Summer Heat Waves Research Articles

Amplified seasonality in western Europe in a warmer world.

Documenting the seasonal temperature cycle constitutes an essential step toward mitigating risks associated with extreme weather events in a future warmer world. The mid-Piacenzian Warm Period (mPWP), 3.3 to 3.0 million years ago, featured global temperatures approximately 3°C above preindustrial levels. It represents an ideal period for directed paleoclimate reconstructions equivalent to model projections for 2100 under moderate Shared Socioeconomic Pathway SSP2-4.5. Here, seasonal clumped isotope analyses of fossil mollusk shells from the North Sea are presented to test Pliocene Model Intercomparison Project 2 outcomes. Joint data and model evidence reveals enhanced summer warming (+4.3° ± 1.0°C) compared to winter (+2.5° ± 1.5°C) during the mPWP, equivalent to SSP2-4.5 outcomes for future climate. We show that Arctic amplification of global warming weakens mid-latitude summer circulation while intensifying seasonal contrast in temperature and precipitation, leading to an increased risk of summer heat waves and other extreme weather events in Europe's future.

Assessment of subjective well-being of healthcare workers in response to heat and personal protective equipment under controlled conditions using a standardized protocol

BackgroundDue to climate change, the increasing frequency of hot summer days and heat waves can result in occupational heat strain, especially in non-air-conditioned workplaces. Healthcare workers (HCW) engaged in patient care are particularly affected, as they are additionally exposed to physical stress. The use of personal protective equipment (PPE) can aggravate heat strain in HCW. This study aimed to examine the subjective well-being of HCW when exposed to heat and PPE under controlled conditions.MethodsThis study was designed as a randomized crossover trial. Participants performed standardized healthcare tasks in a climatic chamber for approximately 3.5 h at different indoor temperatures (22 °C and 27 °C) and varied working conditions (with or without PPE). The effects on participants’ subjective well-being, encompassing thermal, physiological and psychological stress were assessed using a customized questionnaire.ResultsHeat had a greater effect than PPE on thermal, physical and psychological stress. Conversely, PPE had a greater effect on physical demand and effort. For the majority of outcomes, combined exposure to heat and PPE resulted in the highest perceived discomfort. Furthermore, the participants reported increased sweating and other discomforts when working at elevated temperatures or with PPE.ConclusionsIn this study, heat and PPE, but particularly the combination of both factors, were identified as unfavorable working environments. Although the trials were conducted in a controlled environment, the outcomes provide valuable information about the effect of heat and PPE on HCW in a real-life setting. Furthermore, the design used in this study can be beneficial in evaluating the effect of mitigation strategies.

Preconditioning of mountain permafrost towards degradation detected by electrical resistivity

Warming permafrost has been detected worldwide and is projected to continue during the next century by many modelling studies. In mountain regions, this can lead to potentially hazardous impacts on short time-scales by an increased tendency for slope instabilities. However, time scales of permafrost thaw and the role of the ice content are less clear, especially in heterogeneous mountain terrain, where ice content can vary between zero and supersaturated conditions over small distances. Warming of permafrost near the freezing point shows therefore complex inter-annual behaviour due to latent heat effects during thawing and the influence of the snow-cover, which is governed by highly non-linear processes itself. Here, we demonstrate a preconditioning effect within near-surface layers in mountain permafrost that causes non-linear degradation and accelerates thaw. We hypothesise that a summer heat wave, as has occurred in the Central European summers 2003, 2015 and 2022, will enhance permafrost degradation if the active layer and the top of the permafrost layer are already preconditioned, i.e. have reduced latent heat content. This preconditioning can already be effectuated by a singular warm year, leading to exceptionally strong melting of the ground ice. On sloping terrain this ice-loss can be considered as irreversible, as large parts of the melted water will drain during the process, and an equivalent build-up of ice in cold years does not happen on similar time-scales as the melting. We propose a simple geophysical approach based on electrical resistivity tomography surveys that can assess the state of preconditioning in the absence of boreholes. In addition, we will show that resistivity data from a total of 124 permafrost sites in the Andes, Europe, and Antarctic adhere to a distinct power law behaviour between unfrozen and frozen states, which confirms the consistent electrical behaviour of permafrost and active layer materials over a wide range of landforms and material composition.

Were the 2022 Summer Heatwaves a Strong Cause of Europe’s Excess Deaths?

During the 2022 summer, Europe experienced heatwaves with record temperatures, and a study has argued that they caused about 62,000 deaths between 30 May and 4 September. The total number of excess deaths during the same period was about 137,000, indicating that the heatwaves were a substantial contributor. Not ruling out that explanation entirely, this paper argues that it was unlikely a strong cause. First, if the heatwaves were a strong cause of numerous deaths, one would assume that the older and deprived were relatively likely to die. However, during the 2022 summer heatwaves in England, which were claimed to have caused about 2900 deaths, the oldest age cohort did not have a higher excess death rate than the middle age cohort, and the excess death rate actually decreased with deprivation status. Moreover, Iceland had among Europe’s highest excess death rates during the summer, which cannot be attributed to heatwaves. During June, July, and August 2022, comparable southern hemisphere countries furthermore had high excess death rates, which cannot be attributed to heatwaves either, as it was during their winter. Also, Europe’s excess death rate was higher during the 2022–2023 winter than during the 2022 summer, and intuitively not attributed to heatwaves, but neither to cold weather, as that winter was abnormally mild. Finally, the paper discusses the puzzling issue that about 56% more women than men, relative to the population, presumably died from the heatwaves.

102 Circadian patterns of behavior, respiration, rectal temperature, saliva melatonin, cytokine concentrations, and milk immune cells are altered by cooling heat-stressed lactating sows

Abstract Lactating sows are particularly vulnerable to heat stress (HS) due to the increased metabolism from milk production. A greater understanding of HS response could assist in mitigating its detrimental effects on animal production. Two core circadian clock genes were pinpointed in a recent genome study as potential mediators of HS response, indicating the possible alteration of circadian clocks by HS exposure. This study aimed to assess how cooling of lactating sows under natural heat stress conditions in the summer influenced circadian patterns of respiration rate (RR), rectal temperature (RT), behaviors, salivary concentration of cortisol and melatonin, milk cell populations and relative abundance of multiple cytokines in saliva. Lactating sows of mixed parities were divided into two treatment groups: treated with electronic cooling pad (C; n=9) and heat-stressed control (H; n=9). Experiments were conducted during two 48 h periods of increased environmental temperatures from summer heatwaves. During the initial 48 h period, rectal temperature (RT) was monitored every 60 min, rectal temperature (RT) every 30 min, and behaviors of eating, standing, sitting, laying, sleeping, drinking, and nursing every 5 min. Morning milk samples were collected following the completion of the first phase and utilized to categorize and count somatic cells. The second trial was approximately 1 wk later, and during this period saliva samples were collected every 4 h over the 48-h period. Results were analyzed for significant effect of treatments and interaction using periodic regression while circadian patterns were further detected by incorporating a Fourier series model utilizing sine-cosine variables that denote a fit and/or shift in circadian pattern. The analysis revealed that cooling decreased RT and RR while also modifying circadian patterns (P < 0.05). Cooling had no impact on the percentage of time spent in any activity over the 48-h period (P > 0.05). Nevertheless, the daily patterns of eating, standing, and sitting were different between the treatments (P < 0.05). A shift in eating time to later in the day in H sows relative to C sows related to a second rise in RT during the dark phase of the light-dark cycle (P < 0.05). Saliva melatonin concentrations were increased in C sows and circadian pattern altered relative to H (P < 0.05), but there was no effect on salivary cortisol concentrations (P > 0.05). Cooling reduced milk lymphocytes (P < 0.05) and influenced diurnal pattern of saliva cytokines including interleukins (IL) IL-1 alpha, IL-1 beta, IL-10, and IL-15 and transforming growth factor-beta 1. In conclusion, the cooling of heat-stressed sows altered the circadian patterns of physiology, behavior and melatonin, suggesting the need for additional research to investigate whether circadian disruption contributes to reduced production efficiency observed in HS animals.

A satellite view of the exceptionally warm summer of 2022 over Europe

Abstract. Summer heatwaves are becoming increasingly dangerous over Europe, and their close monitoring is essential for human activities. Typically, they are monitored using the 2 m temperature from meteorological weather stations or reanalysis datasets. In this study, the 2022 extremely warm summer over Europe is analysed using satellite land surface temperature (LST), specifically the LSA SAF (Land Surface Analysis Satellite Application Facility) all-sky LST product (available from 2004 onwards). Since climate applications of LST are still poorly explored, heatwave diagnostics derived from satellite observations are compared with those derived using ERA5/ERA5-Land reanalysis data. Results highlight the exceptionality of 2022 in different metrics such as the mean LST anomaly, area under extreme heat conditions, number of hot days and heatwave magnitude index. In all metrics, 2022 ranked first when compared with the remaining years. Compared to 2018 (next in all rankings), 2022 exceeded its LST anomaly by 0.7 °C and each pixel had on average 7 more hot days. Satellite LST complements reanalysis diagnostics, as higher LST anomalies occur over areas under severe drought, indicating a higher control and amplification of the heatwave by surface processes and vegetation stress. These cross-cutting diagnostics increase the confidence across satellite data records and reanalyses, fostering their usage in climate applications.

Traces of Local Adaptive Acclimatization Response in the Tracheid Anatomical Traits between Dry and Wet Mesic Norway Spruce (Picea abies) Forests in Moravia, Czech Republic?

Norway spruce (Picea abies) forests in temperate zones are already reacting to short-term extreme summer heatwaves, threatening the vitality of trees and forest productivity, and can even lead to local and regional dieback events. Examining quantitative wood anatomy can provide helpful information in terms of understanding the physiology mechanisms and related responses of conifer trees to local environmental interactions in relation to tracheid adaptive capacity. This study analysed the tracheid functional anatomical traits (FATs) plasticity of six young Norway spruce trees growing in two mesic research plots with high annual precipitation (~43%) and air temperature differences during 2010–2017. The research plots are located in the sub-mountainous (Rájec Němčice) and mountainous (Bílý Kříž) belts of the Moravia region, Czech Republic. Vapour pressure deficit and cell wall reinforcement index (CWRI) were shown to be the most representative environmental parameters as proxies of dry conditions. Tracheid FATs indicated latewood phenological plasticity sensitivity, with more pronounced variability in the warmer and drier plots. Latewood tracheids of Norway spruce trees grown in the RAJ formed significantly thicker cell walls than BK during the studied period. The observed differences between the two research plots indicate additional support for tracheid cells’ hydraulic safety against cavitation and potential traces of adaptive acclimatization response.

Intensified Impact of Spring Tibetan Plateau Snow Cover on Summer Compound Heat Waves in Western Europe after 1998

Abstract This study revealed a significant interdecadal change in the impact of spring western Tibetan Plateau (TP) snow cover (TPSC) on subsequent summer compound heat waves (CHWs) in western Europe (WE) after 1998. This interdecadal change is attributed to a change in a western Europe high–western TP low (WEH–TPL) atmospheric circulation pattern. This pattern arises due to both the inherent variability of TPSC and the phase transition of the Atlantic multidecadal oscillation (AMO) after 1998. The increased magnitude and persistence of western TPSC from spring to summer after 1998 enhanced the snow–atmosphere coupling effect, intensifying ascent and decent motion over the TP and WE, respectively, and strengthening the WEH–TPL pattern. In addition, the post-1998 positive AMO phase favors continuous and stable downstream Rossby wave propagation, enhancing the WEH–TPL pattern and the TPSC–CHWs relationship. Further analyses reveal that the interdecadal changes in the TPSC and the AMO around 1998 contribute to the presence of “double jets” over the North Atlantic–central Eurasian sectors. The TPSC–related anomalous atmospheric circulation and AMO phase shift contribute to the southern and northern branches of the intensified westerly jet, respectively. These conditions create a favorable environment for the formation and persistence of summer CHWs in WE. Numerical modeling experiments with a linear baroclinic model confirm these findings. Our findings suggest that in the context of a changing climate, TPSC plays a pivotal role in the genesis of summer CHWs in WE and may serve as a valuable predictor for CHWs. Significance Statement This study discovered that starting from 1998 there was a significant change in how spring snow cover on the western Tibetan Plateau affects summer compound heat waves in western Europe. After 1998, the snow cover on the western Tibetan Plateau increased in size and lasted longer from spring to summer, intensifying the interaction between the snow and the atmosphere. This led to more rising and sinking air over the Tibetan Plateau and western Europe, respectively. Also, after 1998 a positive phase of the Atlantic multidecadal oscillation (AMO) was favorable for the circulation connection between western Europe and the Tibetan Plateau. Further analysis showed that these changes in snow cover and the AMO after 1998 caused “double jets” in the North Atlantic and central Eurasia that created better conditions for summer heat waves in western Europe. Numerical models are used to confirm these findings. Our research indicates that, in a changing climate, the snow cover on the western Tibetan Plateau plays a crucial role in the development of summer heat waves in western Europe and can be a useful predictor for these heat waves.

Contrasting heat tolerance of evergreen and deciduous urban woody species during heat waves

Abstract The increasing frequency and intensity of heat waves caused significant damages to urban woody species, and the different leaf structures between evergreen and deciduous species may be closely related to leaf heat tolerance. However, whether the different leaf structural traits of evergreen and deciduous plants contribute to their different responses under heat waves is still unclear. During the record‐breaking and long‐lasting 2022 summer heat waves in China, we investigated the relationships between leaf thermal indices and leaf structural traits of 36 urban woody species in four cities along the Yangtze River. We found that all the four thermal indices were significantly but weakly related with leaf damage status. The critical temperature that causes the initial 15% damage to photosystem II (Tcrit) may serve as a sensitive measure of heat tolerance. Evergreen species suffered less leaf damage during the heat waves and exhibited higher leaf heat tolerance, thicker leaves than deciduous species. Tcrit was significantly correlated with leaf mass per area, leaf thickness and thickness of spongy tissue. Synthesis. Urban woody species with higher Tcrit, leaf mass per area and leaf thickness tend to be more tolerant to heat stress. This study provides insights for predicting leaf heat tolerance of urban woody plants in subtropical China and their physiological and ecological responses to severe heat waves. Read the free Plain Language Summary for this article on the Journal blog.

Význam buku lesního ve střední Evropě v období klimatické změny: přehled současných poznatků

In the period of ongoing global climate change, ecosystems, including Central European forests, face significant challenges such as summer droughts and heat waves, which increase the climate risks also for the European beech (Fagus sylvatica L.), an important and dominant broadleaved tree species in this region. This article provides a comprehensive review of current knowledge on the adaptation strategies of European beech in response to changing climatic conditions, highlighting its ecological demands, development of taxonomy, ecological and economic importance and exploring its resilience, growth characteristics, and challenges such as water regime, pests, diseases, and the impact of climate change. A key finding is that despite the various stressors affecting European beech, adaptive management and the use of mixed forest stands can significantly contribute to its conservation and sustainable use. The importance of integrating the genetic diversity and adaptive capacity of European beech into forestry practices is emphasised. The review of 203 studies highlights the need for further research focused on understanding the interactions between European beech and a changing climate in order to develop more effective strategies for its conservation and sustainable management in the future.

Summer heatwaves in China during 1961–2021: The impact of humidity

In additon to temperature, heatwaves are also closely related to humidity. In this study, daily wet-bulb temperature was used to define heatwaves (WBHWs) with a unified threshold for more than 2000 meteorological stations throughout China. The climatic averages of summer heatwaves and changes from 1961 to 2021 were investigated. WBHWs primarily occur in three key subregions, namely North China, South China, and Yangtze River valley (YRV). Humidity makes heatwaves in South China more severe, with an average of 25 days per summer. Over the past decades, the frequency and intensity of WBHWs in China considerably increased accompanied by decreasing relative humidity (RH) and increasing temperature. South China experiences the strongest increase in WBHWs, with change rate fivefold higher than the national average. The occurrence of WBHWs in YRV is dominated by temperature, whereas in North and South China it is controlled by RH. The long-term increases in WBHWs for China and its three key subregions are primarily caused by temperature changes, but RH affects WBHWs at interdecadal time scales and generally exerts a negative contribution. The average contribution rates of temperature and RH to the increase in WBHWs in China for the period 1991–2021 are 2.3 days and − 0.6 days. Changes in WBHWs in North China are almost completely controlled by temperature, since the opposite phases of specific humidity and temperature result in a negligible effect of RH. Temperature and RH in other two subregions have substantial positive and negative effects, respectively. The negative effect of RH in South China is mainly attributed to the indirect effect of temperature, while that in YRV, particularly in the lower reaches, is a combination of specific humidity and temperature.

Summer heatwaves trends and hotspots in the Barcelona Metropolitan Region (1914–2020)

Daily maximum, TX, and minimum, TN, temperatures recorded at Fabra Observatory, for the period 1914–2020 (from June to September), have permitted to identify the daytime and night time heatwaves, HWs, at the Barcelona Metropolitan Region, BMR, along 107 years. Four heatwaves indices have been computed both for maximum and minimum temperatures: the number of events per season, HWN; their maximum duration, HWD; their frequency of occurrence, HWF; and the amplitude of the hottest day event, HWA. Trends in these indices have been obtained and their statistical significance quantified by means of the Mann-Kendall test. For the whole period (1914–2020), positive significant trends have been detected for the four indices, with a marked positive trend since year 2000 for TX, and since 1985 for TN. Nevertheless, when 31-year moving windows have been analysed, both positive and negative significant trends are obtained, being remarkable the change in trend signs around 1960s. The convenience of using the four HW indices is evaluated applying a Principal Component Analysis, PCA, obtaining two principal components. Additionally, the spatial distributions of the MODIS land surface temperatures, LST, corresponding to some extreme heatwaves, permits the detection of two hotspots in the BMR, one for TX and the other for TN. It is also worth mentioning that correlations between the Western Mediterranean Oscillation index, WeMOi, and HW episodes are detected, being notable that, at the beginning of these episodes, WEMOi values are usually lower. These correlations could improve the HWs forecasting.

The subseasonal predictability of the western North Pacific subtropical high and the 2020 record-breaking event

The western North Pacific subtropical high (WNPSH), a prominent feature in the North Pacific during the boreal summer, exerts significant socioeconomic consequences by influencing hydrological extremes such as tropical cyclones, the Meiyu front, and summer heat waves over East Asia. Accurately forecasting the characteristics of the WNPSH over extended timescales is crucial, but subseasonal prediction in this specific context is still in its early stages due to the complex dynamics involved. In this study, we investigate the optimal predictable pattern of the WNPSH using linear stochastic dynamics. Our findings reveal that convection over the Philippine/South China Sea and Japan serves as key precursors, where a dipole vorticity pattern leads to maximum growth of the WNPSH on subseasonal timescales, providing a potential source of predictability. Additionally, we examine the role of optimal predictable patterns in the record-breaking 2020 WNPSH event, and we find that the cumulative effect of stochastic forcing helps explain the sustained features of this extreme case.

Summer heatwaves on the Baltic Sea seabed contribute to oxygen deficiency in shallow areas

Since the early 1980ies, the shallow and brackish Baltic Sea, located in northern Europe, has warmed fastest of all the world’s coastal seas. Hence, the total heat exposure during marine heatwaves increased in frequency and duration, which may have a major impact on the marine ecosystem. We found that marine heatwaves, using two different, commonly used definitions, occurred everywhere on the sea surface since the early 1990s. Periods with sea surface temperatures larger than 20 °C lasting longer than 10 days were particularly numerous in the shallow coastal zone of the southern and eastern Baltic Sea. Furthermore, summer marine heatwaves that reached the seabed mainly occurred in water depths of less than 20 m, where they led to a decrease in oxygen concentration. Since the early 1990s, a positive trend in the expansion of marine heatwaves has been observed on the seabed. The increasing number of marine heatwaves increases the risk of hypoxia events in the coastal zone.

18-years of high-Alpine rock wall monitoring using terrestrial laser scanning at the Tour Ronde east face, Mont-Blanc massif

Since the end of the 20th century, each decade has been warmer than the previous one in the European Alps. As a consequence, Alpine rock walls are generally facing high rockfall activity, likely due to permafrost degradation. We use a unique terrestrial laser scanning derived rockfall catalog over 18 years (2005–2022) compared with photographs (1859–2022) to quantify the evolution of the east face of Tour Ronde (3440–3792 m a.s.l.) in the Mont-Blanc massif (western European Alps) that is permafrost-affected. Overall, 210 rockfalls were identified, from 1 to 15 500 m3. Forty-five events were >100 m3 while cumulated volume of events <10 m3 represents <1% of the fallen rocks. The rockfall magnitude-frequency distribution of the overall inventory follows a power law, with a mean exponent b of 0.44 ± 0.03, characterizing a high contribution of large rockfalls. The depth of failure ranges from a few centimeters to more than 20 m while 95% of the rockfalls depth is <5 m, highlighting the role of the active layer. The mean rock wall erosion rate is 18.3 ± 0.2 mm yr−1 for the 2005–2022 period and ranks in the top range of reported values in the Alps. It has greatly increased between the periods 2006–2014 and 2016–2022, probably in relation to a series of summer heat waves. The exceptional erosion rate of 2015 is driven by one large rockfall in August. Since 2006, an ice apron that covered 16 100 m2 has now almost vanished, and the surface of the glacier du Géant at the rock wall foot has lowered by several tens of meters. The retreat of these two ice masses contributed to the rock wall instability as more than 35% of the rockfall volume detached from the deglaciated surfaces.

Revealing trends in extreme heatwave intensity: applying the UNSEEN approach to Nordic countries

The increase in heatwave intensity, causing heat stress and crop failures in many regions is a concerning impact of global climate change. In northern Europe, significant interannual variability previously prevented robust assessments of trends in heat extremes. However, with a large-ensemble seasonal hindcasts and archived forecasts dataset covering 1981–2022 multiple realisations of weather patterns can be pooled and assessed. What are recent trends of extreme temperatures? Has the risk for a 100-year heatwave event increased in Northern Europe? We apply the UNSEEN (UNprecedented Simulated Extremes using ENsembles) approach to assess the credibility of the model ensemble and use non-stationary extreme value analysis to quantify recent trends in extreme 3-day heatwaves in late spring and early summer (May to July). We find significant non-stationarity and positive trends in annual maximum heatwave intensity. We also show that heatwave volatility, i.e. the risk of clearly outstanding heatwaves, is highest in central Scandinavia.

Uneven evolution of regional European summer heatwaves under climate change

Heatwaves (HWs) are extreme events magnified under climate change with critical implications for the human and environmental systems they impact. These phenomena are generally investigated as a large-scale effect over extensive regions. However, their regional-to-local characteristics and trends are responsible for the specific effects on local communities. This study presents a comprehensive analysis of the characteristics and evolution of regional HWs covering the 1950 to 2021 period across different European climates, central Europe (CE), France (FR), and the Iberian Peninsula (IP), including an analysis of the local and remote relationship between summer heat periods and winter-spring precipitation conditions. Our results confirm the general increase in frequency, intensity, duration, and spatial extent of the HW phenomena over the three domains but point out their uneven evolution under climate change. While a larger frequency increase in the number of heat periods affects IP and FR, it is over CE, where the largest frequency change is observed in the most recent decades. Over north-western FR and CE the most intense HW events have recently registered, further over CE HWs’ long-lasting durations between five to six days have tripled from the sixties to recent decades. It is indeed over the latter that a substantial increase in human exposure to HW phenomena is observed. Probably, the unalike progressions are related to the proven differential rate of warming between the mean and hottest days at northern and southern European domains and the influence of soil conditions over IP on the development of summer heat periods over FR and CE.

Heatwaves in summer 2022 forces substantial mass loss for Urumqi Glacier No. 1, China

Abstract Extreme heat events in the summer of 2022 were observed in Eurasia, North America and China. Glaciers are a unique indicator of climate change, and the European Alps experienced substantial glacier mass loss as a result of the conditions in 2022, which prompted a wide range of community concerns. However, relevant findings for glaciers in China have not been currently reported. Here, we document the response of Urumqi Glacier No. 1 in the eastern Tien Shan to the extreme heat observed in 2022 based on in situ measurements that span more than 60 years. In 2022, Urumqi Glacier No. 1 exhibited the second largest annual mass loss on record, and the summer mass balance was the most negative on record. The hottest summer on record and relatively lower solid precipitation ratio contributed to the exceptional mass losses at Urumqi Glacier No. 1 in 2022, demonstrating the significant influence of heatwaves on extreme glacier melt in China.

Inferring the impacts of climate extreme in the Kabul River Basin

The increasing temperature and variability in precipitation, in terms of both frequency and intensity, are affecting different sectors in the Himalayan region. This study aims to quantify the future scenario and related extremes in the Kabul River Basin (KRB) of the western Himalaya using high-resolution climate datasets. We selected four representative General Circulation Model (GCM) runs from Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios, based on future projections, climatic extremes and their abilities to represent the historical climate cycle (1981–2010) of KRB. The seasonal analysis of precipitation shows decreasing pattern during the winter and pre-monsoon seasons and annual mean temperature will increase consistently by 3 to 5 °C in RCP4.5 and 8.5 scenarios. Ten indices were selected to study climatic extremes pertaining to the health, agriculture and water resources sectors. The extremes, like consecutive summer days, warm days and heatwaves, will increase, whereas the frost days, cold nights, cold waves and extreme precipitation days will decrease towards the end of this century. Besides, the extremes are not homogenous in time and space. Based on the results of this study, there is a need for prompt climate actions in order to increase the adaptive capacity against these extreme changes and to build resilient livelihoods in the KRB.

The Heatwave of Summer 2022 in the North-Western Mediterranean Sea: Some Species Were Winners

The warming trend of the Mediterranean Sea is a long-term process. It has resulted in a northwards and westwards range expansion and abundance increase of thermophilic species, both native and non-indigenous, and in a shrinking of the range of cold-affinity species. Marine heatwaves (MHWs) are relatively short-term extreme episodes that are responsible for spectacular mortality events in some species and have been extensively reported in the literature. In contrast, the species that benefit from MHWs (the ‘winners’) have been much less studied. A record-breaking MHW occurred in 2022 in the north-western Mediterranean Sea. We focus on three ‘winner’ species, the thermophilic green macroalgae Penicillus capitatus and Microdictyon umbilicatum and the endemic seagrass Posidonia oceanica. Penicillus capitatus, which is mainly present in the area as an inconspicuous turf of entangled filaments (espera stage), produced the erect paintbrush-like stage where sexual reproduction takes place. Microdictyon umbilicatum, usually uncommon, bloomed to the point of clogging fishing nets. Finally, a mass flowering of P. oceanica occurred in late August–September, followed the following year (April–May 2023) by the extensive production and dissemination of fruits and seeds. Both processes, the long-term warming trend and one-off heatwaves, both ‘losers’ and ‘winners’, shape the change in structure and functioning of Mediterranean ecosystems.