Virgilio A. Bento

Due to ongoing global warming, the frequency and intensity of extreme weather events have increased substantially. Compared to individual extremes, compound drought and high temperature (CDHT) events represent a major climate risk in China. However, their spatiotemporal characteristics remain insufficiently understood, particularly at fine temporal scales. To address this gap, this study systematically investigated CDHT events across China from 1982 to 2023. Methodologically, CDHT events were identified at the raster level by combining an improved daily Standardized Precipitation Evapotranspiration Index (SPEI) with daily maximum temperature using a quantile relative dynamic threshold. The results show strong spatial heterogeneity: the longest event durations are primarily observed in Xizang, while higher event severity is concentrated in regions south of 30° N. Trend analysis reveals a widespread increase in the duration, frequency, and severity of CDHT events across most of China, with the most pronounced intensification detected in Xinjiang, Inner Mongolia, and Yunnan. Overall, these findings highlight a clear climate-driven intensification of CDHT events, offering new insights into their spatiotemporal dynamics. The results offer a robust scientific basis for improving risk assessment and developing targeted adaptation strategies to mitigate the impacts of compound climate extremes in China.

The Mediterranean region is widely recognized as a climate-change hotspot, where rising temperatures and declining precipitation are expected to intensify hydroclimatic stress. Most Mediterranean countries already experience increasing drought frequency and persistent soil moisture deficits leading to changes in terrestrial water storage. However, projected changes in the seasonal structure of soil moisture and its joint behaviour with temperature and precipitation remain insufficiently quantified.Here, we assess future projections of soil moisture dynamics and compound warm–dry conditions across the Mediterranean using a multi-model ensemble of EURO-CORDEX regional climate simulations. We analyse daily total soil moisture, precipitation, 2-m temperature, and potential evapotranspiration for a historical baseline period (1971–2000), and three future periods (2011–2040, 2041–2070, 2071–2100) under three emission scenarios (RCP2.6, 4.5 and 8.5). Seasonal amplitude and phase changes in soil moisture are examined, and joint probability density functions are used to quantify compound warm–dry conditions and their drivers.The projections show a clear reduction of soil moisture throughout the entire annual cycle, in response to a significant decrease in precipitation and an increase in temperature, leading to a substantial rise in potential evapotranspiration. The overall total soil moisture decreases ranges from -5% for the RCP2.6 to -20% (-10%) for the RCP8.5 (RCP4.5), with relation to the present climate. Projections reveal that for the RCP4.5 (RCP8.5) for the mid-century soil moisture deficits up to 5x (6x) are projected to occur, and for the end-of-century even 7x for the RCP8.5. Our results show a robust amplification of soil moisture seasonal amplitude across all Mediterranean sub-regions, increasing with higher greenhouse gas emissions and toward the end of the century. The largest increases are projected over the eastern Mediterranean, reflecting enhanced seasonal contrasts driven by intensified summer drying. Despite these amplitude changes, the phase of the soil moisture annual cycle remains stable across scenarios, indicating that climate change primarily intensifies existing seasonal dynamics rather than shifting their timing. Joint probability analyses show a substantial increase in the likelihood of compound warm–dry conditions, particularly under RCP4.5 and, more pronounced under RCP8.5, during mid- and late-century periods.Overall, our findings highlight that future Mediterranean hydroclimatic risk is driven not only by mean drying but also by a pronounced intensification of soil moisture variability and compound extremes. These projections have important implications for ecosystem, water resources, and climate adaptation strategies. This work is supported by FCT, I.P./MCTES through national funds (PIDDAC): LA/P/0068/2020 - https://doi.org/10.54499/LA/P/0068/2020, UID/50019/2025, https://doi.org /10.54499/UID/PRR/50019/2025, UID/PRR2/50019/2025. The authors would like also to acknowledge the project “Elaboração do Plano Municipal de Ação Climática de Barcelos (PMACB). This work was performed under the scope of project https://doi.org/10.54499/2022.09185.PTDC (DHEFEUS). DCAL acknowledge FCT I.P./MCTES (Fundação para a Ciência e a Tecnologia) for the FCT https://doi.org/10.54499/2022.03183.CEECIND/CP1715/CT0004.

European wildfire response systems are increasingly challenged by the simultaneous demand for aerial and ground suppression assets. If major fire-prone regions burn asynchronously, Europe could benefit from risk-diversified deployment of shared suppression fleets and more efficient cross-border mutual-aid strategies. We test the hypothesis that fire activity in (1) the Iberian Peninsula (Portugal and Spain) and (2) Central–Eastern Mediterranean (Italy and Greece) exhibits identifiable and temporally stable dependence patterns modulated by large-scale climate variability.Annual burned-area time series covering 1980–2023 are compiled from the European Forest Fire Information System (EFFIS). These are complemented by satellite-derived indicators of fire activity from MODIS, namely Fire Radiative Power (FRP), enabling joint assessment of burned area extent and fire intensity. Climate-fires’ dependence is quantified through correlations of annual and seasonal anomalies and joint-extreme metrics focused on tail co-exceedance probability. The relationship between fire activity (burned area, FRP, FRE) and large-scale climate variability is assessed following established teleconnection-based frameworks, combining seasonal aggregation, lagged cross-correlation analysis, and composite analysis of extreme fire years. Teleconnection indices considered include the North Atlantic Oscillation (NAO), East Atlantic pattern (EA), Mediterranean Oscillation Index (MOI), Arctic Oscillation (AO), and ENSO. Analyses explicitly account for the non-stationary and scale-dependent nature of teleconnection–fire relationships, and are conditioned on regional temperature and precipitation anomalies to isolate circulation-driven effects.The analysis aims to identify: (i) the frequency and persistence of synchrony versus compensatory (negative) dependence in burned area and fire activity between the two macro-regions, (ii) the teleconnections most strongly associated with synchronous extreme fire seasons, and (iii) multi-decadal periods offering potential for suppression-fleet diversification. Owing to its direct control on Mediterranean-scale pressure gradients and precipitation contrasts, MOI provides the primary explanatory signal for synchronous versus compensatory fire activity between the two macro-regions.Results are interpreted within an operational risk-pooling framework, where weak or negative dependence supports climate-informed scheduling of shared European suppression fleets and enhanced cross-border mutual aid, while strong positive dependence indicates heightened likelihood of concurrent continental-scale resource strain. This work is partially supported by FCT, I.P./MCTES through national funds (PIDDAC): LA/P/0068/2020 – https://doi.org/10.54499/LA/P/0068/2020, UID/50019/2025 – https://doi.org/10.54499/UID/PRR/50019/2025, UID/PRR2/50019/2025 and Dhefeus (https://doi.org/10.54499/2022.09185.PTDC). AR, JMCP and JMNS also thank the FCT by supporting UIDB/00239/2020 (https://doi.org/10.54499/UIDB/00239/2020), UIDP/00239/2020 (https://doi.org/10.54499/UIDP/00239/2020), and through project references UIDB/00239/2020 (https://doi.org/10.54499/UIDB/00239/2020) and UIDP/00239/2020 (https://doi.org/10.54499/UIDP/00239/2020) and European Space Agency Climate Change Initiative (ESA-CCI9 Tipping Elements SIRENE project (Contract No. 4000146954/24/I-LR).

Climate change is intensifying the frequency, severity, and interactions of extreme heat, drought, wildfires, and air pollution, increasing risks to both ecosystems and human populations worldwide. These risks can emerge from the accumulation of multiple hazards over time (multi-hazard risk), but also from their simultaneous co-occurrence (compound events). Here, we present a global, spatially explicit assessment of human risk from wildfires and air quality associated with hot and dry extremes, explicitly integrating multi-hazard and compound risk representations, following a hazard, exposure, and vulnerability perspective.Using global datasets at 0.75° spatial resolution for the period 2003–2022, hazards are quantified based on the number of hot days per month (derived from exceedances of daily maximum temperature above the 90th percentile of a 1991–2020 climatology), drought occurrence (as depicted by the 6-month Standardized Precipitation–Evapotranspiration Index, SPEI), wildfire activity (characterized using MODIS Fire Radiative Power, FRP), and the number of days with PM2.5concentrations exceeding World Health Organization air quality thresholds. Human exposure is represented exclusively by gridded population density, while vulnerability is characterized using indicators capturing human sensitivity and adaptive capacity, e.g., the Human Development Index (HDI) and Water Stress Index (WSI).Human risk is quantified by combining hazard intensity, population exposure, and vulnerability, following both a multi-hazard and a compound formulation. In a multi-hazard formulation, hazards are aggregated without requiring temporal co-occurrence, capturing the cumulative burden of climate extremes. In parallel, compound risk is assessed by explicitly accounting for the co-occurrence of hazards within the same temporal windows, enabling a direct comparison between cumulative and compound representations of risk. In addition, we quantify the global population affected by different risk classes. Our estimates indicate that approximately half of the world’s population is currently exposed to high to very high risk, while a substantially smaller fraction resides in low or extremely low risk conditions. High and very-high risk classes together account for several billion people, underscoring the widespread nature of climate-related human risk. When aggregated at the country level, risk levels exhibit a clear socioeconomic gradient, with higher average risk values concentrated in lower-income countries, low life expectancy at birth, and high infant mortality rate.The results illustrate how a compound events perspective can alter the spatial distribution and relative intensity of human risk compared to a multi-hazard one, highlighting regions where hazard interactions may further amplify societal impacts. This work provides a generalized framework for global human risk assessment, offering new insights into how different representations of climate extremes shape risk patterns and supporting the development of more effective adaptation and risk reduction strategies.This work is supported by FCT, I.P./MCTES through national funds (PIDDAC): LA/P/0068/2020 - https://doi.org/10.54499/LA/P/0068/2020, UID/50019/2025, https://doi.org /10.54499/UID/PRR/50019/2025, UID/PRR2/50019/2025. This work was performed under the scope of project https://doi.org/10.54499/2022.09185.PTDC (DHEFEUS) and the Horizon Europe research and innovation programmes under grant agreement number 101081661 (WorldTrans).

Climate change imposes a substantial strain on global societies, compelling pragmatic, and timely adaptation measures to secure future prosperity while mitigating the impact of increasingly frequent and intense extreme events, such as wildfires. Compound drought and heatwaves further amplify the wildfire challenge, potentially impacting human health through a decrease in air quality. This underscores the need for concentrated attention and action. These events, with repercussions spanning continents and biomes, pose challenges for authorities striving to prepare effective responses. Our focus is on mainland Portugal, situated in the Mediterranean climate change hotspot, where we analyze the influence of diverse adaptation strategies on wildfire risk.Using a weighted ensemble of regional climate models from the EURO-CORDEX initiative, we project the Fire Weather Index (FWI) and Fire Radiative Power (FRP) across various Representative Concentration Pathways (RCPs). Our findings indicate a potential three-fold increase in the occurrence of highly energetic fires, with energy releases surpassing 1000 MW, contingent upon the chosen RCP. Even under robust mitigation scenarios, the probability of megafires — those with energy releases exceeding 1000 MW — experiences a notable upsurge of approximately 1.5-fold. This emphasizes the imperative for proactive adaptation measures irrespective of ongoing mitigation endeavors.We introduce three distinct mitigation strategies designed to simulate fire prevention policies targeting the most intense fires in diverse climate change scenarios. The most promising outcome entails a reduction in wildfires exceeding 1000 MW by 20 to 60%, an achievement realizable through preventing 95% of hotspots in regions characterized by extreme fire danger. This suggests that an immediate imposition of overly restrictive and costly policies throughout the summer months may not be imperative. Instead, implementing targeted strategies in critical fire danger areas could substantially mitigate the occurrence of destructive megafires.This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). This work was performed under the scope of project https://doi.org/10.54499/2022.09185.PTDC (DHEFEUS) and supported by national funds through FCT. AR acknowledge FCT I.P./MCTES for the FCT https://doi.org/10.54499/2022.01167.CEECIND/CP1722/CT0006. The authors would like to acknowledge the project “CEASEFIRE: Envio e disseminação de alertas automatizados de gestão de perigo meteorológico de incêndio”, financed by The Navigator Company.

Understanding the risks associated with climate change and variability, particularly related to the frequency and intensity of heatwaves, droughts, wildfires, and pollution, is crucial for safeguarding public health and safety. As global temperatures rise, hot and dry conditions become more prevalent, exacerbating the likelihood of devastating wildfires that not only destroy ecosystems but also release harmful pollutants into the air. Pollutants from these events, desert plumes, industry, and other sources, including particulate matter, pose significant respiratory and cardiovascular risks to the population, particularly vulnerable groups such as children, the elderly, and those with preexisting health conditions. Comprehensive awareness and proactive measures are essential to mitigate these risks, ensuring that communities are better prepared to adapt and respond to the escalating challenges posed by our changing climate.In this work, we adopt the IPCC's definition of risk, which encompasses the potential for adverse consequences due to the interplay of hazards, exposure, and vulnerability. We analyse climate-related hazards including heatwaves, droughts, fires measured by fire radiative power, and pollution quantified as PM2.5 levels. These hazards are assessed in conjunction with population characteristics that determine exposure, such as population density. Furthermore, we evaluate vulnerability through socio-economic variables like the Human Development Index (HDI) and GDP per capita, which provide insights into the sensitivity and adaptive capacity of the different communities. By integrating these elements, our study aims to comprehensively understand and quantify the risks posed by climate to human and ecological systems at the global level.Results indicate that populations in Western and Eastern Africa, as well as Southeastern Asia, are most at risk from the combined impacts of heatwaves, droughts, and fires. The Mediterranean region, particularly the African Mediterranean and Greece are also at risk concerning hot and dry events. However, the Mediterranean regions are not particularly at risk from the combined effects of fire and pollution. These regions are characterized by significant exposure to extreme weather events and varying levels of vulnerability due to socio-economic factors. When considering pollution alone, regions such as Western Africa, the Indian subcontinent, and Eastern and Southeastern Asia face particularly high levels of risk, primarily due to elevated concentrations of PM2.5 pollutants. The intersection of high exposure and vulnerability in these areas underscores the urgent need for targeted interventions and adaptive strategies to mitigate the adverse health and environmental impacts of these climate-related hazards.This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). This work was performed under the scope of project https://doi.org/10.54499/2022.09185.PTDC (DHEFEUS) and supported by national funds through FCT. DL and AR acknowledge FCT I.P./MCTES (Fundação para a Ciência e a Tecnologia) for the FCT https://doi.org/10.54499/2022.03183.CEECIND/CP1715/CT0004 and https://doi.org/10.54499/2022.01167.CEECIND/CP1722/CT0006, respectively.

Recently, there has been increasing attention on the complex interactions among environmental and climatic stressors, including heatwaves, droughts, and poor air quality or fires, which are intensified by climate change. These stressors, classically considered individually, are now understood to be interconnected phenomena with far-reaching global impacts. Moreover, the cumulative effects of these events have often higher impacts than isolated events, with far-reaching consequences for ecosystems, economies, and public health on a global scale. This study provides a detailed examination of compound events involving heatwaves, droughts, fires, and poor air quality worldwide, elucidating their interconnected nature, triggering drivers, and consequences for ecosystems and societies.To conduct this analysis, meteorological data from ERA5 were utilized to identify droughts using the Standardized Precipitation-Evapotranspiration Index (SPEI) and heatwaves, while Fire Radiative Power (FRP) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Terra and Aqua satellites was selected, along with air quality data (specifically particulate matter PM2.5) obtained from the Copernicus Atmosphere Monitoring Service (CAMS) global reanalysis (EAC4). Compound events were identified based on the detection of pollution events, heatwaves, droughts, or FRP occurring in various combinations.The analysis revealed hotspots of compound events concentrated in different regions worldwide. For example, instances of pollution and heatwaves were predominantly observed in India, the Arabian Peninsula, and eastern China, while heatwaves and fires were more common in the Brazilian Cerrado, northern Australia, and South African Savannas. The Mediterranean region is particularly affected by hot and dry events, whereas Greece, Portugal, and Italy are those more affected by the compound of hot, dry, fire and pollution hazards. The impacts of single and simultaneous occurrences of hot, dry, and fire events on particulate matter PM2.5 levels varied significantly by continent, with North America and Asia experiencing notably higher pollution levels during simultaneous events compared to isolated pollution events.The intersection of compound hot and dry events with wildfires presents a significant public health challenge, highlighting the interrelation of climate change, extreme weather events, and air pollution. Addressing these complex relationships requires comprehensive strategies that integrate climate resilience, wildfire management, and air quality regulations to protect human health and well-being in the face of a changing climate.This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). This work was performed under the scope of project https://doi.org/10.54499/2022.09185.PTDC (DHEFEUS) and supported by national funds through FCT. DL and AR acknowledge FCT I.P./MCTES (Fundação para a Ciência e a Tecnologia) for the FCT https://doi.org/10.54499/2022.03183.CEECIND/CP1715/CT0004 and https://doi.org/10.54499/2022.01167.CEECIND/CP1722/CT0006, respectively.

Soil moisture is a key hydrologic state variable driving the exchange of water and heat energy between the land surface and the atmosphere through evaporation and plant transpiration, regulating surface temperature, humidity and potentially affect precipitation though recycling processes. Soil moisture is a fundamental element of the surface water budget, determining the health or stress on land surface ecosystems and managed systems such as agriculture and agroforestry. The surface water budget, and therefore soil moisture, depends on precipitation, irrigation (when present), soil infiltration, surface runoff, baseflow, and evapotranspiration. Furthermore, soil moisture-based indices are used as indicators of agricultural droughts, and soil moisture drought is one of the preconditioning effects for the development of extreme temperatures, influenced by atmospheric dynamics.Climate change poses a major threat to all Mediterranean countries due to the combination of significant reductions in precipitation, increases in temperature, and the higher frequency of climate extremes, especially driving water scarcity and related multi-sectoral impacts. Most Mediterranean countries already endure higher frequencies of droughts and deficits in soil moisture and water storage. In this study, future projections of soil moisture are examined using a multi-model EURO-CORDEX regional climate ensemble, in agreement with three future emission scenarios (RCP2.6, 4.5 and 8.5). The drivers of future soil moisture dynamics are also analysed along with their effects on relative humidity and evaporation rates.As expected, the projections show a clear reduction of soil moisture throughout the entire annual cycle, in response to a significant decrease in precipitation and an increase in temperature, leading to a substantial rise in potential evapotranspiration. The overall total soil moisture decreases ranges from -5% for the RCP2.6 to -20% (-10%) for the RCP8.5 (RCP4.5), w.r.t. the present climate. Projections reveal that for the RCP4.5 (RCP8.5) for the mid-century soil moisture deficits up to 5x (6x) are projected to occur, and for the end-of-century even 7x for the RCP8.5. The annual cycle of soil moisture, both in the present and future climate, is determined by precipitation and potential evapotranspiration, and deficit is both enhanced and covers a wider monthly window in the future, especially for the RCP8.5. This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020(https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020(https://doi.org/10.54499/LA/P/0068/2020). This work was performed under the scope of project https://doi.org/10.54499/2022.09185.PTDC (DHEFEUS) and supported by national funds through FCT. DL and AR acknowledge FCT I.P./MCTES (Fundação para a Ciência e a Tecnologia) for the FCT https://doi.org/10.54499/2022.03183.CEECIND/CP1715/CT0004 and https://doi.org/10.54499/2022.01167.CEECIND/CP1722/CT0006, respectively.

Europe, particularly the Mediterranean region, faces an escalating threat from extreme weather events like heatwaves and droughts. These events are projected to worsen under climate change, impacting agriculture, water resources, and society.This study delves into the individual and combined occurrences of heatwaves and droughts across Southern Europe. We investigate the interplay between soil moisture and atmospheric water vapor using high-resolution ERA5 climate data. We analyze trends in heatwave duration, intensity, and drought frequency. Additionally, we assess changes in soil moisture, average temperature, and precipitation. Furthermore, the study explores linkages between large-scale climate patterns like the North Atlantic Oscillation (NAO) and the occurrence of these extreme events.Our results indicate an upward trend in both drought and heatwave intensity and duration. Soil moisture exhibits a concerning decline, with statistically significant negative trends across extensive regions. We also observe a rise in average temperatures alongside a slight decrease in average precipitation.This research anticipates an increase in the frequency, duration, and intensity of combined heatwave and drought events. This trend is likely driven by climatic phenomena such as synoptic systems and preceding soil moisture conditions. Our findings aim to enhance the representation of these complex interactions within climate models, leading to improved projections of extreme events in the Mediterranean. This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). This work was performed under the scope of project https://doi.org/10.54499/2022.09185.PTDC (DHEFEUS) and supported by national funds through FCT. DL and AR acknowledge FCT I.P./MCTES (Fundação para a Ciência e a Tecnologia) for the FCT https://doi.org/10.54499/2022.03183.CEECIND/CP1715/CT0004 and https://doi.org/10.54499/2022.01167.CEECIND/CP1722/CT0006, respectively.