Hot Days Research Articles

Testing Strategies for Planting Design in Urban Squares to Improve Human Comfort throughout the Seasons

Green urban squares are essential in densely built neighborhoods and enhance their quality of life. Investment in the greening of urban areas will have a beneficial impact, particularly regarding human thermal comfort. Smaller than parks, squares can be easily spread over the cities and should be part of any neighborhood. While the cooling effect of green squares during hot summer days is increasingly well established, microclimatic assessments during all seasons are still missing. This study aimed to determine whether it is possible to identify an optimal greenery design that maximizes human thermal comfort, as indexed by physiological equivalent temperature (PET), in temperate climates across all seasons. This study employed a “research by design” methodology, utilizing the micrometeorological simulation model ENVI-met to analyze the impact of greenery on PET improvement across different seasons. The objective was to identify the most effective combination of greenery for PET improvement. To achieve these objectives, two urban squares in Munich, Germany were selected. This selection was based on the assumption that typical greening practices, exemplified by the presence of trees, shrubs, and grass, would significantly impact urban squares and their microclimatic effects on human thermal comfort. The small square with a grass surface underneath trees, Alpenplatz, is highly influenced by the surrounding buildings, affecting the sky view factor (SVF), a crucial aspect of the urban environment. Marstallplatz, an open, large square that is not highly affected by urban morphology, was analyzed through simulation scenarios combining grass, shrubs, and trees. The results demonstrate that hot summer days are of primary concern for climate-sensitive urban square design in order to avoid health risks and thus need to be prioritized without compromising comfort for cold days. To attend to both needs, increasing the number of deciduous trees for shading during the day and the amount of grass to enhance air cooling at night are particularly effective. Nevertheless, microclimate design for the spring and autumn periods must also be considered, with the provision of adaptable opportunities for sheltered and sun-exposed spaces.

Systematic study of microzooplankton in mass culture of the green microalga Scenedesmus acuminatus and quantitative assessment of its impact on biomass productivity throughout a year

The green microalgae Scenedesmus spp. can grow rapidly and produce significant amounts of protein or lipid. However, frequent microzooplankton contamination leading to reduced biomass productivity has hindered the microalgae commercialization. Here, a comprehensive investigation into harmful microzooplankton species in mass cultures of a commercially promising species Scenedesmus acuminatus were conducted throughout the year. Twenty-five microzooplankton species were identified, with the amoeba Vannella sp. and the ciliate Vorticella convallaria being the most harmful to algal cells. The results indicated that it was the harmful grazers, rather than the overall microzooplankton diversity, led to culture deterioration and reduced biomass yield. Increasing the concentration of algal inoculants or reducing culture temperature during hot summer days were found to be effective in mitigating the impact of these harmful grazers. The findings will contribute to the best management protocol for monitoring and controlling the harmful microzooplankton in mass cultures of S. acuminatus.

Prioritising urban heat island mitigation interventions: Mapping a heat risk index

The global climate is under threat from increasing extreme heat, evidenced by rising temperatures and a surge in hot days. Heat waves are intensifying worldwide, impacting cities and residents, as demonstrated by the record-breaking heat experienced in the UK in 2022, which resulted in over 4500 deaths. Urban heat islands (UHIs) exacerbate these heat waves, making city residents more vulnerable to heat-related deaths. UHIs occur when temperatures in urban areas exceed those in surrounding rural areas due to the heat-absorbing properties of urban structures. Implementing mitigation strategies, such as green infrastructure, is crucial for enhancing urban resilience and reducing vulnerability to UHIs.Effectively addressing UHIs requires a systematic approach, including developing risk maps to prioritise areas for UHI mitigation strategies. Using remote sensing, GIS, and SPSS correlational analysis, the research aims to develop and assess a Heat Risk Index (HRI). This index integrates UHI spatial intensity, current green cover, and population density at the district level to develop the risk index. This study stands out for its novel approach to developing the HRI, focusing on the localised impact of the UHI in Manchester City, identifying high-risk heat-vulnerable districts, and prioritising implementing effective UHI mitigation strategies.The findings highlight the importance of this approach, revealing that approximately 30 % of Manchester City is affected by UHI effects, with areas near the city centre, characterised by higher population density and reduced green cover, being particularly vulnerable. Furthermore, the study suggests that applying HRIs at a more localised level, such as the neighbourhood level rather than the district level, would provide more relevant and targeted insights for mitigating UHI. A more localised index would offer tailored insights into the unique conditions of each neighbourhood within the districts, enabling more effective mitigation strategies. The HRI developed in this paper serves as a test for a more nuanced and comprehensive index, considering additional variables related to population vulnerability and city urban structure.

TEMPERATURE AND PRECIPITATION TRENDS DUE TO CLIMATE CHANGE IN THE HUIXTLA RIVER BASIN IN CHIAPAS, MEXICO

The objective of this work was to analyze whether there is a trend in climate change in the Huixtla River basin on the Mexican Pacific coast in the State of Chiapas. To detect this, temperature and precipitation trends were analyzed using data for the 1960–2014 period and the 27 indices proposed by the Expert Team on Climate Change Detection and Indices (ETCCDI) at Despoblado, Escuintla, Finca Chicharras, Huehuetán, Huixtla, and Motozintla weather stations of the National Meteorological Service (SMN). Missing data were collected where necessary for precipitation using the U.S. National Wheater Service method and for temperatures using the Climate Engine platform. The indices were obtained with RClimDex by conducting the proposed data quality controls and classified on the basis of their statistical significance (0.05) and their increasing or decreasing trend. Among the changes found, higher temperatures were detected in the middle and lower western parts of the basin (TX90p), as well as a longer period of hot days (WSDI). The upper and lower eastern parts of the basin presented a shorter period of hot days. The upper and lower parts of the basin showed a cooling trend, with colder days (TX10p) over longer periods (CSDI). Across the basin, precipitation has increased by one and five days (RX1day and RX5day) as well as in total amount (PRCPTOT). In general, there were shorter dry periods (CDD) and longer wet periods (CWD). Rainfall above the R5mm, R10mm, R20mm, R70mm, and R150mm thresholds across the basin showed an increasing trend.

Physiological and structural traits contribute to thermotolerance in wild Australian cotton species.

Five species of cotton (Gossypium) were exposed to 38°C days during early vegetative development. Commercial cotton (Gossypium hirsutum) was contrasted with four wild cotton species (G. australe, G. bickii, G. robinsonii and G. sturtianum) that are endemic to central and northern Australia. Plants were grown at daytime maxima of 30°C or 38°C for 25 d, commencing at the four-leaf stage. Leaf areas and shoot biomass were used to calculate relative rates of growth and specific leaf areas. Leaf gas exchange measurements revealed assimilation and transpiration rates, as well as electron transport rates (ETR) and carboxylation efficiency (CE) in steady-state conditions. Finally, leaf morphological traits (mean leaf area and leaf shape were quantified), along with leaf surface decorations, imaged using scanning electron microscopy. Shoot morphology was differentially affected by heat, with three of the four wild species growing faster at 38°C than at 30°C, whereas early growth in G. hirsutum was severely inhibited by heat. Areas of individual leaves and leaf numbers both contributed to these contrasting growth responses, with fewer, smaller leaves at 38°C in G. hirsutum. CO2 assimilation and transpiration rates of G. hirsutum were also dramatically reduced by heat. Cultivated cotton failed to achieve evaporative cooling, contrasting with the transpiration-driven cooling in the wild species. Heat substantially reduced ETR and CE in G. hirsutum, with much smaller effects in the wild species. We speculate that leaf shape, as assessed by invaginations of leaf margins, and leaf size contributed to heat dispersal differentially among the five species. Similarly, reflectance of light radiation was also highly distinctive for each species. These four wild Australian relatives of cotton have adapted to hot days that are inhibitory to commercial cotton, deploying a range of physiological and structural adaptations to achieve accelerated growth at 38°C.

Cool Roofs Could Be Most Effective at Reducing Outdoor Urban Temperatures in London (United Kingdom) Compared With Other Roof Top and Vegetation Interventions: A Mesoscale Urban Climate Modeling Study

AbstractComprehensive studies comparing impacts of building and street levels interventions on air temperature at metropolitan scales are still lacking despite increased urban heat‐related mortality and morbidity. We therefore model the impact of 9 interventions on air temperatures at 2 m during 2 hot days from the summer 2018 in the Greater London Authority area using the WRF BEP‐BEM climate model. We find that on average cool roofs most effectively reduce temperatures (∼−1.2°C), outperforming green roofs (∼0°C), solar panels (∼−0.5°C) and street level vegetation (∼−0.3°C). Application of air conditioning across London (United Kingdom) increases air temperatures by ∼+0.15°C. A practicable deployment of solar panels could cover its related energetic consumption. Current practicable deployments of green roofs and solar panels are ineffective at large scale reduction of temperatures. We provide a detailed decomposition of the surface energy balance to explain changes in air temperature and guide future decision‐making.

Historical and future extreme climate events in highly vulnerable small Caribbean Islands

Small Caribbean islands are on the frontline of climate change because of sea level rise, extreme rainfall and temperature events, and heavy hurricanes. The Archipelago of San Andrés, Providencia, and Santa Catalina (SAI), are Caribbean islands belonging to Colombia and declared a Biosphere Reserve by UNESCO. SAI is highly vulnerable to climate change impacts but no hydroclimatological study quantified the extreme climatic changes yet. This study analyzes historical (1960s-2020, 7 stations) and future (2071–2100, CMIP6 multi-model ensemble, for four scenarios: SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) trends in mean and extreme precipitation and temperature duration, frequency, and intensity. We find that heatwaves have more than tripled in frequency and doubled their maximum duration since the end of the ‘80 s. Precipitation is historically reduced by 5%, with a reduction recorded in 5 stations and an increase in 2, while extreme rainfall events significantly increased in frequency and intensity in most stations. The hotter-and-drier climate is amplified in the future for all scenarios, with much drier extremes (e.g., -0.5─-17% wet days, +8%─30% consecutive dry days, and +60%─89% in hot days). Although we show that hurricanes Categories IV and V near SAI (< 600 km) more than doubled since the’60 s, only a small fraction of extreme rainfall in the archipelago is associated with hurricanes or tropical storms. La Niña events also have no substantial influence on extreme precipitation. Interestingly, opposite and heterogeneous historical extreme rainfall trends are found across such small territory (< 30 km2). Thus, downscaled hydrometeorological data and model simulations are essential to investigate future extreme climatic events and strengthen small Caribbean islands' climate change adaptation efforts.

Vegetation reduces cooling demand in low-income neighborhoods on hot days in Chicago

Cooling energy demand is sensitive to urban form and socioeconomic characteristics of cities. Climate change will impact how these characteristics influence cooling demand. We use random forest machine learning methods to analyze the sensitivity of cooling demand in Chicago, IL, to weather, vegetation, building type, socioeconomic, and control variables by dividing census tracts of the city into four groups: below-Q1 income–hot days; above-Q1 income–hot days; below-Q1 income–regular days; and above-Q1 income–regular days. Below-Q1 census tracts experienced an increase in cooling demand on hot days while above-Q1 census tracts did not see an increase in demand. Weather (i.e. heat index and wind speed) and control variables (i.e. month of year, holidays and weekends) unsurprisingly had the most influence on cooling demand. Among the variables of interest, vegetation was associated with reduced cooling demand for below-Q1 income on hot days and increased cooling demand for below-Q1 income on regular days. In above-Q1 income census tracts building type was the most closely associated non-weather or control variable with cooling demand. The sensitivity of cooling demand for below-Q1 income census tracts to vegetation on hot days suggests vegetation could become more important for keeping cities cool for low-income populations as global temperatures increase. This result further highlights the importance of considering environmental justice in urban design.

Local hydroclimate drives differential warming rates between regular summer days and extreme hot days in the Northern Hemisphere

In this work, we compare the rate of warming of summertime extreme temperatures (summer maximum value of daily maximum temperature; TXx) relative to the local mean (summer mean daily maximum temperature; TXm) over the Northern Hemisphere in observations and one set of large ensemble (LE) simulations. During the 1979–2021 historical period, observations and simulations show robust warming trends in both TXm and TXx almost everywhere in the Northern Hemisphere, except over the eastern U.S. where observations show a slight cooling trend in TXx, which may be a manifestation of internal variability. We find that the observed warming rate in TXx is significantly smaller than in TXm in North Africa, western North America, Siberia, and Eastern Asia, whereas the warming rate in TXx is significantly larger over the Eastern U.S., the U.K., and Northwestern Europe. This observed geographical pattern is successfully reproduced by the vast majority of the LE members over the historical period, and is persistent (although less intense) in future climate projections over the 2051–2100 period. We also find that these relative warming patterns are mostly driven by the local hydroclimate conditions. TXx warms slower than TXm in the hyper-arid, arid, semi-arid and moist regions, where trends in the partitioning of the turbulent surface fluxes between the latent and sensible heat flux are similar during regular and extreme hot days. In contrast, TXx warms faster than TXm in dry-subhumid regions where trends in the partitioning of the surface fluxes are significantly different between regular and extreme hot days, with a larger role of sensible heat flux during the extreme hot days.

Extreme Temperatures and Stroke Mortality: Evidence From a Multi-Country Analysis.

Extreme temperatures contribute significantly to global mortality. While previous studies on temperature and stroke-specific outcomes presented conflicting results, these studies were predominantly limited to single-city or single-country analyses. Their findings are difficult to synthesize due to variations in methodologies and exposure definitions. Within the Multi-Country Multi-City Network, we built a new mortality database for ischemic and hemorrhagic stroke. Applying a unified analysis protocol, we conducted a multinational case-crossover study on the relationship between extreme temperatures and stroke. In the first stage, we fitted a conditional quasi-Poisson regression for daily mortality counts with distributed lag nonlinear models for temperature exposure separately for each city. In the second stage, the cumulative risk from each city was pooled using mixed-effect meta-analyses, accounting for clustering of cities with similar features. We compared temperature-stroke associations across country-level gross domestic product per capita. We computed excess deaths in each city that are attributable to the 2.5% hottest and coldest of days based on each city's temperature distribution. We collected data for a total of 3 443 969 ischemic strokes and 2 454 267 hemorrhagic stroke deaths from 522 cities in 25 countries. For every 1000 ischemic stroke deaths, we found that extreme cold and hot days contributed 9.1 (95% empirical CI, 8.6-9.4) and 2.2 (95% empirical CI, 1.9-2.4) excess deaths, respectively. For every 1000 hemorrhagic stroke deaths, extreme cold and hot days contributed 11.2 (95% empirical CI, 10.9-11.4) and 0.7 (95% empirical CI, 0.5-0.8) excess deaths, respectively. We found that countries with low gross domestic product per capita were at higher risk of heat-related hemorrhagic stroke mortality than countries with high gross domestic product per capita (P=0.02). Both extreme cold and hot temperatures are associated with an increased risk of dying from ischemic and hemorrhagic strokes. As climate change continues to exacerbate these extreme temperatures, interventional strategies are needed to mitigate impacts on stroke mortality, particularly in low-income countries.

Global Warming Impacts on Southeast Australian Coastally Trapped Southerly Wind Changes

Coastally trapped southerly wind changes are prominent during southeast Australia’s warm season (spring and summer). These abrupt, often gale force, wind changes are known locally as Southerly Busters (SBs) when their wind speeds reach 15 m/s. They move northwards along the coast, often producing very large temperature drops. SBs exceeding 21 m/s are severe SBs (SSBs). SBs have both positive and negative impacts. They bring relief from oppressively hot days but can cause destructive wind damage, worsen existing bushfires, and endanger aviation and marine activities. This study assesses the impacts of global warming (GW) and associated climate change on SBs and SSBs, using observational data from 1970 to 2022. Statistical analyses determine significant trends in annual frequency counts of SBs and SSBs, particularly during the accelerated GW period from the early–mid-1990s. It was found that the annual combined count of SBs and SSBs had increased, with SSBs dominating from 1970 to 1995, but SB frequencies exceeded SSBs from 1996 to 2023. The ascendency of SB frequencies over SSBs since 1996 is explained by the impact of GW on changes in global and local circulation patterns. Case studies exemplify how these circulation changes have increased annual frequencies of SBs, SSBs, and their combined total.

Factors affecting microhabitat use in two agamid species from south‐eastern Australia

AbstractDespite being a central aspect of a species' ecology and having important conservation implications, the use of fine‐scale habitat features (microhabitats), and how they vary over time, are poorly known for most species. In this study, we leveraged 522 relocations of radio‐tracked mallee tree dragons (Amphibolurus norrisi) and painted dragons (Ctenophorus pictus) to investigate the effect of environmental and individual variables on microhabitat use. Mallee tree dragons were more likely to use trees on hot days and in the middle of the day (the hottest time of day), whereas shrub use was more likely on cool days and in the mornings. Painted dragons were more likely to use shrubs and grass trees on warmer days and during the middle of the day, whereas burrows were used during cooler days and in the mornings and afternoons. We expect these patterns represent animals moving from refuge resources, occupied during unsuitable thermal conditions, to microhabitats offering basking, foraging and social opportunities during periods of thermal optimum. Additionally, we found evidence of an ontogenetic shift, with larger mallee tree dragons favouring tree use and higher perches, suggesting a transition from shrub to tree use with age. Our findings underscore the need for diverse microhabitats to accommodate the thermoregulatory and ontogenetic requirements of lizards. These insights can inform conservation and habitat restoration efforts, ensuring the provision of essential microhabitats to support species persistence.

Developing novel multifunctional protective clothes for disabled individuals using bio-based electrospun nanofibrous membranes

A novel kind of protective apparel for handicapped persons has been created with bio-based electrospun nanofibrous (NFs) membranes. Hydrophobic membranes with fine polylactic acid (PLA) NFs had a smooth, bead-less structure with an average diameter of 950 nm. The hydrophilic layer has a similar pattern but a smaller fiber diameter dispersion and an average diameter of 750 nm. The silica nanoparticle-modified super-hydrophobic top layer (contact angle, ~153°) repels water and keeps the user dry. Super-hydrophilic silver nanoparticles in the fabric's bottom layer react with perspiration to kill microorganisms. The fabric's porosity (avg. 1.2–1.5 μm) allows for breathability, while silica nanoparticles boost infrared radiation reflection, keeping users cool on hot days. The dual-layer textile has 4.9 MPa ultimate tensile strength and 68 % elongation compared to the membrane's super-hydrophobic and super-hydrophilic layers. Wearing protective clothes reduced hand temperature by 25 % in direct sunlight and 13 % in a sun simulator with 1 Sun. This fabric will work well for adult diapers, outdoor clothing, and disability accessories. Overall, the protective textiles may improve the quality of life for disabled and elderly people by providing usable textile items adapted to their needs.

The heat is on: Thermoregulatory and evaporative cooling patterns of desert-dwelling bats

For small endotherms inhabiting desert ecosystems, defending body temperatures (Tb) is challenging as they contend with extremely high ambient temperatures (Ta) and limited standing water. In the arid zone, bats may thermoconform whereby Tb varies with Ta, or may evaporatively cool themselves to maintain Tb < Ta. We used an integrative approach that combined both temperature telemetry and flow through respirometry to investigate the ecological and physiological strategies of lesser long-eared bats (Nyctophilus geoffroyi) in Australia's arid zone. We predicted individuals would exhibit desert-adapted thermoregulatory patterns (i.e., thermoconform to prioritise water conservation), and that females would be more conservative with their water reserves for evaporative cooling compared to males. Temperature telemetry data indicated that free-ranging N. geoffroyi were heterothermic (Tskin = 18.9–44.9 °C) during summer and thermoconformed over a wide range of temperatures, likely to conserve water and energy during the day. Experimentally, at high Tas, females maintained significantly lower Tb and resting metabolic rates, despite lower evaporative water loss (EWL) rates compared to males. Females only increased EWL at experimental Ta = 42.5 °C, significantly higher than males (40.7 °C), and higher than any bat species yet recorded. During the hottest day of this study, our estimates suggest the water required for evaporative cooling ranged from 18.3% (females) and 25.5% (males) of body mass. However, if we extrapolate these results to a recent heatwave these values increase to 36.5% and 47.3%, which are likely beyond lethal limits. It appears this population is under selective pressures to conserve water reserves and that these pressures are more pronounced in females than males. Bats in arid ecosystems are threatened by both current and future heatwaves and we recommend future conservation efforts focus on protecting current roost trees and creating artificial standing water sites near vulnerable populations.

Bat thermoregulation in the heat: seasonal variation in evaporative cooling capacities in four species of European bats

Phenotypic flexibility is an important source of physiological variation in endotherms and plays an integral role in species’ response to rapid environmental changes. Studies of phenotypic flexibility have focused on winter acclimatization and cold endurance, and there are fewer data on summer acclimatization and adjustments in heat dissipation capacity, especially in Temperate-Zone species. We used indirect calorimetry and thermometry to test if thermoregulation at high air temperatures (Ta) varies between spring and summer in four species of European vespertilionid bats: Nyctalus noctula, Pipistrellus nathusii, P. pygmaeus, and P. pipistrellus. We measured subcutaneous body temperature (Tsub), evaporative water loss, and resting metabolic rate while exposing bats to a stepped profile of increasing Ta, from 28 °C–48 °C. We predicted that during summer, bats increase heat tolerance and evaporative cooling capacity, to better tolerate hotter Tas. In contrast, we found lower maximum ratios of evaporative heat loss (EHL) to metabolic heat production (MHP) during summer, but no seasonal differences in maximum Ta tolerated or Tsub. The main cause of this seasonal difference in maximum EHL/MHP seems to be from bats increasing EWL more gradually with increasing Ta in summer than spring, particularly in the smaller Pipistrellus species. Therefore, this seasonal variation in heat-dissipation strategies may reflect enhanced water conservation during summer to avoid dehydration, as bats are confined to roosts for longer and hotter days compared to spring.

Climate Change Inculcate Crop Loss and Livelihood: A Case of Drought in Bangladesh

Crop loss is multidimensional and associated with drought and the consequences of climate change. Drought damages crops and make losses to the marginalized people and make them more vulnerable in different channels alike other disasters. The work has been carried out in the Northwest region of Barind in Bangladesh to explore relevant issues that may lead crop damage by frequent drought. Research used various methods in this study to get together both qualitative and quantitative information along with primary and secondary sources. Survey was conducted using semi-structured questionnaire with the sample population. Few selective case studies were made to obtain more information on crop loss and drought. In this study, Ordinary Least Square technique was utilized. The model of crop loss: C= α0 + α1X1 + α2X2 + α3X3 + α4X4 + α5X5 + α6X6 + α7X7 + α8X8 + α9X9 + µ1 The study explored few variables including income of the households, their age, sex and migration that have no important influence on crop production and loss owing to drought. Other variables such as frequency of drought, study areas, sustenance, livelihood and agricultural land have the significant influence on crop loss and livelihood. It was mentioned by the households that frequency of drought is increasing two decades with increase the number of hot days. Result indicates the meaningful relationship between drought frequency and crop losses. Few adaptation measures like re-sowing, early sowing, late planting can reduce crop loss. A wide range of alternatives for livelihood activities such as small business, van pulling, handiworks and seedling production for nursery business were identified by this study. Drought insurance policy, early warning system, future research on emerging issues and local level knowledge are important for climate change adaptation and resilience. IUBAT Review—A Multidisciplinary Academic Journal, 7(1): 171-185

The study of heat transfers and thermal performance of different types of solar box cookers

Solar fireplaces are important in remote areas with abundant solar radiation, they are a sustainable and environmentally friendly alternative to traditional cooking methods as they do not emit toxic gases. This study aims to experimentally compare solar box cookers of different designs, materials, and features to understand heat transfer and thermal performance to improve overall efficiency. Four different cases with different materials and features of the box structure are studied: Case 1 - non-tinted wooden sides, case 2 - black tinted wooden sides, case 3 - box with glass sides, and Case 4-black tinted wooden sides and coated inside with aluminum foil. Two designs are compared for each case- one with a front flat mirror and one without. All solar fireplaces consist of an inclined glass facing at an angle to the latitude of Baghdad and a base with black fins. The experiments lasted for three months in various weather conditions including cold, hot, dusty, and sunny days in southern Baghdad, Iraq, positioned at Latitude north and longitude East. Factors such as the intensity of incident radiation, wind speed, and ambient air temperature are taken into account during the cooking period. The results indicate that the third glass-sided box achieved the highest thermal efficiency of 93.7% after 120 minutes. The rice was fully cooked in just 97 minutes, the quickest time ever seen with this type of solar cooker, and it had a thermal efficiency of 88%. The fourth box, lined with aluminum foil inside, succeeded the third book with Rice reaching ripeness at 110 minutes with an 80.5% efficiency.

Anthropogenic influences on the extremely dry and hot summer of 2020 in Southern China and projected changes in the likelihood of the event

During summer 2020, Southern China experienced an extremely dry and hot summer, which was identified as one of the top ten domestic weather and climate extreme events in 2020 by China Meteorological Administration. Summer mean precipitation, surface air temperature (TAS), and number of hot days (NHD) were about 25% dryer, 1.5 °C warmer, and 11 days larger than the 1981–2010 climatologies. These are the 4th largest precipitation deficit, the highest TAS, and the 2nd highest NHD in the 1961–2020 record. The large-scale circulation anomalies over the West Pacific increased the likelihood of the extreme hot and dry summer. Anthropogenic influences on this extreme summerwere investigated using 525-member ensembles of the atmosphere-only HadGEM3-GA6 model and the multi-model ensembles from the Coupled Model Intercomparison Project Phase 6 (CMIP6). Anthropogenic forcings doubled (increased by 27%) the probability of precipitation deficits, and increased occurrence more than 106 times for both TAS anomaly (50 times probability higher) and NHD anomaly (6 times probability higher) in HadGEM-GA6 (CMIP6). That means that the 2020-like TAS and NHD anomalies would not occur without anthropogenic forcings, and there is weak evidence that human influences decrease rainfall over Southern China. However, the precipitation deficit increased the likelihood of exceeding the observed thresholds for both TAS and NHD by about 17 (4) and 9 (1) times in HadGEM3-GA6 (CMIP6), respectively. Under SSP2-4.5 and SSP5-8.5 scenarios in the future, 2020-like hot but wet extreme summer increases in magnitude and frequency, while the frequency of dry summer declines.

Feeling hot is being hot? Comparing the mapping and the surveying paradigm for urban heat vulnerability in Vienna

With rising global temperatures, cities increasingly need to identify populations or areas that are vulnerable to urban heat waves; however, vulnerability assessments may run into ecological fallacy if data from different scales are misconstrued as equivalent. We assess the heat vulnerability of 1983 residents in Vienna by measuring heat impacts, exposure, sensitivity and adaptive capacity with mirrored indicators in the mapping paradigm (i.e. census tract data referring to the geographic regions where these residents live) and the surveying paradigm (i.e. survey data referring to the residents' individual households). Results obtained in both paradigms diverge substantially: meteorological indicators of hot days and tropical nights are virtually unrelated to self-reported heat strain. Meteorological indicators are explained by mapping indicators (R2 of 15–40 %), but mostly not by surveying indicators. Vice versa, experienced heat stress and subjective heat burden are mostly unassociated with mapping indicators but are partially explained by surveying indicators (R2 of 2–4 %). The results suggest that the two paradigms do not capture the same components of vulnerability; this challenges whether studies conducted in the respective paradigms can complement and cross-validate each other. Policy interventions should first define which heat vulnerability outcome they target and then apply the paradigm that best captures the specific drivers of this outcome.

The Fantastic Story of How Cacti Thrive in the Brazilian Caatinga

In the sunny and dry land of Brazil’s Caatinga, a group of plants called cacti lives and thrives even though it does not rain much. But how do they do it? This article will take you on an adventure, in which you will learn how cacti survive in such a tough place. The Cereus cacti are like water-saving wizards, storing water in their bodies. Their spikes, which look and act like armor, also help them catch raindrops. Cacti have a cool way of making food. They do it at night when it is not too hot, to prevent themselves from losing water in the heat of the day. Cacti also have friends, like bats and hummingbirds, that bring pollen from one plant to another, helping the cacti to reproduce. The Caatinga can be a tricky place, with hot days and not much rain, but the story of Brazilian cacti reminds us of nature’s fascinating diversity and how life can be strong and beautiful, even in a very dry place.