Consecutive Hot Days Research Articles

Anthropogenic forcing has increased the risk of longer-traveling and slower-moving large contiguous heatwaves.

Heatwaves are consecutive hot days with devastating impacts on human health and the environment. These events may evolve across both space and time, characterizing a spatiotemporally contiguous propagation pattern that has not been fully understood. Here, we track the spatiotemporally contiguous heatwaves in both reanalysis datasets and model simulations and examine their moving patterns (i.e., moving distance, speed, and direction) in different continents and periods. Substantial changes in contiguous heatwaves have been identified from 1979 to 2020, with longer persistence, longer traveling distance, and slower propagation. These changes have been amplified since 1997, probably due to the weakening of eddy kinetic energy, zonal wind, and anthropogenic forcing. The results suggest that longer-lived, longer-traveling, and slower-moving contiguous heatwaves will cause more devastating impacts on human health and the environment in the future if greenhouse gas emissions keep rising and no effective measures are taken immediately. Our findings provide important implications for the adaption and mitigation of globally connected extreme heatwaves.

Extreme Heat Events over Southeast Europe Based on NEX-GDDP Ensemble: Present Climate Evaluation and Future Projections

Southeast Europe is considered one of the most vulnerable regions in the context of climate change, and projected future summer warming is expected to exceed global rates significantly. Despite the importance of this problem, there have been few studies that utilized Coupled Model Intercomparison Project Phase 5 (CMIP5) Global Circulation Models (GCMs) and the multi-model ensemble approach to examine extreme heat events on a regional scale. Additionally, the NEX-GDDP dataset, successfully applied in other parts of the world to assess extreme heat, has not yet been utilized for Southeast Europe. This study aims to fill that gap, presenting the time evolution and spatial distribution of extreme heat events in Southeast Europe for the historical period 1950–2005 and for the expected future climate up to the end of the 21st century based on the NEX-GDDP dataset. In order to leverage the strengths of the multi-model ensemble approach, a set of purpose-tailored indicators, such as the annual number of hot days, the maximum number of consecutive hot days, and hot spell duration at different thresholds, is computed by the daily maximum temperature data from all datasets, produced by NEX-GDDP (21 for the historical period and 42 for the future period). The E-OBS dataset is used as a reference for evaluating the NEX-GDDP’s capability to simulate the features of the observed historical extreme heat events. The results show that the multi-model ensemble can satisfactorily capture the occurrence of extreme heat events in the historical period, and therefore it is reasonable to assume that the NEX-GDDP dataset has the potential to reproduce such extremes in the projected future. The study provides clear evidence that the persistence and spatial extent of extreme heat will increase significantly. Some indicators that were not relevant for the historical period due to the high-temperature threshold will become helpful in assessing extreme heat in Southeast Europe in the latter part of the century. Thus, under the RCP8.5 scenario, the area-averaged duration of hot spells at 32 °C and 34 °C will increase from near zero in 1976–2005 to 60 and 45 days, respectively, by the end of the century. The indicators used in the study may be helpful for decision-makers to implement climate change mitigation strategies and actions adequately. The findings are consistent with general tendencies in maximum temperatures considered in our previous works but also with the outcomes of recent studies dedicated to the future climate of the region.

Acute association between heatwaves and stillbirth in six US states

BackgroundHeatwaves are becoming more frequent and may acutely increase the risk of stillbirth, a rare and severe pregnancy outcome.ObjectivesExamine the association between multiple heatwave metrics and stillbirth in six U.S. states.MethodsData were collected from fetal death and birth records in California (1996–2017), Florida (1991–2017), Georgia (1994–2017), Kansas (1991–2017), New Jersey (1991–2015), and Oregon (1991–2017). Cases were matched to controls 1:4 based on maternal race/ethnicity, maternal education, and county, and exposure windows were aligned (gestational week prior to stillbirth). County-level temperature data were obtained from Daymet and linked to cases and controls by residential county and the exposure window. Five heatwave metrics (1 categorical, 3 dichotomous, 1 continuous) were created using different combinations of the duration and intensity of hot days (mean daily temperature exceeding the county-specific 97.5th percentile) during the exposure window, as well as a continuous measure of mean temperature during the exposure window modeled using natural splines to allow for nonlinear associations. State-specific odds ratios (ORs) and 95% confidence intervals (CI) were estimated using conditional logistic regression models. State-specific results were pooled using a fixed-effects meta-analysis.ResultsIn our data set of 140,428 stillbirths (553,928 live birth controls), three of the five heatwave metrics examined were not associated with stillbirth. However, four consecutive hot days during the previous week was associated with a 3% increase in stillbirth risk (CI: 1.01, 1.06), and a 1 °C average increase over the threshold was associated with a 10% increase in stillbirth risk (CI: 1.04, 1.17). In continuous temperature analyses, there was a slight increased risk of stillbirth associated with extremely hot temperatures (≥ 35 °C).DiscussionMost heat wave definitions examined were not associated with acute changes in stillbirth risk; however, the most extreme heatwave durations and temperatures were associated with a modest increase in stillbirth risk.

The half-degree matters for heat-related health impacts under the 1.5 °C and 2 °C warming scenarios: Evidence from ambulance data in Shenzhen, China

The Paris Agreement has prompted much interest in the societal and health impacts of limiting global warming to 1.5 °C and 2 °C. Previous assessments of differential impacts of two targets indicate that 1.5 °C warming target would substantially reduce the impact on human health compared to 2 °C, but they mainly focused on the magnitude of temperature changes under future climate change scenarios without any consideration of greater frequency of cumulative heat exposures within a day. Here we quantified the health risks of compound daytime and nighttime hot extremes using morbidity data in a megacity of China, and also identified the time-period of heat exposure with higher risks. Then we projected future morbidity burden attributable to compound hot extremes due to the half-degree warming. We estimated that the 2 °C warming scenario by 2100 as opposed to 1.5 °C would increase annual heat-related ambulance dispatches by 31% in Shenzhen city. Substantial additional impacts were associated with occurrence of consecutive hot days and nights, with ambulance dispatches increased by 82%. Our results suggested that compound hot extremes should be considered in assessment of heat-related health impacts, particularly in the context of climate change. Minimizing the warming of climate in a more ambitious target can significantly reduce the health damage.

Urban heat islands and heat health warning systems in Mediterranean cities. Results from the Life ASTI project

BACKGROUND AND AIM: In the LIFE ASTI project a forecasting system for estimating the urban heat island intensity (UHI) and defining high resolution heat health watch warning systems was developed in 3 Mediterranean cities, namely Thessaloniki, Rome and Heraklion. METHODS: Mortality data and temperature data for each city were collected for the period 2013-2018. A city-specific Poisson regression model was fit to define the association between mortality and maximum apparent temperature (Tappmax) considering the following explicative variables: holidays, month (May–August), the interaction between Tappmax and month and the number of consecutive hot days above the cut-off (mean Tappmax value corresponding to all days for which excess mortality was greater than 10%). For each value of Tappmax, the model then estimates the daily excess mortality (difference between observed daily values and a baseline reference) and defines monthly thresholds and warnings levels (1,2,3). Using the LIFE ASTI high-resolution urban forecasting system (spatial resolution 250m and lead time 5 days) a differential warning is issued for each zone within the city. RESULTS:UHI forecast maps and heat warnings are issued for each city together with specific health advice to users through the Life Asti web APP (https://app.lifeasti.eu/). Forecast and observed warnings days for summer 2019-2020 were compared and associated with observed mortality data. Preliminary results on summer 2019-20 showed a slight underestimation of Tappmax values but overall a good accordance of warning days. During heat wave periods increases in mortality were observed in both Rome and Thessaloniki. The model has been adjusted and results for summer 2021 will be presented comparing forecast data with observed data from the LIFE ASTI high resolution monitoring network and mortality data. CONCLUSIONS:High resolution warnings will help activate differential public health response measures within a city and reduce heat-related effects. KEYWORDS: climate, temperature, modeling, exposures

Predictors Associated with Health-Related Heat Risk Perception of Urban Citizens in Germany.

The rising probability of extremely high temperatures and an increasing number of consecutive hot days caused by climate change—combined with the impact of these high temperatures on human health—is widely discussed in the literature. There are calls for the development of heatwave adaptation measures by governmental and scientific institutions. In this research, the predictors of health-related heat risk perception of urban citizens in Augsburg, Germany, were investigated. An online survey was conducted with 468 citizens, asking about their heat risk perception, knowledge about heat risks, and demographic data and health information. Statistical methods (Spearman correlation, unpaired t-test, ANOVA and multiple regression) were used to determine which factors were significant and relevant. The results show that the knowledge of heat risks, heat risk sensitivity and an external locus of control are the most important factors for heat risk perception. The health implication score and chronic disease show significant effects in descriptive statistics. Furthermore, younger people showed the highest heat risk perception of all age groups. Surprisingly, income, education, living alone and gender did not play a role in heat risk perception. The findings imply a need for better and intensified heat risk communication in urban areas—especially among elderly people—and thus are important for creating acceptance towards heat wave risks, which is a prerequisite of willingness to adapt.

The occurrence of heat waves in Europe and their circulation conditions

The objective of the paper was to characterize the occurrence of heat waves in Europe between 1976 and 2015 and to determine circulation conditions causing their occurrence. The heat waves were recognized as a sequence of at least 5 consecutive hot days. The hot day was defined as a day on which daily maximum air temperature was higher than 95th percentile of all the values in the analyzed period. The conducted research showed an increase in the number of heat waves and their duration in the analyzed period. The longest heat wave occurred in 2010, in Moscow, which lasted 45 days. The most intense changes were observed in the eastern and south-eastern regions. The occurrence of heat waves was mainly connected with positive anomalies of atmospheric pressure at sea level, geopotential height of 500 hPa, and temperature on isobaric surface 850 hPa.

Misfortunes never come singly: Consecutive weather shocks and mortality in Russia

This paper examines the impacts of extremely hot and cold days on mortality in Russia, using a 25-year regional panel data. Unlike other studies, the sequence of those extreme days is also taken into account, that is, the impacts of both single and consecutive (i.e. heat waves and cold spells) extreme days are estimated simultaneously. We demonstrate the importance of accounting for the sequence of extreme days. We also disentangle the impacts of those extremes by age and gender. The findings suggest that single hot days increase mortality, while single cold days do not affect mortality. On the other hand, both consecutive hot and consecutive cold days increase mortality in females and males for all age groups, although males are affected more severely. Overall, consecutive days with extreme temperatures impose considerable costs to society in terms of years of life lost. Thus, ignoring the sequences of extreme days that are likely to increase in the future because of climate change may have critical implications for mitigation policies.

Effects of heat stress in the leaf mitotic cell cycle and chromosomes of four wine-producing grapevine varieties.

Grapevine varieties respond differentially to heat stress (HS). HS ultimately reduces the photosynthesis and respiratory performance. However, the HS effects in the leaf nuclei and mitotic cells of grapevine are barely known. This work intends to evaluate the HS effects in the leaf mitotic cell cycle and chromosomes of four wine-producing varieties: Touriga Franca (TF), Touriga Nacional (TN), Rabigato, and Viosinho. In vitro plants with 11months were used in a stepwise acclimation and recovery (SAR) experimental setup comprising different phases: heat acclimation period (3h-32°C), extreme HS (1h-42°C), and two recovery periods (3h-32°C and 24h-25°C), and compared to control plants (maintained in vitro at 25°C). At the end of each SAR phase, leaves were collected, fixed, and used for cell suspensions and chromosome preparations. Normal and abnormal interphase and mitotic cells were observed, scored, and statistically analyzed in all varieties and treatments (control and SAR phases). Different types of chromosomal anomalies in all mitotic phases, treatments, and varieties were found. In all varieties, the percentage of dividing cells with anomalies (%DCA) after extreme HS increased relative to control. TF and Viosinho were considered the most tolerant to HS. TF showed a gradual MI reduction from heat acclimation to HS and the lowest %DCA after HS and 24h of recovery. Only Viosinho reached the control values after the long recovery period. Extrapolating these data to the field, we hypothesize that during consecutive hot summer days, the grapevine plants will not have time or capacity to recover from the mitotic anomalies caused by high temperatures.

Thermal Conditions in the City of Poznań (Poland) during Selected Heat Waves

The aim of the study was to characterise the occurrence of hot days and heat waves in Poznań in the 1966–2015 period, as well as to describe the thermal conditions in the city during selected heat waves between 2008 and 2015. The basis of the study was the daily maximum and minimum air temperature values for Poznań–Ławica station from 1966–2015 and the daily values of air temperature from eight measuring points located in the city in various land types from 2008 to 2015. A hot day was defined as a day with Tmax above the 95th annual percentile (from 1966 to 2015), while a heat wave was assumed to be at least five consecutive hot days. The research study conducted shows the increase of Tmax, number of hot days and frequency of heat waves in Poznań over the last 50 years. Across the area of the city (differentiation of urban area types according to Urban Atlas 2012), there was a great diversity of thermal conditions during the heat waves analysed.

The impact of sustained hot weather on risk of acute work-related injury in Melbourne, Australia.

It has been reported that weather-related high ambient temperature is associated with an increased risk of work-related injury. Understanding this relationship is important because work-related injuries are a major public health problem, and because projected climate changes will potentially expose workers to hot days, including consecutive hot days, more often. The aim of this study was to quantify the impact of exposure to sustained periods of hot weather on work-related injury risk for workers in Melbourne, Australia. A time-stratified case crossover study design was utilised to examine the association between two and three consecutive days and two and three consecutive nights of hot weather and the risk of work-related injury, using definitions of hot weather ranging from the 60th to the 95th percentile of daily maximum and minimum temperatures for the Melbourne metropolitan area, 2002-2012. Workers' compensation claim data was used to identify cases of acute work-related injury. Overall, two and three consecutive days of hot weather were associated with an increased risk of injury, with this effect becoming apparent at a daily maximum temperature of 27.6°C (70th percentile). Three consecutive days of high but not extreme temperatures were associated with the strongest effect, with a 15% increased risk of injury (odds ratio 1.15, 95% confidence interval 1.01-1.30) observed when daily maximum temperature was ≥33.3°C (90th percentile) for three consecutive days, compared to when it was not. At a threshold of 35.5°C (95th percentile), there was no significant association between temperature and injury for either two or three consecutive days of heat. These findings suggest that warnings to minimise harm to workers from hot weather should be given, and prevention protocol initiated, when consecutive warm days of temperatures lower than extreme heat temperatures are forecast, and well before the upper ranges of ambient daytime temperatures are reached.

Humid heat waves at different warming levels

The co-occurrence of consecutive hot and humid days during a heat wave can strongly affect human health. Here, we quantify humid heat wave hazard in the recent past and at different levels of global warming. We find that the magnitude and apparent temperature peak of heat waves, such as the ones observed in Chicago in 1995 and China in 2003, have been strongly amplified by humidity. Climate model projections suggest that the percentage of area where heat wave magnitude and peak are amplified by humidity increases with increasing warming levels. Considering the effect of humidity at 1.5° and 2° global warming, highly populated regions, such as the Eastern US and China, could experience heat waves with magnitude greater than the one in Russia in 2010 (the most severe of the present era). The apparent temperature peak during such humid-heat waves can be greater than 55 °C. According to the US Weather Service, at this temperature humans are very likely to suffer from heat strokes. Humid-heat waves with these conditions were never exceeded in the present climate, but are expected to occur every other year at 4° global warming. This calls for respective adaptation measures in some key regions of the world along with international climate change mitigation efforts.

Characterizing prolonged heat effects on mortality in a sub-tropical high-density city, Hong Kong

Extreme hot weather events are likely to increase under future climate change, and it is exacerbated in urban areas due to the complex urban settings. It causes excess mortality due to prolonged exposure to such extreme heat. However, there is lack of universal definition of prolonged heat or heat wave, which leads to inadequacies of associated risk preparedness. Previous studies focused on estimating temperature-mortality relationship based on temperature thresholds for assessing heat-related health risks but only several studies investigated the association between types of prolonged heat and excess mortality. However, most studies focused on one or a few isolated heat waves, which cannot demonstrate typical scenarios that population has experienced. In addition, there are limited studies on the difference between daytime and nighttime temperature, resulting in insufficiency to conclude the effect of prolonged heat. In sub-tropical high-density cities where prolonged heat is common in summer, it is important to obtain a comprehensive understanding of prolonged heat for a complete assessment of heat-related health risks. In this study, six types of prolonged heat were examined by using a time-stratified analysis. We found that more consecutive hot nights contribute to higher mortality risk while the number of consecutive hot days does not have significant association with excess mortality. For a day after five consecutive hot nights, there were 7.99% [7.64%, 8.35%], 7.74% [6.93%, 8.55%], and 8.14% [7.38%, 8.88%] increases in all-cause, cardiovascular, and respiratory mortality, respectively. Non-consecutive hot days or nights are also found to contribute to short-term mortality risk. For a 7-day-period with at least five non-consecutive hot days and nights, there was 15.61% [14.52%, 16.70%] increase in all-cause mortality at lag 0-1, but only -2.00% [-2.83%, -1.17%] at lag 2-3. Differences in the temperature-mortality relationship caused by hot days and hot nights imply the need to categorize prolonged heat for public health surveillance. Findings also contribute to potential improvement to existing heat-health warning system.

The Urban Heat Island Effect in the City of Valencia: A Case Study for Hot Summer Days

Extreme heat poses significant risks to the world’s growing urban population, and the heat stress to human health is likely to escalate with the anthropogenically increased temperatures projected by climate models. Thus, the additional heat from the urban heat island (UHI) effect needs to be quantified, including the spatial pattern. This study focuses on the city of Valencia (Spain), investigating the intensity and spatial pattern of UHI during three consecutive hot summer days accompanying a heat record. For the analysis, long-term in situ measurements and remote sensing data were combined. The UHI effect was evaluated using two approaches: (a) based on air temperature (AT) time-series from two meteorological stations and (b) using land surface temperature (LST) images from MODIS products by NASA with 1 km resolution. The strongest nighttime UHI estimated from AT was 2.3 °C, while the most intense surface UHI calculated as the difference between the LST of urban and rural regions (defined by NDVI) was 2.6 °C—both measured during the night after the record hot day. To assess the human thermal comfort in the city the Discomfort Index was applied. With the increasing number of tropical nights, the mitigation of nighttime UHI is a pressing issue that should be taken into consideration in climate-resilient urban planning.

Effect of heat waves on embryo mortality in the pine processionary moth.

Extreme climate events such as heat waves are predicted to become more frequent with climate change, representing a challenge for many organisms. The pine processionary moth Thaumetopoea pityocampa is a Mediterranean pine defoliator, which typically lays eggs during the summer. We evaluated the effects of heat waves on egg mortality of three populations with different phenologies: a Portuguese population with a classical life cycle (eggs laid in summer), an allochronic Portuguese population reproducing in spring, and a Tunisian population from the extreme southern limit of T. pityocampa distribution range, in which eggs are laid in fall. We tested the influence of three consecutive hot days on egg survival and development time, using either constant (CT) or daily cycling temperatures (DT) with equivalent mean temperatures. Maximum temperatures (T max) used in the experiment ranged from 36 to 48°C for DT and from 30 to 42°C for CT. Heat waves had a severe negative effect on egg survival when T max reached 42°C for all populations. No embryo survived above this threshold. At high mean temperatures (40°C), significant differences were observed between populations and between DT and CT regimes. Heat waves further increased embryo development time. The knowledge we gained about the upper lethal temperature to embryos of this species will permit better prediction of the potential expansion of this insect under different climate warming scenarios.

Distribution and trend on consecutive days of severe weathers in China during 1959–2014

Based on daily surface climate data and weather phenomenon data, the spatial and temporal distribution and trend on the number of consecutive days of severe weathers were analyzed in China during 1959–2014. The results indicate that the number of consecutive days for hot weathers increased at a rate of 0.1 day per decade in China as a whole, while that for cold weathers, snowfall weathers, thunderstorm weathers and foggy weathers showed significant decreasing trends at rates of 1.4, 0.3, 0.4 and 0.4 day per decade, respectively. Spatially, there were more consecutive hot days and rainstorm days in southeastern China, and more consecutive cold days and snowfall days in northeastern China and western China. Consecutive thunderstorm days were more in southern China and southwestern China, and consecutive foggy days were more in some mountain stations. Over the past 56 years, annual number of consecutive cold days decreased mainly in most parts of western China and eastern China. Consecutive thunderstorm days decreased in most parts of China. The trend of consecutive hot days, snowfall days and foggy days was not significant in most parts of China, and that of consecutive rainstorm days was not significant in almost the entire China.

景德镇市异常高温的分析与预报

本文统计分析了景德镇市1953~2013年异常高温的气候特点及天气形势、本站要素等特点，提出了预报指标，归纳了天气学概念模型。主要结论如下：1) 38℃以上高温天气平均每年有3.3天，最多28天，有23年未出现38℃以上的高温天气，占总数的37.7%。大约9~10年内会有一个较为炎热的年份。异常高温绝大部分均出现在7~9月，40℃以上高温天气非常稀少，每8年才会出现1次。2) 异常高温常连续出现，连续2天出现的共有45个过程，年均0.74个；连续3天出现的共有26个过程，年均0.43个；大致每10年会有一次连续5天或以上持续38℃或以上的高温天气过程。3) 造成景德镇市异常高温的天气形势绝大部分是在强大的副热带高压控制下发生的，其余可分为台风西北侧型、台风西侧型、台风北侧型和西北气流型等4种形势。4) 建立的概念模型显示，河套以南的我国东部地区为强盛的副热带高压控制，850 hPa在长江下游至入海口和湖北北部地区有24℃或以上的暖中心，景德镇位于暖中心以南的22℃等温线附近。850 hPaTd > 16℃线位于江西东部与浙江、福建的交界处，在江西北部~浙江大部500 hPa有T-Td > 20℃的干舌，干舌位于低层暖中心东南部，景德镇位于高层干舌与低层露点高值区的交界处。 In this article, climate characteristic and weather pattern have been analyzed, and synoptic model is also induced. Main conclusions are as following: 1) An average level of 38˚C or above is 3.3 days per year and tops at 28. Totally, there are 23 years that abnormal high temperature days have never shown up, making up 37.7% of all the 61 years. A hot year occurs almost once every 9 to 10 years and most high temperature appears between July and September. 40˚C-above days are very rare, which happens once every 8 years. 2) Abnormal high temperature days are always consecu-tive. There are totally 45 processes of 2 consecutive hot days and 26 processes of 3 consecutive hot days, making up average days of 0.74 and 0.43 per year. Once every 10 years, there would be a 38˚C-above process lasting 5 days or more. 3) The weather pattern that induces abnormal high temperature usually shows as under the control of a strong subtropical anticyclone, while the rest could be divided as the north-west typhoon pattern, west typhoon pattern, north typhoon pattern and north-west stream pattern. 4) The synoptic model shows the areas of east China at the south of Hetao are controlled by strong subtropical anticyclone and there exists a warm center of 24˚C or above at the lower Yangtze River and north Hubei province on 850 hPa while Jingdezhen locates at 22˚C isotherm in the south of the center. Td > 16˚C area locates at the east Jiangxi and the border of Zhejiang and Fujian on 850 hPa while on 500hPa exists a dry tongue of T-Td > 20˚C at the north of Jiangxi and Zhejiang. This dry tongue locates at the southeast part of the low level warm center and Jingdezhen is right on the border of the dry tongue in the high level and the high Td area in the low level.

Changes in thermal extremes in Poland

Changes in thermal extremes of the climate of Poland in 1951–2010 are examined. Warm extremes have become more frequent, while cold extremes have become less frequent. In the warming climate of Poland, the increase in the number of extremely warm days in a year and the decrease in the number of extremely cold days in a year have been observed. Also the increase of the maximum number of consecutive hot days in a year and the decrease of the maximum number of consecutive very cold and extremely cold days in a year have been observed. However, the trends are not of ubiquitous statistic significance, as the natural variability is strong.

Modeling complex systems in the geosciences

Many geophysical phenomena can be described as complex systems, involving phenomena such as extreme or “wild” events that often do not follow the Gaussian distribution that would be expected if the events were simply random and uncorrelated. For instance, some geophysical phenomena like earthquakes show a much higher occurrence of relatively large values than would a Gaussian distribution and so are examples of the “Noah effect” (named by Benoit Mandelbrot for the exceptionally heavy rain in the biblical flood). Other geophysical phenomena are examples of the “Joseph effect,” in which a state is especially persistent, such as a spell of multiple consecutive hot days (heat waves) or several dry summers in a row. The Joseph effect was named after the biblical story in which Joseph's dream of seven fat cows and seven thin ones predicted 7 years of plenty followed by 7 years of drought.

Differences on the effect of heat waves on mortality by sociodemographic and urban landscape characteristics

BackgroundMortality increases during heat waves have been reported worldwide. The magnitude of these increases can vary within regions according to sociodemographic and urban landscape characteristics. The objectives of this study...