanding how permafrost areas are changing. It facilitates tracking the ongoing effects of climate change and highlights palsa dynamics that would not be captured by annual measurements alone.

The importance of greenery for human well-being and recreation in urban areas is well-known. While many studies have examined the recreational importance of large green spaces, parks, and forests, the greenery encountered in our everyday surroundings, particularly in areas near our residences, has not been extensively researched. In this study, we investigated differences in tree canopy coverage, ground- and total amount of greenery among four common Nordic residential typologies, as well as how this greenery is perceived in terms of recreational values by residents. We utilized GIS-analysis and survey data for this investigation. The results revealed significant variations in urban greenery and recreational values between typologies, with modern dense residential areas being much less green and assessed to provide the least recreational values. Furthermore, the results suggest that trees and lawns play crucial roles in shaping residential areas that are pleasant to live in. These findings offer insights into the characteristics and challenges associated with the amount of greenery in various typologies, as well as preferences towards different types of greenery important for creating enjoyable outdoor residential environments. Finally, the results emphasize the importance of fine-scale investigation of greenery in residential areas.

Urban green–blue infrastructure (GBI) can provide important benefits to urban residents but may also affect mosquito abundance, with associated negative nuisance and infection transmission impacts. This study addresses important knowledge and quantification gaps for the relationships between mosquito prevalence and GBI features within cities. This is done for the city of Uppsala in Sweden as an urban case example, where mosquitos were captured and ambient air temperature and humidity were observed at seven different locations in the summer of 2022. A weighted multi-critera analysis (WMCA) model was developed based on relevant open data and open tools for resolving the mosquito ( Culex pipiens ) variations based on geographical variables, such as land cover/use, leaf area index, and building and green (vegetation) area fractions, within the city. The results show a clear relationship between mosquito prevalence and green-area fraction (of grass and trees), indicating that urban GBI extension can enhance mosquito prevalence, with possible associated negative impacts. This relationship is supported directly by data, showing significantly higher mosquito prevalence with higher ambient humidity, which in turn is related to larger green-area fraction. The developed WMCA model emerges as a promising tool, e.g., for urban development planning that needs to account for and seek relevant trade-off balances between positive and negative effects of urban GBI changes.

Heat stress can have negative effects on human wellbeing with morbidity and mortality as harmful consequences, especially in vulnerable groups, e.g. children, elderly and chronically ill. Children is for example at higher risk of dehydration and heat stroke compared to healthy adults. Furthermore, children attending preschools are endorsed to spend time outdoors and engaging in physical activities. Therefore, thermally comfortable preschool yards are detrimental to sustain safe environments where the children can continue their physically active play. Here we show that preschoolers in five Swedish cities, Malmö, Gothenburg, Stockholm, Östersund and Luleå, are exposed to heat stress on warm and clear days between May-August in preschool yards with insufficient shading, using three different thermal indices (COMFA, PET and UTCI). Furthermore, future number of heat stress days are evaluated using the SMHI RCA4 regional climate model from the EURO-CORDEX project, forced with six different global climate models. Results show that heat stress will increase under the RCP2.6, 4.5 and 8.5 climate change scenarios. In Malmö, Gothenburg and Stockholm number of days with heat stress all hours 09:00–15:00 while playing in a sunlit sandbox have doubled from approximately 10 to 20 days for 2071–2100 (RCP8.5) compared to 2008–2020. These numbers are even higher if active play, e.g. running, is performed, estimating to around two weeks in July alone by the end of the century. Without adaptation this is likely to have adverse effects on the health and learning of children. If the preschool yard, on the other hand, is shaded by trees, days with heat stress are almost entirely diminished, indicating the importance of trees in preschool yard design as a tool to mitigate heat stress.

Warm weather can have negative effects on the health and wellbeing of humans, especially risk groups e.g. children. Methods for estimating thermal comfort and physiological stress outdoors are not developed or adjusted for children. A consequence of this is few existing studies on children and thermal comfort and heat stress, particularly in a Swedish context. Children are at higher risk of heat stress than adults because of a larger body-surface-area to body-mass-ratio, lower sweat rate and that they are less aware of their thermal status. Swedish children attending preschool spend around three hours per day outdoors and the effects of weather and outdoor environment design on children’s thermal comfort are not clear. By better understanding how weather affects children's thermal comfort, measures can be taken to reduce heat stress and increase children's health and wellbeing. Here we present results from a project on the effect of warm weather on Swedish preschooler’s health and wellbeing. The results are based on detailed observations and simulations for present day climate as well as future climate change scenarios and give indications on exposure to heat stress and potential implications on the health and wellbeing of the children. For example, two thirds of preschool yards in Gothenburg are exposed to strong heat stress on clear and warm days. Strong heat stress have negative consequences for the pedagogic activities and wellbeing. Moreover, days with strong heat stress will increase in the future in exposed yards, whereas yards with sufficient shade are less prone to heat stress.

The Urban Multi-scale Environmental Predictor (UMEP) is a city based climate service tool that facilitate user-friendly open source capabilities to combine models and tools essential for climate simulations. The tool is designed for a broad range of users, both within academia as well as practitioners and non-expert users. UMEP is available as a plugin in QGIS, a free and open source geographic information system (GIS) available on all common platforms. One main purpose with UMEP is to include pre-processing of geo- and weather data, process calculations as well as post-processing and visualisation in the same tool.Recent developments in UMEP enables creation of all essential input variables required to generate high-resolution raster grid of common human thermal comfort indices such as Physiological Equivalent Temperate (PET), Universal Thermal Comfort Index (UTCI), Comfort Formula (COMFA) etc. This work presents initial results and methodology used to compute these indices within UMEP. Examples of workflow throughout the process, all the way to the final result, will be presented and discussed.

The importance of vegetation for human well-being and recreation in urban areas is well known. Many studies have examined the recreational importance of large green spaces, parks, and forests. But the vegetation we encounter in our daily lives, in environments close to homes, is less well studied. In this study differences of tree canopy coverage, low- and total amount of vegetation between four common Nordic residential typologies, and how the vegetation is perceived in terms of recreational values by residents is investigated using GIS-analysis and survey data. The results reveal an uneven and unequal access to residential vegetation and recreational values, with modern dense residential areas being much less green and assessed to provide least recreational values. Furthermore, the results indicate that trees, lawns and are most important blue-green elements for creating enjoyable residential areas. The findings offer insights into the characteristics and challenges associated with the vegetation supply in various typologies, as well as the preferences towards different types of greenery important for creating enjoyable outdoor residential environments. Finally, the emphasizes the importance of fine-scale investigation of vegetation supply in residential areas.

Hot weather conditions can have negative impacts on the thermal comfort and physical activity of vulnerable groups such as children. The aim of this study is to analyze the effects of warm weather on 5-year-old children's thermal comfort and physical activity in a preschool yard in Gothenburg, Sweden. In situ measurements were conducted for 1-1.5 h in the early afternoon on 8 days in May, June, and August of 2022. The thermal comfort and physical activity was estimated with GPS-tracks, heart rate monitors, and step counts and compared to observed weather conditions. Results show that physical activity decreases under warmer weather conditions, depicted by a decrease in distance moved, step counts, and highest registered pulse. Moreover, on warm days, the children avoid sunlit areas. For 50% or more of the time spent in sunlit areas, the children are exposed to cautious levels of heat. In shaded areas, on the other hand, the children are less exposed, with five out of 8 days having 50% or more of the time at neutral levels. The study demonstrates the importance of access to shaded areas in preschool yards where children can continue their active play while simultaneously maintaining a safe thermal status.

The Vissátvuopmi palsa complex (N 68°74′50′′, E 21°11′30”) is the largest coherent palsa complex in Sweden (ca 274 ha). Aerial photo-interpretation over an area covered by plateau palsas showed a 30% decline in lateral area -- from ca 70 to 49 ha -- that occurred between 1955 to 2016 (Olvmo et al., 2020). Within Vissátvuopmi, we have more closely studied two single palsas, one dome-shaped and one ridge-shaped, for changes in extent, height and vegetation composition. Manual interpretation of aerial photography between 1955 and 2016 show lateral degradation of 35% and 54% for the dome and ridge palsas, respectively. Since 2018 we have monitored the palsas using images from drones as well as analysis of Planet Dove and Sentinel-2 satellite imagery. Photogrammetry is used to produce orthophotos as well as digital surface models (DSMs) from the drone images, and compared to earlier LiDAR and aerial photo DSMs, to study lateral and vertical degradation. The drone-generated DSMs from 2018, 2019 and 2020 show further lateral degradation of the two large palsas. In 2020 a rapid change in vegetation composition was seen on the dome-shaped palsa, where a 250 m2 area of Betula nana and Empetrum hermaphroditum transitioned to lichen. This vegetation change could be seen in spectral data from both drone and satellite platforms. The future development of this palsa, monitored annually using both fine and medium spatial resolution data, will give insight into the timing and signs of the individual palsas in stages of degradation.

Using a mixed-method approach consisting of interviews with preschool teachers and modelling of the outdoor thermal conditions using the mean radiant temperature as an indicator of heat stress, the occurrence of heat stress in Gothenburg preschools during the summer of 2018 and its effects have been studied. One third of 440 preschool yards modelled have more than 50% of the preschool yard-area exposed to strong heat stress during a warm and sunny summer day, implying children in many preschools have considerably less play area than current guidelines deem sufficient. Shade, where present, was mostly from trees within the preschool yards themselves rather from objects in surrounding areas, provided effective heat mitigation. Interviews confirmed that excessive heat conditions at preschool yards resulted in tired, drowsy and overheated children as well as forcing the preschool to prioritise care over pedagogical activities. The results demonstrated that heat stress occurs at Gothenburg preschools, with difficulties in ensuring the well-being of children at many preschools as a consequence. Many preschools need more shade, preferably from trees to provide healthy and secure environments for preschool children. Finally, the study highlights the need for more research on how weather and outdoor environments affect children's activity and well-being.

Among several serious medical conditions, arrhythmia and heat stroke are two important causes of death during endurance races. Clinically, collapsing might be the first sign of these serious conditions and may mimic the more common and benign exercise-associated collapse. Several risk factors have been reported in the literature. We aimed to conduct a qualitative study to find a perceived risk profile among runners who collapsed and who were transported by ambulances to the nearest hospital during Gothenburg’s half marathon (2010–2017). Collapsing runners seem to lack the ability to make a decision to withdraw from the contest despite being exhausted. They feel the pain, but are unable to put meaning to their feeling, to adjust their pacing, and to handle other influences. Consequently, they do not overcome the problem or assess the situation. These individual mental characteristics may indicate a unique profile for collapsing runners. Pre-race health control and educational initiatives aiming at mental preparedness and information before endurance races might be a necessary step to avoid life-threatening complications.

BACKGROUND:The Wet-Bulb Globe Temperature (WBGT) index is a common tool to screen for heat stress for sporting events. However, the index has a number of limitations. Rational indices, such as the physiological equivalent temperature (PET) and Universal Thermal Climate Index (UTCI), are potential alternatives.AIM:To identify the thermal index that best predicts ambulance-required assistances and collapses during a city half marathon.METHODS:Eight years (2010-2017) of meteorological and ambulance transport data, including medical records, from Gothenburg's half-marathon were used to analyse associations between WBGT, PET and UTCI and the rates of ambulance-required assistances and collapses. All associations were evaluated by Monte-Carlo simulations and leave-one-out-cross-validation.RESULTS:The PET index showed the strongest correlation with both the rate of ambulance-required assistances (R2=0.72, p=0.008) and collapses (R2=0.71, p=0.008), followed by the UTCI (R2=0.64, p=0.017; R2=0.64, p=0.017) whereas the WBGT index showed substantially poorer correlations (R2=0.56, p=0.031; R2=0.56, p=0.033). PET stages of stress, match the rates of collapses better that the WBGT flag colour warning. Compared with the PET, the WBGT underestimates heat stress, especially at high radiant heat load. The rate of collapses increases with increasing heat stress; large increase from the day before the race seems to have an impact of the rate of collapses.CONCLUSION:We contend that the PET is a better predictor of collapses during a half marathon than the WBGT. We call for further investigation of PET as a screening tool alongside WBGT.

Substantial palsa degradation has occurred in Fennoscandia, which is considered to be driven by global climate change. Deeper understanding of the role of different climatic drivers on palsa decay, however, is lacking. We use meteorological data and aerial photographs from 1955 to 2016 to statistically identify the most important climatic drivers affecting changes in lateral-temporal palsa decay rates in the largest coherent palsa complex in Sweden, Vissátvuopmi. We show that wetter, warmer and shorter winters are the main causes of large and rapid changes in lateral-palsa extent since the mid-1950s. By analyzing meteorological data from the 1880s to present, we show that average annual temperature conditions have been unfavourable for palsas for more than a century and average annual precipitation conditions have been unfavourable since the 1940s. The decay rates have likely been amplified over the past 50-60 years, and in particular over the most recent decades, due to the combined effect of adverse air temperature and precipitation conditions. Palsa loss is expected to continue, most likely at a higher rate than today, with serious ecological impacts as a consequence.

During clear weather conditions the main part of the shortwave irradiance derives from sun direct-beam radiation. However, part of the shortwave radiation also originates from all-sky diffuse radiation (D), with a large part being circumsolar in origin. Many radiation models considers the sky as isotropic when estimating D. Here we implement an anisotropic model for D into the SOLWEIG model to examine the spatial patterns of D in a built-up environment, as well as its influence on mean radiant temperature (T-mrt), a variable essential for estimating outdoor human thermal comfort. Comparisons between the anisotropic and the isotropic models indicates that the D in the isotropic model is overestimated in shaded areas and underestimated in areas close to sunlit walls. This is explained by the circumsolar origin of D during clear and semi-cloudy conditions and solar altitude. These over- and underestimations, consecutively, have implications for T-mrt, which can differ by up to 3 degrees C. The deviations in D thus signify the importance of using an anisotropic model when estimating D and T-mrt, especially since the areas with the highest reported radiant loads receive even more radiation considering an anisotropic diffuse sky, i.e. the hottest areas are even hotter than previously reported.