Extreme Hot Events Research Articles

Spatiotemporal analysis of regional socio-economic vulnerability change associated with heat risks in Canada

Excess mortality can be caused by extreme hot weather events, which are increasing in severity and frequency in Canada due to climate change. Individual and social vulnerability factors influence the mortality risk associated with a given heat exposure. We constructed heat vulnerability indices using census data from 2006 to 2011 in Canada, developed a novel design to compare spatiotemporal changes of heat vulnerability, and identified locations that may be increasingly vulnerable to heat. The results suggest that 1) urban areas in Canada are particularly vulnerable to heat, 2) suburban areas and satellite cities around major metropolitan areas show the greatest increases in vulnerability, and 3) heat vulnerability changes are driven primarily by changes in the density of older ages and infants. Our approach is applicable to heat vulnerability analyses in other countries.

Time‐sensitive analysis of a warming climate on heat waves in Saudi Arabia: Temporal patterns and trends

The climate of the Middle East is warming and extreme hot temperature events are becoming common, as observed by the significant upwards trends in mean and extreme temperatures during the last few decades. Climate modelling studies suggest that the frequency, intensity, and duration of extreme temperature events are expected to increase as the global and local climate continues to warm. However, most of the literature about heat waves (HWs) in Saudi Arabia provides information about the duration aspect using a single index, with no detailed information about frequency and intensity aspects. To help establish a baseline for understanding past and future change, this study explored the temporal behaviour(s) of the frequency, duration, and intensity of HWs in Saudi Arabia under the observed recent climate change. Several issues are addressed including some methodological concerns associated with the commonly used heat wave index, data quality control, and statistical analysis. A new definition and method to detect HWs and their changes is proposed, considering the ongoing effects of climate warming and the subtropical arid climate.A HW event is defined as a period of two or more consecutive days (i.e., at least 48 hr) with a daily maximum and minimum temperature exceeding the 90th and 85th percentiles of the maximum and minimum, respectively. Threshold percentiles were calculated monthly and adjusted for each decade of analysis. For temporal trend analyses, we consider HW events and their duration as count data using different Poisson models for analysis. HW frequency, intensity, and duration across Saudi Arabia were found to behave geographically and temporally differently across the 25 stations studied. Distinct temporal and geographical patterns were observed indicating a confounding interplay of regional and local factors, such as urbanization, elevation, latitude, and distance from a large body of water.

The Heat Exposure Integrated Deprivation Index (HEIDI): A Data-Driven Approach to Mapping Extreme Hot Weather Risk

Background/Aim: Extreme hot weather events are increasing in intensity, frequency, and duration as a consequence of climate change. As a result, hot weather mortality is a growing concern in many u...

Evaluating the variability and trends in extreme climate events in the Kashmir Valley using PRECIS RCM simulations

Climate is the major force that shapes the Earth. Under climate change conditions, the extreme events shall occur more frequently with greater force for devastation. In this study, Predicting Regional climate for impact studies-Regional climate model (PRECIS RCM) was used to analyze the trends in temperature and precipitation using climate indices for the Kashmir valley, western Himalaya. We analyzed 27 climate extremity indices using PRECIS RCM simulations for a baseline (1961–1990) and future scenario (1990–2098) using RCLIMDEX model. Trend analysis was carried out using Mann–Kendall test method and Theil-Sen estimator. PRECIS RCM covers Kashmir valley in 14 grids of 50 km × 50 km horizontal resolution each. The climatic grids for baseline data (1961–1990) indicated no noteworthy patterns in hot and cold extreme indices. However, climate grids for future simulations (1990–2098) showed an increasing trend in all hot extreme events but no significant trend in cold extremes. The futuristic frequency and intensity in the extreme temperature events showed significant increase compared to extreme precipitation events. The overall results indicated that grids pertaining to valley plains shall have more extreme events in maximum temperatures while as the grids towards the mountain fronts shall have more extreme events in precipitation and minimum temperatures in the future. The results establish a strong link between changing climate and climatic extremes in the region. The study is finally aimed to use PRECIS RCM simulations for impact assessment studies in the region.

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.

Interdecadal variability of the large-scale extreme hot event frequency over the middle and lower reaches of the Yangtze River basin and its related atmospheric patterns

Based on daily maximum temperature data from Chinese weather stations for the period 1960–2013, the characteristics of the interdecadal variability of large-scale extreme hot event (EHE) frequency ...

A proposed case-control framework to probabilistically classify individual deaths as expected or excess during extreme hot weather events.

BackgroundMost excess deaths that occur during extreme hot weather events do not have natural heat recorded as an underlying or contributing cause. This study aims to identify the specific individuals who died because of hot weather using only secondary data. A novel approach was developed in which the expected number of deaths was repeatedly sampled from all deaths that occurred during a hot weather event, and compared with deaths during a control period. The deaths were compared with respect to five factors known to be associated with hot weather mortality. Individuals were ranked by their presence in significant models over 100 trials of 10,000 repetitions. Those with the highest rankings were identified as probable excess deaths. Sensitivity analyses were performed on a range of model combinations. These methods were applied to a 2009 hot weather event in greater Vancouver, Canada.ResultsThe excess deaths identified were sensitive to differences in model combinations, particularly between univariate and multivariate approaches. One multivariate and one univariate combination were chosen as the best models for further analyses. The individuals identified by multiple combinations suggest that marginalized populations in greater Vancouver are at higher risk of death during hot weather.ConclusionsThis study proposes novel methods for classifying specific deaths as expected or excess during a hot weather event. Further work is needed to evaluate performance of the methods in simulation studies and against clinically identified cases. If confirmed, these methods could be applied to a wide range of populations and events of interest.

The relationship between neighbourhood tree canopy cover and heat-related ambulance calls during extreme heat events in Toronto, Canada

Two thirds of Canadians reside in urban areas and 85% of recent population growth occurs in these areas. The intensity and duration of extreme hot weather events are predicted to increase in Canadian cities and in cities globally. It is well established that human suffering due to extreme heat is exacerbated in urban as compared to rural environments. Understanding the characteristics of urban landscapes that play the greatest roles in exacerbating the human health impact of extreme heat is thus imperative. This study explores the relationship between the amount of canopy cover from trees and the incidence of heat-related morbidity during extreme heat events in 544 neighbourhoods of Toronto, Ontario, Canada. Four extreme heat events from three years were studied. Heat-related ambulance calls were found to be 12.3% higher during the heat events than in the preceding or the following week. The number of heat-related ambulance calls was negatively correlated to canopy cover (Spearman Rank rho=−0.094, p=0.029) and positively correlated to hard surface cover (Spearman Rank rho=0.150, p<0.001). Toronto neighbourhoods, as defined by Census Tracts, with less than 5% canopy cover had approximately five times as many heat-related calls as those with greater than 5% tree canopy cover, and nearly fifteen times as many heat-related calls as Census Tracts with greater than 70% tree canopy cover. These data suggest that even a marginal increase in the tree canopy cover from <5% to >5% could reduce heat-related ambulance calls by approximately 80%. These results have important implications for human health during heat events, particularly in the context of global climate change and urban heat islands, both of which are trending toward hotter urban environments in future.

Effective monitoring and warning of Urban Heat Island effect on the indoor thermal risk in Bucharest (Romania)

Extreme hot events and heat waves occur frequently in Bucharest during the warm season, triggering significant heat stress and thermal risks, especially in buildings with inappropriate ventilation, while climate change scenarios agree upon the warming trend along the next decades. This study investigates the impact of the Urban Heat Island (UHI) on the thermal regime of buildings, in order to develop a warning system capable to issue early warnings when the thermal risk reaches high levels in Bucharest. The warnings should be accurate regarding the intensity of the risk, the temporal fit and location, and complex information is compiled (e.g. air and land surface temperature, land cover, buildings and flat characteristics). Ground-based meteorological data and satellite products were used for computing the ambient temperature over several test areas for the summer months, and the indoor climate was dynamically modelled with an hourly resolution. The thermal risk was determined using standardized comfort indices, e.g. Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD), and the specific thermal and functional characteristics of the buildings.

Analyses of Observed and Anticipated Changes in Extreme Climate Events in the Northwest Himalaya

In this study, past (1970-2005) as well as future long term (2011-2099) trends in various extreme events of temperature and precipitation have been investigated over selected hydro-meteorological stations in the Sutlej river basin. The ensembles of two Coupled Model Intercomparison Project (CMIP3) models: third generation Canadian Coupled Global Climate Model and Hadley Centre Coupled Model have been used for simulation of future daily time series of temperature (maximum and minimum) and precipitation under A2 emission scenario. Large scale atmospheric variables of both models and National Centre for Environmental Prediction/National Centre for Atmospheric Research reanalysis data sets have been downscaled using statistical downscaling technique at individual stations. A total number of 25 extreme indices of temperature (14) and precipitation (11) as specified by the Expert Team of the World Meteorological Organization and Climate Variability and Predictability are derived for the past and future periods. Trends in extreme indices are detected over time using the modified Mann-Kendall test method. The stations which have shown either decrease or no change in hot extreme events (i.e., maximum TMax, warm days, warm nights, maximum TMin, tropical nights, summer days and warm spell duration indicators) for 1970–2005 and increase in cold extreme events (cool days, cool nights, frost days and cold spell duration indicators) are predicted to increase and decrease respectively in the future. In addition, an increase in frequency and intensity of extreme precipitation events is also predicted.

Recent spatiotemporal patterns in temperature extremes across conterminous United States

AbstractWith a warming climate, understanding the physical dynamics of hot and cold extreme events has taken on increased importance for public health, infrastructure, ecosystems, food security, and other domains. Here we use a high‐resolution spatial and temporal seamless gridded land surface forcing data set to provide an assessment of recent spatiotemporal patterns in temperature extremes over the conterminous United States (CONUS). We asked the following: (1) How are temperature extremes changing across the different regions of CONUS? (2) How do changes in extremes vary on seasonal, annual, and decadal scales? (3) How do changes in extremes relate to changes in mean conditions? And (4) do extremes relate to major modes of ocean‐atmosphere variability? We derive a subset of the CLIMDEX extreme indices from the North American Land Data Assimilation phase 2 forcing data set. While there were warming trends in all indices, daytime temperature extremes warmed more than nighttime. Spring warming was the strongest and most extensive across CONUS, and summer experienced the strongest and most extensive decrease in cold extremes. Increase in winter warm extremes appeared weakening relative to the rapid 1950–1990 increase found in previous studies. The Northeast and Midwest experienced the most warming, while the Northwest and North Great Plains saw the least. We found changes in average temperatures were more associated with changes in cold extremes than warm extremes. Since 2006 there have been 5 years when more than 5% of the U.S. experienced at least 90 warm days, something not observed in the previous 25 years. The unusually warm first decade of 21st century could have been associated with the warm conditions of near El Niño–Southern Oscillation‐neutral phase of the decade, and possibly amplified by anthropogenic forcing. The widespread, lengthy, and severe extreme hot events documented here during the past three decades underscore the need to implement thoughtful adaptation plans in the very near future, to the growing evidence of increasing warm extremes across United States.

Projected changes to high temperature events for Canada based on a regional climate model ensemble

Extreme hot spells can have significant impacts on human society and ecosystems, and therefore it is important to assess how these extreme events will evolve in a changing climate. In this study, the impact of climate change on hot days, hot spells, and heat waves, over 10 climatic regions covering Canada, based on 11 regional climate model (RCM) simulations from the North American Regional Climate Change Assessment Program for the June to August summer period is presented. These simulations were produced with six RCMs driven by four Atmosphere–Ocean General Circulation Models (AOGCM), for the A2 emission scenario, for the current 1970–1999 and future 2040–2069 periods. Two types of hot days, namely HD-1 and HD-2, defined respectively as days with only daily maximum temperature (Tmax) and both Tmax and daily minimum temperature (Tmin) exceeding their respective thresholds (i.e., period-of-record 90th percentile of Tmax and Tmin values), are considered in the study. Analogous to these hot days, two types of hot spells, namely HS-1 and HS-2, are identified as spells of consecutive HD-1 and HD-2 type hot days. In the study, heat waves are defined as periods of three or more consecutive days, with Tmax above 32 °C threshold. Results suggest future increases in the number of both types of hot days and hot spell events for the 10 climatic regions considered. However, the projected changes show high spatial variability and are highly dependent on the RCM and driving AOGCM combination. Extreme hot spell events such as HS-2 type hot spells of longer duration are expected to experience relatively larger increases compared to hot spells of moderate duration, implying considerable heat related environmental and health risks. Regionally, the Great Lakes, West Coast, Northern Plains, and Maritimes regions are found to be more affected due to increases in the frequency and severity of hot spells and/or heat wave characteristics, requiring more in depth studies for these regions to facilitate appropriate adaptation measures.

Anthropogenic contribution to global occurrence of heavy-precipitation and high-temperature extremes

The contribution of human-induced climate change to global heavy precipitation and hot extreme events is quantified. The results show that of the moderate extremes, 18% of precipitation and 75% of high-temperature events are attributable to warming.

A Proposed Resampling Method to Separate Excess Deaths from Expected Deaths during Extreme Hot Weather Events

*Introduction:* Most excess deaths that occur during extreme hot weather events do not have natural heat recorded as an underlying or contributing cause. This makes it challenging to identify excess deaths from administrative databases, but such information could improve epidemiologic study and public health protection. We describe a resampling approach in a case-control framework designed to classify all deaths during an event as probable expected or probable excess, and we apply the approach to a 2009 event in Vancouver, Canada. Methods:* The underlying assumption is that deaths expected during a hot weather are similar to deaths that occur during typical summer weather with respect to characteristics of the decedents. As such, case-control analyses comparing expected hot weather deaths with typical weather deaths should be null for variables associated with hot weather mortality. We sampled the number of expected deaths from the pool of all hot weather deaths 50,000 times to identify decedents who were consistently included in non-null analyses on age, location of death, deprivation, population density, and local greenness. Results:* Mean age for the most probable excess deaths was 14.5 years younger than that for controls, 47% died in the community, 52% lived in deprived neighborhoods, 67% lived in densely populated areas, and there was 36% less greenness around their residences. Underlying cause of death indicated that 20% were attributed to external causes, predominantly accidental overdoses, intentional overdoses, and other forms of self harm. *Discussion:* As the global climate changes we expect more frequent and intense periods of extreme hot weather. The proposed method can be used with readily available administrative data to rapidly assess excess mortality following such events. This example has provided further evidence for improved emergency response in Vancouver following the 2009 event.

Influences of the Antarctic Ozone Hole on Southern Hemispheric Summer Climate Change

Abstract Over the past three decades, Antarctic surface climate has undergone pronounced changes. Many of these changes have been linked to stratospheric ozone depletion. Here linkages between Antarctic ozone loss, the accompanying circulation changes, and summertime Southern Hemisphere (SH) midlatitude surface temperatures are explored. Long-term surface climate changes associated with ozone-driven changes in the southern annular mode (SAM) at SH midlatitudes in summer are not annular in appearance owing to differences in regional circulation and precipitation impacts. Both station and reanalysis data indicate a trend toward cooler summer temperatures over southeast and south-central Australia and inland areas of the southern tip of Africa. It is also found that since the onset of the ozone hole, there have been significant shifts in the distributions of both the seasonal mean and daily maximum summertime temperatures in the SH midlatitude regions between high and low ozone years. Unusually hot summer extremes are associated with anomalously high ozone in the previous November, including the recent very hot austral summer of 2012/13. If the relationship found in the past three decades continues to hold, the level of late springtime ozone over Antarctica has the potential to be part of a useful predictor set for the following summer’s conditions. The results herein suggest that skillful predictions may be feasible for both the mean seasonal temperature and the frequency of extreme hot events in some SH midlatitude regions of Australia, Africa, and South America.

Record-breaking SST over mid-North Atlantic and extreme high temperature over the Jianghuai–Jiangnan region of China in 2013

In July 2013, the Jianghuai–Jiangnan region of China experienced a persistent extreme high temperature, and the surface air temperature (SAT) over many areas of the region set a new record, which had a profound impact on people’s lives. This study explored the possible mechanism for this extreme climate phenomenon. The results show that the sea surface temperature (SST) over the mid-North Atlantic in July 2013 was the warmest observed over the past 160 years. The strong anomaly of the SST connects to the East Asian upper level westerly and western Pacific subtropical high (WPSH) via the teleconnection wave train and further contributes to the SAT variability over the Jianghuai–Jiangnan region; this connection could be one possible mechanism for the formation of the record-breaking extreme hot event (EHE) over the Jianghuai–Jiangnan region in July 2013. In addition, for the EHE over the Jianghuai–Jiangnan region, the role of the WPSH was generally emphasised. This study found that the variability of the upper level westerly over the Jianghuai–Jiangnan region is also an important climate factor impacting the SAT of the region. In particular, the record-breaking weakness of the upper level westerly corresponded to the record-breaking SAT over the Jianghuai–Jiangnan region in July 2013. These results indicate that the role of the upper level westerly should be emphasised in addition to the WPSH, according to both the variability in the summer air temperature and the EHE over the Jianghuai–Jiangnan region.

Climate Change Hotspots Identification in China through the CMIP5 Global Climate Model Ensemble

China is one of the countries vulnerable to adverse climate changes. The potential climate change hotspots in China throughout the 21st century are identified in this study by using a multimodel, multiscenario climate model ensemble that includes Phase Five of the Coupled Model Intercomparison Project (CMIP5) atmosphere-ocean general circulation models. Both high (RCP8.5) and low (RCP4.5) greenhouse gas emission trajectories are tested, and both the mean and extreme seasonal temperature and precipitation are considered in identifying regional climate change hotspots. Tarim basin and Tibetan Plateau in West China are identified as persistent regional climate change hotspots in both the RCP4.5 and RCP8.5 scenarios. The aggregate impacts of climate change increase throughout the 21st century and are more significant in RCP8.5 than in RCP4.5. Extreme hot event and mean temperature are two climate variables that greatly contribute to the hotspots calculation in all regions. The contribution of other climate variables exhibits a notable subregional variability. South China is identified as another hotspot based on the change of extreme dry event, especially in SON and DJF, which indicates that such event will frequently occur in the future. Our results can contribute to the designing of national and cross-national adaptation and mitigation policies.

Possible Impact of the Summer North Atlantic Oscillation on Extreme Hot Events in China

AbstractThis paper reveals that the summer North Atlantic Oscillation (SNAO) is closely related to the extreme hot event (EHE) variability in China during the period of 1979-2009, with a positive-phase (negative-phase) SNAO corresponding to less (more) EHEs in northern China. The summer circulation anomalies associated with the SNAO give further confirmation of the above relationship. In a positive-phase (negative-phase) SNAO year, there is an anomalous cyclone (anticyclone) over central East Asia, which can increase (decrease) the total cloud cover over this region. Such changes of the total cloud cover can then decrease (increase) the solar radiation reaching the surface, which is consequently un-favorable (favorable) to the formation of EHEs over northern China.

A new approach for the definition of extreme anomalous hot and dry weather events in Israel

Se analizan eventos anómalos extremos de tiempo cálido y seco en Israel basado en una nuevadefinición para tales eventos. Se proponen cuatro umbrales de condiciones extremas climáticas cálidasy secas. En este sentido, un día anómalo extremo caliente y seco se define cuando se cumplen doscondiciones: La puntuación estándar de la temperatura está por encima de uno de los cuatro umbralesy la puntuación estándar de la humedad relativa es inferior a uno de los cuatro umbrales. La conclusiónprincipal de este estudio es que las diferencias de temperatura y humedad relativa en diversas regionesgeográficas requieren una nueva definición para anomalía extrema de clima cálido y seco basado enuna base regional y no en uno único para todo el país a través del año. Mediante el establecimiento devarios grados de eventos extremos anómalos de clima cálido y seco y en base a la media mensual y ladesviación estándar de los valores de temperatura máxima y mínima y los valores de humedad relativapara cada región, se puede obtener una definición más precisa de tales eventos. Este enfoque puede serutilizado en todo el mundo y pueden servir para analizar posibles cambios climáticos.

Impacts of extreme air temperatures on cyanobacteria in five deep peri-Alpine lakes

Cyanobacteria are of major interest in freshwater ecosystems, since they are able to produce toxins with potentially negative impacts on the environment, health and thus on economics and society. It is therefore important for water management authorities to assess the manner in which cyanobacteria may evolve under climate change, especially in the Alpine Region where warming is projected by climate models to be more important than the global average. In this study, air temperature extremes under current climate were used as a proxy for future average climate forced by enhanced greenhouse gas concentrations. The impacts of extreme temperature events on cyanobacteria were analyzed in five deep peri-Alpine lakes, covering the entire trophic gradient and using a synoptic approach. Extreme air temperatures were observed to alter the biomass of the cyanobacteria community. In general, extreme hot events are associated with high biomass while extreme cold events are characterised by low biomass. However, the assessed air temperature extremes did not lead to a dominance of cyanobacteria over the other phytoplankton groups, which also showed responses in relative biomass change during extreme events. Both extreme hot and extreme cold events were seen to generate a loss of diversity among cyanobacteria. In addition, the use of extreme events as a proxy to average future climates is a useful approach to enhance possible impacts of future global warming on the biota in freshwater systems. The outcomes of a synoptic approach provide general responses and are a useful tool for further modelling purposes.