Search

Atmospheric rivers (ARs) significantly impact the hydrological cycle and associated extremes in western continental regions. Recent studies suggest ARs also influence water resources and extremes in continental interiors. AR detection tools indicate that AR conditions are relatively frequent in areas east of the Rocky Mountains. The origin of these ARs, whether from synoptic‐scale waves or mesoscale processes, is unclear. This study uses meteorological composite maps and transects of AR conditions during the four seasons. The analysis reveals that ARs east of the Rockies are associated with long‐wave, baroclinic Rossby waves. This result demonstrates that eastern North American ARs are dynamically similar to their western coastal counterparts, though mechanisms for vertical moisture flux differ between the two. These findings provide a foundation for understanding future climate change and ARs in this region and offer new methods for evaluating climate model simulations. Plain Language Summary: Atmospheric rivers (ARs) are a weather pattern that brings high amounts of atmospheric water and winds in a relatively narrow region. ARs are typically considered a "west coast" phenomenon, largely because the majority of the scientific research on ARs has focused on ARs in western coastal regions: particularly the western United States (US). ARs occur in continental interiors, but there has been some debate about whether these ARs represent the same type of weather as those in western coastal regions. This paper uses two objective methods for identifying ARs and finds times when ARs are present in three locations in the eastern half of the US: Norman, OK, Bloomington, IN, and Washington, DC. Examination of weather conditions during these AR times shows remarkable similarity to conditions associated with west coast ARs. This gives strong evidence that ARs do occur in the eastern half of the US. This result is important because it suggests that ARs may be important for water resources and extreme weather in the eastern half of the US, just as they are in the western US. This result also suggests that ARs may be important for water resources and extremes in other continental interiors. Key Points: Atmospheric rivers (ARs) east of the Rockies are associated with baroclinic wavesWestern coastal ARs and eastern/midwest ARs are dynamically similarSynoptic‐scale uplift, combined with convective instability, provide efficient mechanisms for generating precipitation [ABSTRACT FROM AUTHOR]

Time‐lapse cameras have been widely used as a tool to monitor the timing of seasonal vegetation growth. These simple, relatively inexpensive systems can provide high‐frequency observations of leaf development and demography which are critical data sets needed to characterize plant phenology from species to landscapes. This is important for understanding how plants are responding to global changes, as well as for validating satellite‐derived phenology products.However, in remote regions including the high‐latitude Arctic, deploying time‐lapse cameras could be challenging. The remoteness and lack of widespread power and telecommunications infrastructure limit options for the installation, maintenance and retrieval of data and equipment, and make it difficult for cameras to survive in extreme weather (e.g. long cold winters). To improve our understanding of Arctic phenology, new technologies are required to address these challenges.Here, we present a novel, low‐power, compact, lightweight time‐lapse camera system, called power‐interval camera automation module (PiCAM). The PiCAM was designed with explicit consideration to simplify deployment (i.e. without a need for external power supplies) of camera systems and to address the challenges of camera survival in harsh Arctic environments. In this paper, we describe the design, setup and technical details of the PiCAM and provide a roadmap for how to build and operate these systems. As proof of concept, we deployed 26 PiCAMs at three low‐Arctic tundra sites on the Seward Peninsula, Alaska in early August 2021 for characterizing Arctic plant phenology.Of the 26 PiCAMs, 70% remained active at the point of our revisit in late July 2022 despite the extreme winter temperatures they experienced (< −30°C, heavy snow cover). We extracted key plant phenology metrics from the PiCAMs and captured strong differences across key Arctic plant species. We showed that the PiCAM has the potential to be widely used for monitoring plant phenology across the broader Arctic region, addressing the need for ground‐based understanding of Arctic phenological diversity to develop knowledge of plant response to climate change and to validate remote sensing products. [ABSTRACT FROM AUTHOR]

Over the past twelve years the number of papers that explore the impacts of climate change on biodiversity in the conservation literature has grown on average by 20% annually. By categorising these papers on their primary research questions, we show that the vast majority of these articles (88.6%) focus only on those impacts that arise directly as a result of climate change, ignoring the potentially significant indirect threats that arise from human adaptation responses. This pattern has remained fairly consistent throughout the review period (2000-2012), with a trend towards more articles considering both direct and indirect impacts towards the end of the period. We also find a bias in the time-frames considered by published articles that project future impacts of climate change on biodiversity, with more than three-quarters (77.9%) of papers only considering impacts after 2031, and almost half (49.1%) only considering impacts after 2051. This focus on long-term, direct impacts creates a mismatch, not only with the life-cycles of species and timescales of many ecological processes, but also with most management and policy timelines and the short-term nature of human decision making processes. The focus on studying the long-term, direct impacts of climate change on biodiversity is likely a function of the lack of availability of climate projections on shorter temporal scales; a perception that short-term impacts will be minor; and, insufficient integration with the social and political sciences. While the direct impact of changes in mean climatic conditions will significantly change the biosphere by the end of the century, near term changes in seasonality and extreme events coupled with human adaptation responses are likely to have substantial impacts much sooner, threatening the survival of species and ecosystems. It is therefore essential that we balance our research efforts to facilitate a better understanding of these more imminent threats. [ABSTRACT FROM AUTHOR]

Among several devastating natural hazards, flooding is a common and serious threat to society causing huge loss of lives, properties, and infrastructure throughout the world. The intensity and frequency of this extreme weather event are expected to increase due to significant changes in the present‐day climate and land use and land cover (LULC) pattern. India has a very systematic and organized structural program and policies but lacks proper implementations, and adverse effect of climate change and the extreme event goes on in society. This paper is an analysis of floods in India and hazards due to climate change and LULC change patterns. Three models, namely "Eco‐biogeography‐based optimization (EBO), Random forest (RF), and Support vector machine (SVM)" were used to obtain the final output to prepare a "Flood susceptibility map". The result was validated through the "Receiver operating characteristics (ROC)" with "Area under curve (AUC)" values. The future rainfall scenario has been estimated by considering the "General circulation models" through different "shared socioeconomic pathways (SSPs)". The values of AUC are 0.915 (EBO), 0.887 (RF), and 0.869 (SVM), respectively. After consideration of different SSPs, the result shows that there is an increasing tendency of flood hazards in the projected period. Among all the employed modelling approaches, the EBO model has notable potential in delineating the possible flood‐prone regions for effective flood planning and management. Decision‐makers can benefit from country‐specific information and regional planner to implement sustainable and long‐term measures to overcome this type of hazardous situation. [ABSTRACT FROM AUTHOR]

The frequency with which tropical cyclones (TCs) occur controls all other aspects of tropical cyclone risk since a storm that does not occur can do no harm. Yet this frequency is poorly understood. There is no accepted theory that explains the average number of TCs that occur each year on the Earth, nor how that number will change with global warming. Arguments based on global budgets of heat or moisture do not yet appear helpful, nor does a detailed understanding of the physical processes of TC genesis. Empirical indices that predict TC frequency as a function of large‐scale environmental variables can explain some of its relative variations in space and time, but not its absolute value. Global numerical models with horizontal grid spacings on the order of 25–50 km have allowed much improved simulations of TC activity, however. Many such models project a decrease in frequency with warming, but some project an increase. Idealized simulations, including those at higher resolutions, offer promise by allowing a systematic, deductive investigation of the roles of individual environmental factors. In addition to the larger‐scale environmental modulation of genesis likelihood, precursor disturbances, or "seeds", may exert an independent influence on TC frequency. Plain Language Summary: The term tropical cyclone frequency refers to the average number of tropical cyclones (also known as hurricanes, typhoons, etc.) which occur each year, either over the earth as a whole or in smaller regions. In this paper, the authors review the state of the science regarding what is known about tropical cyclone frequency. The state of the science is not great. There are around 80 tropical cyclones in a typical year, and we do not know why it is this number and not a much larger or smaller one. We also do not know much about whether this number should increase or decrease as the planet warms‐‐‐thus far, it has not done much of either on the global scale, though there are larger changes in some particular regions. No existing theory predicts tropical cyclone frequency. In this situation, we are left with numerical models as our primary tool, and the authors discuss the strengths, weaknesses, and different ways of using such models to investigate tropical cyclone frequency. Idealized simulations, in which the planet is made simpler than it really is, are allowing some new insights. Another promising avenue of investigation involves studying the weaker disturbances that sometimes strengthen into tropical cyclones. Key Points: We do not understand why the number of tropical cyclones per year is what it is, nor how it may be changingIn the absence of theory, our main tools are numerical modelsPromising research directions include idealized simulations at high resolution and study of precursor disturbances, or "seeds" [ABSTRACT FROM AUTHOR]

Climate extremes, such as severe drought, heat waves and periods of heavy rainfall, can have profound consequences for ecological systems and for human welfare. Global climate change is expected to increase both the frequency and the intensity of climate extremes and there is an urgent need to understand their ecological consequences. Major challenges for advancing our understanding of the ecological consequences of climate extremes include setting a climatic baseline to facilitate the statistical determination of when climate conditions are extreme, having sufficient knowledge of ecological systems so that extreme ecological responses can be identified, and finally, being able to attribute a climate extreme as the driver of an extreme ecological response, defined as an extreme climatic event (ECE). The papers in this issue represent a cross-section of the emerging field of climate extremes research, including an examination of the palaeo-ecological record to assess patterns and drivers of extreme ecological responses in the late Quaternary, experiments in grasslands assessing a range of ecological responses and the role of ecotypic variation in determining responses to climate extremes, and the quantification of the ecological consequences of a recent ECE in the desert Southwest of the USA. Synthesis. The papers in this Special Feature suggest that although the occurrence of ECEs may be common in palaeo-ecological and observational studies, studies in which climate extremes have been experimentally imposed often do not result in ecological responses outside the bounds of normal variability of a system. Thus, ECEs occur much less frequently than their potential drivers and even less frequently than observational studies suggest. Future research is needed to identify the types and time-scales of climate extremes that result in ECEs, the potential for interactions among different types of climate changes and extremes, and the role of genetic, species and trait diversity in determining ecological responses and their evolutionary consequences. These research priorities require the development of alternative research approaches to impose realistic climate extremes on a broad range of organisms and ecosystems. [ABSTRACT FROM AUTHOR]

Against an academic and policy backdrop of interest in (and concerns about) the issue, this paper draws on a range of academic writing in various disciplines to explore visual strategies of climate change communication. The geographic scope of the investigation is the United Kingdom, with particular attention to recognizable icons of climate change in UK media and the images used in political campaigns. The paper is in two parts. The first part concentrates on various efforts to put a 'face' on the climate change issue, while part two suggests that weather and renewable energy are the dominant alternative motifs. The paper draws a basic distinction between fear-laden representations of climate change and a variety of visual efforts to use so-called inspirational imagery. All of the images reviewed suggest an affirmative answer to the question in the title, there are multiple efforts underway to move beyond polar bears and represent climate change in more creative and meaningful ways. The bigger question addressed is one raised already by photographers as well as academics, i.e. whether documentary photography (rather than particular types of images) is the more fundamental issue. The answer in the paper is that photographs are no different from other visual images in their capacity to draw attention to messages. The challenge is to use visuals creatively, in ways that prompt positive engagement with climate change without enhancing public disengagement and fatalism. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

All nature relies on water, yet climate change threatens water availability to the highest degree—from too much (e.g. extreme weather; flooding) to too little (e.g. droughts; wildfires). These water shifts threaten all life on earth.Societies' safe and reliable water accessibility faces growing uncertainty from climate change; however, water crisis communication may inadvertently remind audiences of their mortality. According to terror management theory, these mortality reminders can hinder pro‐environmental efforts in humans and even increase intergroup biases—a significant challenge for developing environmental solutions. While climate change has been examined as a mortality reminder, water remains untested.We presented participants with either a mortality‐laden message, an aversive but not‐life‐threatening message, or one of three threatening water‐related messages—experiencing drowning, dehydration or contaminated water consumption—to determine if the water‐related messages function similarly to the mortality message.Some (e.g. drowning; contaminated water), but not all (e.g. dehydration), water messages increased death‐thought accessibility, which could lead to paradoxical environmental behaviours, depending on the audience. Our research findings should inform policymakers, non‐profit organizations and other water correspondents' communication strategies.As some threatening water messages elicit similar responses to known mortality reminders, the way water crises are framed is important for water‐related decision‐making and ensuring equitable, successful pro‐environmental outcomes. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

With ongoing climate change and the increase in extreme weather events, especially droughts, the challenge of maintaining food security is becoming ever greater. Locally adapted landraces of crops represent a valuable source of adaptation to stressful environments. In the light of future droughts—both by altered soil water supply and increasing atmospheric water demand (vapor pressure deficit [VPD])—plants need to improve their water efficiency. To do so, plants can enhance their access to soil water by improving rhizosphere hydraulic conductivity via the exudation of mucilage. Furthermore, plants can reduce transpirational water loss via stomatal regulation. Although the role of mucilage and stomata regulation on plant water management have been extensively studied, little is known about a possible coordination between root mucilage properties and stomatal sensitivity as well as abiotic drivers shaping the development of drought resistant trait suits within landraces. Mucilage properties and stomatal sensitivity of eight Mexican landraces of Zea mays in contrast with one inbred line were first quantified under controlled conditions and second related to water demand and supply at their respective site of origin. Mucilage physical properties—namely, viscosity, contact angle, and surface tension—differed between the investigated maize varieties. We found strong influences of precipitation seasonality, thus plant water availability, on mucilage production (R2 =.88, p <.01) and mucilage viscosity (R2 =.93, p <.01). Further, stomatal sensitivity to increased atmospheric water demand was related to mucilage viscosity and contact angle, both of which are crucial in determining mucilage's water repellent, thus maladaptive, behavior upon soil drying. The identification of landraces with pre‐adapted suitable trait sets with regard to drought resistance is of utmost importance, for example, trait combinations such as exhibited in one of the here investigated landraces. Our results suggest a strong environmental selective force of seasonality in plant water availability on mucilage properties as well as regulatory stomatal effects to avoid mucilage's maladaptive potential upon drying and likely delay critical levels of hydraulic dysfunction. By this, landraces from highly seasonal climates may exhibit beneficial mucilage and stomatal traits to prolong plant functioning under edaphic drought. These findings may help breeders to efficiently screen for local landraces with pre‐adaptations to drought to ultimately increase crop yield resistance under future climatic variability. [ABSTRACT FROM AUTHOR]

Body condition is a frequently used physiological indicator of avian health and can be affected by an array of environmental variables. Although a number of studies have investigated the specific effects of individual weather variables on body condition in birds, few have analyzed the effects of both temperature and precipitation within the context of an extreme weather event such as hurricanes. In this study, we examined the relationship between breeding‐season body condition and daily maximum temperature, daily minimum temperature, and monthly total precipitation for three passerine bird species at the Welder Wildlife Refuge near Rockport, Texas. We also evaluated yearly changes in body condition over a 12‐year period for northern cardinals (Cardinalis cardinalis), painted buntings (Passerina ciris), and white‐eyed vireos (Vireo griseus), focusing on the extreme precipitation event of Hurricane Harvey, which caused heavy localized flooding. We found that body condition declined with average daily minimum and maximum temperatures, while precipitation had varied, species‐specific effects in the three species analyzed. Our results also suggest that northern cardinals experienced a notable reduction in average body condition in the 2 years following Hurricane Harvey. Taken together, we conclude that short‐term precipitation and temperature drivers can be important correlates of body condition in songbirds and that severe weather events may reduce body condition in some bird species. [ABSTRACT FROM AUTHOR]

The current study extends earlier work that demonstrated future extratropical transition (ET) events will feature greater intensity and heavier precipitation to specifically consider potential changes in the impacts of landfalling ET events in a warming climate. A quasi‐idealized modeling framework allows comparison of highly similar present‐day and future event simulations; the model initial conditions are based on observational composites, increasing representativeness of the results. The future composite ET event features substantially more impactful weather conditions in coastal areas, with heavier precipitation and greater storm intensity. Specifically, a Category 2 present‐day storm attained Category 4 Saffir‐Simpson intensity in the future simulation and maintained greater intensity throughout the entire life cycle, although the storm undergoes less reintensification during the post‐ET process, a result of reduced baroclinic conversion. These findings suggest increased potential for coastal hazards due to stronger tropical cyclone winds and heavier rainfall, leading to more severe coastal flooding and storm surge. Plain Language Summary: Earlier studies demonstrate that climate change can amplify the strong winds and heavy rainfall accompanying tropical cyclones (TCs) that are undergoing transformation into midlatitude cyclones. The current study extends earlier work, which focused on oceanic TCs, to specifically consider potential changes in the impacts of landfalling transformation events in a warming climate. The future events feature substantially more impactful weather conditions in coastal areas with heavier rainfall and greater storm intensity. In particular, we find that a Saffir‐Simpson Category 2 tropical storm in present‐day conditions becomes a Category 4 storm in the future, resulting in more extreme weather conditions along high‐latitude coastlines throughout its entire life cycle, even though the storm undergoes less reintensification after it completes the transformation, due to reduced future temperature contrasts in the lower atmosphere The possibility of compound coastal hazards, including stronger winds, lower central pressure, and heavier rainfall, also indicates a heightened risk of coastal flooding and storm surges. Key Points: Substantially stronger winds attributed to the intensified transitioning storm are evident, impacting the U.S. East Coast in the futurePrecipitation analysis features substantial future increases in total rainfall associated with the transitioning storm along the East CoastIn the innermost storm core region, rainfall increased at a rate more than double that predicted by Clausius‐Clapeyron scaling [ABSTRACT FROM AUTHOR]

This special issue of GeoHealth, entitled Rhythms of the Earth: Ecological Calendars and Anticipating the Anthropogenic Climate Crisis, is a transdisciplinary articulation of a methodology of hope to confront the multiple injustices of the Anthropocene. One of the greatest challenges of the climate crisis is the lack of predictability at the scale of communities where impacts are most immediate. Indigenous and rural societies face an ever shifting "new normal" through increasing inconsistency in the seasonality of temperature and precipitation, as well as greater frequency of extreme weather events. With global food systems dependent on local and small producers, climatic variability disrupts access to affordable, nutritious, and culturally relevant food. Ecological calendars are context‐specific knowledge systems grounded in a particular cultural milieu and ecological space, that build anticipatory capacity for seasonal change. They measure and give meaning to time. Based on close observation of one's habitat, human societies have used such calendars for hundreds of years and potentially millennia. By engaging with the interactions among physical phenomena (such as the first snowfall or last frost) and biological events (such as blossoming of specific trees, arrival of migratory birds or mammals, appearance of plants or insects), human societies have been able to identify optimal time windows for their livelihood activities. The 11 research articles in Rhythms of the Earth cover a considerable geographical breadth from Africa to the Arctic; and, from North and South America to Central Asia. They provide evidence that spans millennia from the Roman Empire to the contemporary Anthropocene. Key Points: Rhythms of the Earth is a transdisciplinary collaboration between Indigenous Knowledge and ScienceIn Rhythms of the Earth , an innovative culturally and ecologically grounded way to anticipate seasonal change is proposedSignificant diversity of thought from around the world is engaged in Rhythms of the Earth because the research articles are co‐authored by artists, Indigenous community members, and scholars in the biological, physical, and social sciences as well as the humanities [ABSTRACT FROM AUTHOR]

Heatwaves are an increasingly common extreme weather event across the globe and are projected to surge in frequency and severity in the coming decades. Plant‐pollinator mutualisms are vulnerable due to interacting effects of extreme heat on insect pollinator foraging behaviour and their forage plants.We designed an experiment to parse the impact of extreme heat on bumblebee foraging mediated directly through air temperature and indirectly through changes in plant rewards.Temperatures simulating a moderate heatwave negatively impacted foraging bumblebees reducing the proportion of successful foraging bouts, foraging bout duration and plant and flower visitation and indirect stress through reduced nectar production that limited foraging bout duration.Our experimental results provide a mechanistic link between climate, plants and pollinators and suggest in situ conditions from heatwaves could have profound negative consequences for bumblebee colony persistence and maintenance of pollination services. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Rise in mean temperature put a great deal of uncertainty about how weather and climate extremes may play out, particularly in India's varied climatic zones. Consequently, it is important to understand the possible changes in both magnitude and direction of weather and climate extremes like rainfall for different warming levels of 1.5 and 2°C scenarios concerning preindustrial and present levels. Hence in the present study, the precipitation behavior of seven North Indian states that is, Haryana, Himachal Pradesh, J&K, Punjab, Rajasthan, Uttar Pradesh, and Uttarakhand carefully studied using CMIP5 models. Future projections of precipitation has been done for the Paris Agreement global warming level of 1.5 and 2°C scenarios. Along with model validation and future projections of precipitation, the return period of extreme rainfall is also discussed to understand the behavior of the occurrence of extreme precipitation. Statistical analysis shows that the ensemble means have the least error as compared to the other six CMIP5 models. Therefore, future analysis has been done with the ensemble mean. Our findings show that the precipitation is likely to decrease in the 1.5°C scenarios, while it is likely to increase in the 2°C scenarios. The occurrence and intensity of extreme rainfall events are likely to be more frequent in all the models. The return period of the extreme rainfall events is likely to increase in all the states in both the warming scenarios. A three‐fold rise is likely to increase extreme rainfall events in the 2°C scenario. Key Points: Study performs a detailed analysis of rainfall behavior of the northern states India during preindustrial, present, 1.5 and 2° scenariosSix climate models were selected out of 26 CMIP5 climate models based on the capability of representing the monsoon rainfall over IndiaIn the 2°C scenario, the recurrence period for intense rainfall events will likely to increase by a factor of 3 [ABSTRACT FROM AUTHOR]

Climate change is increasing the intensity, duration, and frequency of extreme climate events (ECEs). These ECEs can have major ecological consequences, e.g., changing nutrient flows, causing extirpation, and altering organismal development. Many ECEs are discrete events that occur at distinctive times during the biological processes they impact. Because of this, ECEs are likely to have differing ecological impacts depending on when they happen, yet we lack on studies that explore how the ecological consequences of ECEs vary with when they occur. Drawing upon evidence from physiological, population, and community ecology, and previous work on ecological disturbances, we suggest that the consequences of ECEs will be sensitive to when they occur. We illustrate the importance of timing by showing how the effects of an ECE could vary depending on when it occurs through the course of (1) organismal ontogeny, (2) population dynamics, and (3) community assembly. An enhanced focus on the timing of extreme weather in climate change research will reveal how and when ECEs are altering ecosystems, possible mechanisms behind these impacts, and what ecosystems or species are most vulnerable to ECEs, helping us to make more informed predictions about the ecological consequences of climate change. [ABSTRACT FROM AUTHOR]

The El Niño Southern Oscillation (ENSO) impacts climate variability globally and can influence extreme climate and weather events. We quantify the uncertainty in ENSO's atmospheric teleconnections with extremes using the Twentieth Century Reanalysis, showing that uncertainty estimates vary regionally over the historical period. Uncertainty is found to be greater in regions of lower socioeconomic development. This can be linked to the limited availability of observational data in these regions as well as difficulties constraining tropical climate dynamics in global gridded atmospheric data sets. Poorer locations face greater challenges due to lack of understanding of past variability limiting confidence in regional projections. Plain Language Summary: Extreme weather events, such as droughts and floods, can be influenced by climate phenomena such as the El Niño Southern Oscillation. El Niño and La Niña events are the biggest drivers of climate variability globally and so it is important to understand their influence on climate extremes. We demonstrate that understanding of how El Niño and La Niña influence extremes is not consistent across the globe. There is the least understanding in the poorest regions of the world. As many of these regions are especially vulnerable to climate change, this has important implications for adapting to the impacts of extremes. Key Points: Uncertainty in historical El Niño Southern Oscillation teleconnections is examined using an ensemble reanalysis productRegional climate responses to El Niño and La Niña are more uncertain in poorer regionsThis inequality in climate information must be addressed to increase resilience to extremes [ABSTRACT FROM AUTHOR]

Extreme precipitation events severely affect ecosystems and human society. While most existing studies investigated either their temporal changes or spatial extent, the joint behaviors in both time and space are neglected. Here, we examine different evolution patterns of spatiotemporally contiguous precipitation events (SCEPEs) across China during 1997–2021 from a three‐dimensional (3D, latitude × longitude × time) perspective. The SCEPEs exhibit distinct behaviors in different subregions. The SCEPEs in northwestern areas have relatively longer moving distances and weaker magnitude, mostly originating from the west and traveling to the east. Southeastern events display stronger magnitudes and travel at shorter distances, characterized by a more localized phenomenon. Since 1997, the frequency of SCEPEs in China has nearly doubled, their magnitude and affected areas have increased, but the moving distance and speed have decreased. Our findings provide important references for predicting extreme weather events and mitigating their detrimental impacts. Plain Language Summary: Extreme precipitation events have serious impacts on human society and ecosystems, but their evolution behaviors in both time and space dimensions are not understood. For the first time, here we study the "true" 3D (latitude × longitude × time) structures and evolution patterns of spatiotemporally contiguous extreme precipitation events (SCEPEs) across China that occur synchronously in neighboring regions or consecutively in adjacent days. The results show that SCEPEs in China exhibit distinct behaviors in different locations and time periods. Spatially, the SCEPEs in northern China move eastward at faster speeds and longer distances than southern ones, which tend to direct to all directions and show local features. Temporally, SCEPEs have been significantly intensified from 1997 to 2021, in terms of increased frequency, magnitude, and affected areas, and decreased moving distance and moving speed. Our findings from a 3D perspective offer new scientific references for forecasting and adapting precipitation extremes and their resultant devastating disasters. Key Points: The 3D evolution properties of spatiotemporally contiguous extreme precipitation events (SCEPEs) in China are examined for the first timeNorthern SCEPEs move eastward and faster at longer distance than southern ones, which tend to be from all directions and show local featuresThe moving distance and speed of SCEPEs have declined, but their frequency, magnitude, and area have increased since late 1990s [ABSTRACT FROM AUTHOR]

Instrumental weather records (1880–2020s) from eastern North America were analyzed to characterize the regional patterns and drivers of seasonal extreme weather (snow, rain, high and low temperatures). Using agglomerative hierarchical clustering of extreme weather data, the region was divided into three subregions that are influenced by coastal‐marine gradients and latitudinal factors. Subsequent analyses were performed on high‐quality stations from each subregion and results compared between one another. Long‐term locally weighted linear regressions delineated long‐term changes in extreme weather, and a combination of spectral analysis, continuous wavelet transforms, and cross wavelet transforms were used to identify periodic components in the data. Regional extreme weather is generally periodic, composed of interannual to interdecadal‐scale oscillations and driven by several natural climatic oscillations. The most important such oscillation is the 11‐year Schwabe Solar Cycle, which has a strong and continuous effect on regional extreme weather. The Pacific Decadal Oscillation and Quasi Biennial Oscillation also show considerable influence, but intermittently. The El Niño Southern Oscillation, the Arctic Oscillation, and the North Atlantic Oscillation all have a weaker but interrelated influence. While the Atlantic Multidecadal Oscillation showed the weakest overall influence on regional extreme weather, it demonstrated a clear spatial gradient across the region, unlike the aforementioned oscillations. Long‐term changes in regional extreme weather are not generally important, in that a sustained increase or decrease in extreme weather events is not usually characteristic of the weather records. The primary exception to this result is for extreme minimum temperature events, whose frequency has slightly decreased since the 1880s. Key Points: Extreme weather events across eastern North America from 1881 to 2020 were analyzed for trends and patternsEastern North America exhibits three distinct extreme weather subregionsCyclic patterns in extreme weather were attributed to various large‐scale climate oscillations [ABSTRACT FROM AUTHOR]

It sounds straightforward. As the Earth warms due to the increased concentration of greenhouse gases in the atmosphere, global temperatures rise and so heatwaves become warmer as well. This means that a fixed temperature threshold is passed more often: the probability of extreme heat increases. However, land use changes, vegetation change, irrigation, air pollution, and other changes also drive local and regional trends in heatwaves. Sometimes they enhance heatwave intensity, but they can also counteract the effects of climate change, and in some regions, the mechanisms that impact on trends in heatwaves have not yet been fully identified. Climate models simulate heatwaves and the increased intensity and probability of extreme heat reasonably well on large scales. However, changes in annual daily maximum temperatures do not follow global warming over some regions, including the Eastern United States and parts of Asia, reflecting the influence of local drivers as well as natural variability. Also, temperature variability is unrealistic in many models, and can fail standard quality checks. Therefore, reliable attribution and projection of change in heatwaves remain a major scientific challenge in many regions, particularly where the moisture budget is not well simulated, and where land surface changes, changes in short‐lived forcers, and soil moisture interactions are important. Plain Language Summary: Heatwaves are arguably the most deadly weather phenomena. As the Earth warms due to higher concentrations of greenhouse gases, one would expect heatwaves to become worse as well, killing even more people unless they are better protected against the heat. However, it turns out that the world is not so simple and that many other factors also influence heatwaves. Land use changes, irrigation, air pollution, and other changes also drive trends in heatwaves. Some of these cause much larger trends while some have counteracted the climate change‐driven trends up to now. In some regions, the causes of high trends have not yet been identified. Current generation climate models often do not simulate all these mechanisms correctly so will have to be improved before we can more confidently trust their description of past trends and projections of future trends in heatwaves. Key Points: The IPCC AR6 WG1 states the "frequency and intensity of hot extremes have increased"The IPCC notes that the effect of increased greenhouse gas on high temperatures is moderated or amplified at local scales by other factorsConfident quantitative attribution statements of the human influence on heatwaves are limited by our understanding of these local processes [ABSTRACT FROM AUTHOR]

Low-likelihood weather events can cause dramatic impacts, especially when they are unprecedented. In 2020, amongst other high-impact weather events, UK floods caused more than £300 million damage, prolonged heat over Siberia led to infrastructure failure and permafrost thawing, while wildfires ravaged California. Such rare phenomena cannot be studied well from historical records or reanalysis data. One way to improve our awareness is to exploit ensemble prediction systems, which represent large samples of simulated weather events. This ‘UNSEEN’ method has been successfully applied in several scientific studies, but uptake is hindered by large data and processing requirements, and by uncertainty regarding the credibility of the simulations. Here, we provide a protocol to apply and ensure credibility of UNSEEN for studying low-likelihood high-impact weather events globally, including an open workflow based on Copernicus Climate Change Services (C3S) seasonal predictions. Demonstrating the workflow using European Centre for Medium- Range Weather Forecasts (ECMWF) SEAS5, we find that the 2020 March–May Siberian heatwave was predicted by one of the ensemble members; and that the record-shattering August 2020 California-Mexico temperatures were part of a strong increasing trend. However, each of the case studies exposes challenges with respect to the credibility of UNSEEN and the sensitivity of the outcomes to user decisions. We conclude that UNSEEN can provide new insights about low-likelihood weather events when the decisions are transparent, and the challenges and sensitivities are acknowledged. Anticipating plausible low likelihood extreme events and uncovering unforeseen hazards under a changing climate warrants further research at the science-policy interface to manage high impacts. [ABSTRACT FROM AUTHOR]

Understanding the evolution of heatwaves is important for their prediction, mitigation, and adaptation. While most studies focused on either their temporal variability at individual station (or grid point) or the spatial variation over fixed durations, their daily joint evolution over space and time remains largely unexplored. Here, we investigate multi‐dimensional characteristics of spatiotemporally contiguous heatwaves across China during 1961–2018 using observational data from a 3D perspective (i.e., latitude × longitude × time). Results obtained by the 3D identification show that large contiguous heatwaves in China exhibit distinct characteristics in different geographical locations and time periods. Heatwaves in northern areas prefer to move from west to east at a faster speed, persist longer, and have greater extent and intensity than southern heatwaves, which are generally originated from the east and move westward. It is also found that contiguous heatwaves are growing in frequency, magnitude, areal extent, duration, and traveling distance across China. Plain Language Summary: Known as episodes with temperature exceeding a certain threshold, heatwaves exert severe detrimental impacts on human health. Understanding their joint evolution at both temporal and spatial dimensions is beneficial for us to mitigate the adverse effects and adapt ourselves to future heatwave increases under global warming. However, previous studies mainly focused on either the temporal or spatial changes of heatwaves rather than their co‐variability over both time and space. Here we introduce a new method, the 3D connected component algorithm, to track the 3D evolution of spatiotemporally contiguous heatwaves over China during 1961–2018 using observational data. We find that contiguous heatwaves over northern China prefer to move eastward at a faster speed, persist longer, and have greater extent and intensity than southern heatwaves, which are generally originated from the east and move westward. Contiguous heatwaves show significant increases in frequency, magnitude, coverage, duration, and traveling distance. Key Points: True 3D structure and spatiotemporal evolution of large contiguous heatwave over China are tracked by the 3D connected component labeling algorithmContiguous heatwaves in China exhibit distinct characteristics and evolution patterns in different geographical locations and time periodsSubstantial increases are observed in the frequency, area, magnitude, duration, and moving distance of contiguous heatwaves since the 1960s [ABSTRACT FROM AUTHOR]

The atmospheric river (AR) frequency trends over the Southern Hemisphere are investigated using three reanalyses and two Community Earth System Model (CESM) ensembles. The results show that AR frequency has been increasing over the Southern Ocean and decreasing over lower latitudes in the past four decades and that ARs have been shifting poleward. While the observed trends are mostly driven by the poleward shift of the westerly jet, fully coupled CESM experiments indicate anthropogenic forcing would result in positive AR frequency trends over the Southern Ocean due mostly to moisture changes. The difference between the observed trends and anthropogenically driven trends can be largely reconciled by the atmosphere‐only CESM simulations forced by observed sea surface temperatures: Sea surface temperature variability characteristic of the negative phase of the Interdecadal Pacific Oscillation strongly suppresses the moisture‐driven trends while enhances the circulation‐induced trends over the Southern Ocean, thus bringing the simulated trends into closer agreement with the observed trends. Plain Language Summary: Atmospheric rivers (ARs) are "rivers" in the sky that carry a huge amount of water vapor equivalent to the world's largest rivers on the ground. Because of the amount of water vapor they carry, ARs can cause extreme rainfall and floods upon landfall when the moisture is condensed out by mountain barriers or other favorable conditions. Most of the studies so far have focused on ARs in the Northern Hemisphere. In this study, we found that ARs in the Southern Hemisphere have been occurring at increasingly higher‐latitude regions in the past four decades and that this observed trend is mostly due to winds getting stronger at higher‐latitude regions in the Southern Hemisphere. Using results from climate model simulations, we show that the observed AR trends in the Southern Hemisphere are driven by both human activities, such as greenhouse gas increases and ozone depletion, and the internal variability of sea surface temperatures due to the coupled atmosphere‐ocean system. The poleward shift of ARs in the Southern Hemisphere may have major implications for the amount of moisture and heat transported into Antarctica, thus may also have profound impacts on the Antarctic and in turn, global climate. Key Points: Atmospheric rivers (ARs) have shifted poleward in the Southern Hemisphere over the past four decadesAnthropogenic forcing evidently plays a role in this poleward shift of ARsInterdecadal sea surface temperature variability strongly modulates this poleward shift [ABSTRACT FROM AUTHOR]

Evidence for intensifying rainfall extremes has not translated into "actionable" information needed by engineers and risk analysts, who are often concerned with very rare events such as "100‐year storms." Low signal‐to‐noise associated with such events makes trend detection nearly impossible using conventional methods. We use a regional aggregation approach to boost this signal‐to‐noise, showing that such storms have increased in frequency over much of the conterminous United States since 1950, a period characterized by widespread hydrologic infrastructure development. Most of these increases can be attributed to secular climate change rather than climate variability, and we demonstrate potentially serious implications for the reliability of existing and planned hydrologic infrastructure and analyses. Though trends in rainfall extremes have not yet translated into observable increases in flood risks, these results nonetheless point to the need for prompt updating of hydrologic design standards, taking into consideration recent changes in extreme rainfall properties. Plain Language Summary: Numerous studies have shown that heavy rainfall in the United States and elsewhere is becoming more common and more severe in a warming climate. These studies have not shown, however, how the most extreme rainfall events are changing, since these storms are so rare that they are difficult to assess using conventional techniques, which generally focus on changes at individual geographic locations. We instead use a simple aggregation technique to "pool" multiple observations within a region. This "pooling" allows us to show that rainfall events that exceed common engineering design criteria, including 100‐year storms, have increased in frequency in most parts of the United States since 1950—a period of widespread infrastructure construction. We show that in most locations, these increases are likely due to climate warming. We also show that much of the existing and planned hydrologic infrastructure in the United States based on published rainfall design standards is and will continue to underperform its intended reliability due to these rainfall changes. Key Points: Conventional analyses neglect trends in extreme rainfall events such as the 100‐year storm, which are critical for engineering designA regional aggregation approach reveals significant trends in very extreme rainfall in the United States, mainly due to climate warmingExisting hydrologic infrastructure and analyses in much of the United States may be underperforming due to increases in storm activity [ABSTRACT FROM AUTHOR]

Motivated by the need for cities to prepare for and adapt to climate change, we advance the paradigm of safe‐to‐fail by focusing on the decision dilemmas and the consideration of infrastructure failure consequences in developing infrastructure. Infrastructures are largely designed as fail‐safe; that is, they are not intended to fail, and when failure happens, the consequences are severe. Safe‐to‐fail has been recently presented as the antithesis of fail‐safe, without any specific guidance of what the paradigm is or how to apply it. There is an emerging need for stakeholders, including policy makers, planners, engineers, utilities, and communities to understand infrastructure failures, bring their knowledge into the infrastructure development process, and help adapt cities to unpredictable and changing climate risks. We frame safe‐to‐fail as an infrastructure development paradigm that internalizes the consequences of infrastructure failure in the development process. This framing of safe‐to‐fail further reveals an emerging "infrastructure trolley problem" where the adaptive capacity of some regions is improved at the expense of others. We demonstrate practical dilemmas in developing infrastructure under nonstationary climate and guide managing trade‐offs in the prioritization of different consequences of infrastructure failure. Key Points: Safe‐to‐fail infrastructure are designed to lose function in controlled ways, as failure consequences are incurred by prioritized decisionsThe new framing of safe‐to‐fail paradigm reveals the decision dilemma of infrastructure trolley problemClimate change adaptation via resilient infrastructure development must include multi‐stakeholder's knowledge about various failure impacts [ABSTRACT FROM AUTHOR]

Aim To assess the usefulness of combining climate predictors with additional types of environmental predictors in species distribution models for range-restricted species, using common correlative species distribution modelling approaches. Location Florida, USA Methods We used five different algorithms to create distribution models for 14 vertebrate species, using seven different predictor sets: two with bioclimate predictors only, and five 'combination' models using bioclimate predictors plus 'additional' predictors from groups representing: human influence, land cover, extreme weather or noise (spatially random data).We use a linear mixed-model approach to analyse the effects of predictor set and algorithm on model accuracy, variable importance scores and spatial predictions. Results Regardless of modelling algorithm, no one predictor set produced significantly more accurate models than all others, though models including human influence predictors were the only ones with significantly higher accuracy than climate-only models. Climate predictors had consistently higher variable importance scores than additional predictors in combination models, though there was variation related to predictor type and algorithm. While spatial predictions varied moderately between predictor sets, discrepancies were significantly greater between modelling algorithms than between predictor sets. Furthermore, there were no differences in the level of agreement between binary 'presence-absence' maps and independent species range maps related to the predictor set used. Main conclusions Our results indicate that additional predictors have relatively minor effects on the accuracy of climate-based species distribution models and minor to moderate effects on spatial predictions. We suggest that implementing species distribution models with only climate predictors may provide an effective and efficient approach for initial assessments of environmental suitability. [ABSTRACT FROM AUTHOR]

Growing recognition of the importance of climate extremes as drivers of contemporary and future ecological dynamics has led to increasing interest in studying these locally and globally important phenomena. Many ecological studies examining the impacts of what are deemed climate extremes, such as heat waves and severe drought, do not provide a definition of extremity, either from a statistical context based on the long-term climatic record or from the perspective of the response of the system - are the effects extreme (unusual or profound) in comparison to normal variability? A synthetic definition of an extreme climatic event (ECE) is proposed that includes 'extremeness' in both the driver and the response: an ECE is as an episode or occurrence in which a statistically rare or unusual climatic period alters ecosystem structure and/or function well outside the bounds of what is considered typical or normal variability. This definition is accompanied by a mechanistic framework based on the concept that extreme response thresholds associated with significant community change and altered ecosystem function must be crossed in order for an ECE to occur. Synthesis. A definition and mechanistic framework for ECEs is used to identify priorities for future research that will enable ecologists to more fully assess the ecological consequences of climate extremes for ecosystem structure and function today and in a future world where their frequency and intensity are expected to increase. [ABSTRACT FROM AUTHOR]

Public lands provide many ecosystem services and support diverse plant and animal communities. In order to provide these benefits in the future, land managers and policy makers need information about future climate change and its potential effects. In particular, weather extremes are key drivers of wildfires, droughts, and false springs, which in turn can have large impacts on ecosystems. However, information on future changes in weather extremes on public lands is lacking. Our goal was to compare historical (1950–2005) and projected mid‐century (2041–2070) changes in weather extremes (fire weather, spring droughts, and false springs) on public lands. This case study looked at the lands managed by the U.S. Forest Service across the conterminous United States including 501 ranger district units. We analyzed downscaled projections of daily records from 19 Coupled Model Intercomparison Project 5 General Circulation Models for two climate scenarios, with either medium‐low or high CO2− equivalent concentration (RCPs 4.5 and 8.5). For each ranger district, we estimated: (1) fire potential, using the Keetch‐Byram Drought Index; (2) frequency of spring droughts, using the Standardized Precipitation Index; and (3) frequency of false springs, using the extended Spring Indices. We found that future climates could substantially alter weather conditions across Forest Service lands. Under the two climate scenarios, increases in wildfire potential, spring droughts, and false springs were projected in 32–72%, 28–29%, and 13–16% of all ranger districts, respectively. Moreover, a substantial number of ranger districts (17–30%), especially in the Southwestern, Pacific Southwest, and Rocky Mountain regions, were projected to see increases in more than one type of weather extreme, which may require special management attention. We suggest that future changes in weather extremes could threaten the ability of public lands to provide ecosystem services and ecological benefits to society. Overall, our results highlight the value of spatially‐explicit weather projections to assess future changes in key weather extremes for land managers and policy makers. [ABSTRACT FROM AUTHOR]