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Uncertainty in the frequency of compound hot-dry events (fHD) in idealised experiments (Note that an in-depth interpretation of the figure is provided in the Supplementary Material.) Given a present-day bivariate Gaussian distribution of temperature T and precipitation P with a correlation cor(T, P) of -0.5 (first row), 0 (second row), and 0.5 (third row), shading shows the uncertainty in the future fHD associated with uncertainty in the change of mean temperature (left column) and mean precipitation (right column) at given levels of expected changes in mean temperature (shown on the x-axis) and mean precipitation (y-axis). Magenta isolines show the expected fHD resulting from the expected changes in mean temperature and precipitation (they are the same on right and left columns for a given cor(T, P)). The second axes show changes in units of present-day standard deviations. The closed contour shows the kernel density containing 90% of the multimodel mean projected changes in mean temperature and precipitation in units of relative present-day standard deviations over land grid-points (actual changes in ∘C and mm/day are shown in Extended Data Figure 2b and 7b, respectively). The green line indicates changes of equal magnitude in temperature and precipitation, in units of present-day standard deviations. (Note that the difference in magnitude of uncertainty from temperature (left column) and precipitation (right column) results from the fact that the uncertainty in the change of temperature is relatively large compared to the uncertainty in the change of precipitation).
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Compound hot–dry events—co-occurring hot and dry extremes—frequently cause damages to human and natural systems, often exceeding separate impacts from heatwaves and droughts. Strong increases in the occurrence of these events are projected with warming, but associated uncertainties remain large and poorly understood. Here, using climate model large...
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... Droughts are typically slow-onset climate extreme events (Mishra and Singh, 2010), yet they can be disruptive and affect millions of people every year (Below et al., 2007;Enenkel et al., 2020). Heatwaves can intensify and trigger a faster drought evolution (Bevacqua et al., 2022). Compound droughts and heatwaves can strongly impact socio-economic and ecological systems and may even compromise our ability to reach the United Nations (UN) sustainable development goal on climate action while strongly reducing the Earth system's current natural capacity to absorb and store carbon (Yin et al., 2023). ...
Droughts and heatwaves are among the most impactful climate extremes. Their co-occurrence can have adverse consequences on natural and human systems. Early information on their possible occurrence on seasonal timescales is beneficial for many stakeholders. Seasonal climate forecasts have become openly available to the community, but a wider use is currently hindered by limited skill in certain regions and seasons. Here we show that a simple forecast metric from a multi-system ensemble, the signal-to-noise ratio, can help overcome some limitations. Forecasts of mean daily near-surface air temperature and precipitation in boreal summers with a high signal-to-noise ratio tend to coincide with observed larger deviations from the mean than summers with a low signal-to-noise ratio. The signal-to-noise ratio of the ensemble predictions may serve as a complementary measure of forecast reliability that could benefit users of climate predictions.
... (i.e. when both conditions need to be fulfilled at the same time). In fact, as 247 noted by e.g.Bevacqua et al (2022), using more restrictive thresholds (such as the 99th 248 percentile threshold instead of the 90th) drastically reduces the probability of occurrence in 249 the observed period.250 Finally, to define a compound hot and dry (CHD) event we use the empirical approach based 251 on the concurrence of exceedance of the two indicators (Hao et al 20022): namely, a CHD 252 event is defined when both the above conditions (HW and drought events) occur in the same 253 location in the same year. ...
... Ranasinghe et al 2021, Russo et al 2019, Spinoni et al 2020, Tabari and Willems 2023), 550and also corroborating the claims that future CHD events will be mainly constrained by the 551 precipitation signal(Bevacqua et al 2022) which, at regional sale, can be often masked by 552 natural variability especially for low-or medium-emission scenarios (Doblas- ...
After analysing observed summer compound hot and dry (CHD) events over Europe from 1950 to 2022, we employ a large ensemble of high-resolution regional climate model simulations to investigate CHD events under different emission scenarios.
By the end of the century, even under a low-emission scenario, model results show a likely increase in the frequency and extension of CHD events over most (60%) of Europe. In particular, the fraction of land projected to be hit once every two years nearly doubles (at least 15%, likely range 6-21) compared to the historical period (8%, 6.5-10), and at least 5,3% (1-7) of land will be hit every year.
Under a high-emission scenario, 50% of the Iberian Peninsula is projected to be hit at least twice every three years (20.3 times in 30 years, likely range 17.2-24.2), compared to 1 in ten years in the historical period, whereas 50% of the British Islands, France, and the Mediterranean will be hit more than once every two years. Moreover, 10% of European land will be hit nearly once every 7 years (4.2 times, 3.2-5.6) by CHD events whose intensity equalled or even surpassed the maximum recorded during 1950-2022, and 20% of the Iberian Peninsula once every 5 years. The increase in record-breaking or unprecedented CHD events is mostly related to the increase in record-breaking heatwaves, which is likely over most regions even for the low-emission scenario. In contrast, the increase in record-breaking drought events is limited to southern Europe under the medium- and high-emission scenarios.
... Following Bevacqua et al. (2022), we evaluated the effect of sample size on the relative uncertainty quantification and compound climate extreme indeices calculations. Since the MPI-GE model has numerous ensemble members (100), we selected it to explore these issues. ...
Compound climate extremes (here referred to compound dry–hot events and compound pluvial–hot events) result in devastating disasters which threaten water‐food‐energy security. However, in a warming scenario, the risk of occurrence, the quantification of uncertainty, and associated drivers of compound climate extremes—particularly compound pluvial–hot events—have not been fully explored. By leveraging climate model large ensembles, it is revealed that the risk of compound climate extremes is projected to increase 2–3 times over most global land masses in future Representative Concentration Pathway (RCP) 8.5 forcing compared with historical forcing. Increased risks of compound climate extremes are mainly attributed to the changes in temperature and changes in dependence between precipitation and temperature, while the change in precipitation contributing to risk of these two compound climate extremes exhibits approximately spatial complementary. In the warming world, the hot spots of compound dry–hot extremes mainly lie in Europe, South Africa, and the Amazon, while those of compound pluvial–hot extremes mostly lie in the eastern USA, eastern and southern Asia, Australia, and central Africa. These findings help stakeholders and decision makers develop a package of climate change adaptation strategies to manage and mitigate the risk of compound climate extremes.
... In order to obtain warming-based reference periods of 0.7, 1.2, 1.5 and 2.0°C, we calculated the mean warming of each model over all ensemble members as compared to the reference period of 1950-1969. In line with related work 51 , we selected the first 20-year period in which the respective warming level is reached, including the adjustment of 0.25°C of observed warming that occurred until 1950-1969 against a historic reference period of 1850-1900 (on the basis of the observational HadCRUT5 dataset 52 ). Hence, the different SMILEs don't necessarily cover the same years for a given level of global warming, as shown in Table 1. ...
Heat-related mortality has been identified as one of the key climate extremes posing a risk to human health. Current research focuses largely on how heat mortality increases with mean global temperature rise, but it is unclear how much climate change will increase the frequency and severity of extreme summer seasons with high impact on human health. In this probabilistic analysis, we combined empirical heat-mortality relationships for 748 locations from 47 countries with climate model large ensemble data to identify probable past and future highly impactful summer seasons. Across most locations, heat mortality counts of a 1-in-100 year season in the climate of 2000 would be expected once every ten to twenty years in the climate of 2020. These return periods are projected to further shorten under warming levels of 1.5 °C and 2 °C, where heat-mortality extremes of the past climate will eventually become commonplace if no adaptation occurs. Our findings highlight the urgent need for strong mitigation and adaptation to reduce impacts on human lives.
... However, there are also studies indicating that increasing trend is not typical for each place. For example in Poland it was found increasing trend in south-east part but in the same time decreasing trend was noticed in the west [4,6,7,5,8,9,2]. ...
The type of precipitation is one of the factors taken into consideration when deciding on the most optimal drainage system. Drainage systems are used to prevent the landslides caused by water erosion. Rainfall affect the rate of infiltration and the intensity of surface runoff and thus the occurrence, course and effectiveness of erosion processes [1, 2, 3]. Knowledge of local precipitation trends will help to apply precautions and thus minimise the risk of adverse events such as landslides. What is more it can help more effectively manage projects risks and costs. The aim of this study was to analyse more than 30 years of data from daily rainfall measurements from the Podkarpackie Voivodeship and to check whether the occurrence of precipitation is a random event or whether it indicates long-term trends that may affect changes in ground stability. The non-parametric Mann-Kendall test and correlation test were used for the analysis.
... In total, 93-95% of the world population is projected to experience more than double the current number of hot/dry events by the end of the twenty-first century (Ridder et al. 2022). Using climate model large ensembles, Bevacqua et al. (2022) show that mean precipitation trends exclusively modulate the future occurrence of hot/dry compound events over land. The role of precipitation deficits in modulating and/or amplifying extreme climate events has already been demonstrated in several studies (Oglesby and Erikson 1989;Atlas et al. 1993;Fisher et al. 2007aFisher et al. , 2007bHirschi et al. 2011;Mueller and Seneviratne 2012;Whan et al. 2015). ...
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High‐tide flooding (HTF) is usually generated by a variety of different processes acting at different temporal scales across different geographic regions, but little is known about the role of interactions between those. We assess the role of compounding effects arising from cross‐covariances between different sea‐level components in generating HTF events along the US coastline. Our results show that compounding effects contribute to both HTF frequencies and magnitudes. The US Gulf and northwest coasts exhibit particularly high potential for compound HTF. Long‐term sea‐level rise is the main driver of accelerated HTF frequencies along the US coastline. However, even in the absence of sea‐level rise, changes in compounding effects due to increased or decreased cross‐covariances between sea‐level components associated with climate variability and change also modulate compound HTF. Our results highlight the importance of adequately modeling compounding effects between sea‐level components when generating future projections of HTF.
... We used the Taylor diagram (Fig. S10) to evaluate the performance of the selected models and found that the ensemble mean of multiple models outperformed a single one. Although the CMIP6 model improves simulations of climate extremes (Chen et al. 2020a;Zhu et al. 2021), a larger sample and corrected deviations in the data are needed in future research to reduce the uncertainty (Bevacqua et al. 2022). Furthermore, differences in the thresholds may also induce uncertainty since we adopt different percentiles (e.g., 25th, 75th, 10th, and 90th) as thresholds to define compound extreme days. ...
... More advanced and high-resolution socioeconomic data (both spatial and temporal data) could help generate more accurate projections (Zhao et al. 2022). In recent years, the understanding of extreme events has been deepened, the research on compound extreme events has been enriched, and a series of advances have been made (Bevacqua et al. 2022;Chen et al. 2019;Yin et al. 2023). Nevertheless, the study of compound extreme events still needs to be further deepened and expanded in several aspects. ...
Compound extreme events, such as events with concurrent extreme temperature and precipitation, are often more devastating than single events occurring independently with serious impacts on human society. In this study, we analyzed the future evolution of compound extreme summer days, namely, compound hot–dry days (CHDDs) and compound hot–wet days (CHWDs), in China and explored the relative changes in population and economic exposure based on climate simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6). The results showed that compound extreme days will be more frequent and severe under different scenarios in which the frequency of CHDDs is relatively high with a relatively high growth rate of CHWDs. The frequency of compound extreme days will continue to increase under the SSP2–4.5 and SSP5–8.5 scenarios but decline after 2070 under the SSP1–2.6 scenario. In general, the growth rate of population exposure to moderate/severe CHDDs ranges from 0 to 10%/30 to 50%. Meanwhile, the increasing rate of population exposure to moderate/severe CHWDs ranges from 0 to 30%/30 to 100%. GDP exposure to moderate/severe CHDDs would increase by 0–50%/100–400%, and severe CHWDs increased GDP exposure by more than 800%. Socioeconomic exposure to CHWDs will increase at a faster rate in the future. Due to the increase in compound extreme days and population decline, the relative contribution of climate change to population exposure is larger. Economic development alongside an increase in the number of compound extreme days will contribute relatively more to the interaction of climate and GDP, increasing GDP exposure. This study offers useful insights into mitigation and adaptation measures for compound extreme events and potential climate change in China.
... Arnell 1992;Arnell 2003;Charlton and Arnell 2014;Kay et al. 2021). Uncertainty in the variability of future droughts is determined by changes in precipitation trends as droughts will always coincide with hot extremes relative to the present day as the climate continues to warm (Diffenbaugh et al. 2015;Bevacqua et al. 2022). The timing and sequence of precipitation deficits (e.g. ...
... This, in turn, affects the estimated P R change in D . However, we also note that under 145 such potentially very large changes in P(x) and/or P(y), such changes control the actual change in the probability of concurrent extremes, and dependency changes become irrelevant (Bevacqua et al., 2022). For a thorough assessment of the changes in the dependencies, continuous rather than binary variables X and Y (Bevacqua et al., 2020), as well as larger sample sizes (Bevacqua et al., 2023), would be required. ...
... In general, the changes in the frequency of individual extreme events control the widespread increases in compound events. In contrast, changes in the coupling between extremes appear to have comparably small effects (Fig. 5), which is in line with previous studies (e.g., Bevacqua et al. (2020Bevacqua et al. ( , 2022). The main driver of the projected increase in co-occurrence of river floods and 210 wildfires is the increase in the frequency of river floods by the end of the century under RCP8.5 (Fig. 5a-c). ...
Concurrent extreme climate events exacerbate adverse impacts on humans, the economy, and the environment relative to extremes occurring in isolation. While changes in the frequency of individual extreme events have been researched extensively, changes in their interactions, dependence and joint occurrence have received far less attention, particularly in the East African region. Here, we analyse the joint occurrence of pairs of the following extremes over East Africa: river floods, droughts, heatwaves, crop failures, wildfires and tropical cyclones. We use bias-adjusted impact simulations under past and future climate conditions from the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP). We find an increase in the area affected by pairs of these extreme events, with the strongest increases for joint heatwaves & wildfires (+940 % by the end of the century under RCP6.0 relative to present day), followed by river floods & heatwaves (+900 %) and river floods & wildfires (+250 %). The projected increase in joint occurrences typically outweighs historical increases even under an aggressive mitigation scenario (RCP2.6). We illustrate that the changes in the joint occurrences are often driven by increases in the probability of one of the events within the pairs, for instance heatwaves. The most affected locations in the East Africa region by these concurrent events are areas close to the River Nile and parts of the Congo basin. Our results overall highlight that concurrent extremes will become the norm rather than the exception in East Africa, even under low-end warming scenarios.
