Above-average Temperatures Research Articles

Evaluation of deforestation, climate change and CO2 emissions in the Amazon biome using the Moran Index

Since the 1990s, the Amazon has been undergoing a severe occupation process, causing a significant increase in deforestation. This occupation occurs for various reasons, such as the expansion of agricultural areas and the extraction of raw materials, mainly through predatory logging. These factors are responsible for causing various impacts, such as an increase in Greenhouse Gas (GHG) emissions and changes in climate variables. In this context, the main objective of this work is to evaluate deforestation in the Amazon, verifying whether this problem is correlated with CO2 emission data and temperature increase, for the municipalities belonging to the biome. To this end, Moran's Index was calculated for the variables studied, and subsequently Moran's scatter diagram, significance map (LISA MAP) and Local Moran's Index map (LISA Cluster map) were generated to verify the correlations between these variables over the years. The results visualized by processing the Moran Index show that there is a high positive correlation between deforestation and CO2 emissions, especially in the municipalities located in the “arc of deforestation". With regard to the temperature variable, Moran's Index indicated that municipalities with high rates of deforested area are the same municipalities that have above-average temperature values. Finally, the work shows that the Moran's Index tool is efficient and satisfactory for data analysis and that the methodology and information provided through it can be applied to other studies and different databases, and can help decision-makers create strategies to combat and control deforestation and other problems in various regions of the country and the world.

Dendrochronology and extreme climate signals recorded in seven Icelandic shrubs: A multi-species approach in the sub-Arctic

Iceland, located in the climatologically sensitive subarctic zone, is one of the key areas for studying climate change and the current Arctic warming. Poor and rich heathland covers approximately 30% of Iceland, with heath vegetation being the area’s most important vegetation type. Prostrate and erect dwarf shrub and shrub species are the primary sources of dendrochronological information on the changes and characteristics of Iceland’s climate. Here, we investigate the dendrochronological potential of seven common Icelandic heathland species (Dryas octopetala, Calluna vulgaris, Salix arctica, Salix herbacea, Empetrum nigrum, Juniperus communis nana, and Betula nana) and explore the impact of climate conditions on their growth, particularly with regard to extreme meteorological events. We conducted comparative analyses among species and observed their climatic responses in a climatically, morphologically, and geologically homogeneous setting in north-eastern Iceland. After sampling, measurements, and cross-dating, we constructed local chronologies for the seven species. Of approximately 200 samples, only 113 were included in the final shrub chronologies. All chronologies covered at least 50 years, with few of them exceeding 100 years. Dendroclimatological analysis indicated that above-average temperatures in June and summer positively influence the growth of D. octopetala (June–September), J. communis (July–August), B. nana (July–August), C. vulgaris (June–August), and S. arctica (August–September). The opposite is observed for S. herbacea and E. nigrum. Climate–growth correlations indicate that the growth of these species is negatively correlated with temperature and positively correlated with winter and summer precipitation. Furthermore, among the long-lived woody species growing in Iceland, seven common species were used to assess the impact of extreme meteorological conditions on their growth. The most pronounced extreme year in the wood anatomy of Icelandic shrubs was 1979, depicted as very narrow or missing rings and as the blue ring in J. communis.

Increasing radial growth in old-growth high-elevation conifers in Southern California, USA, during the exceptional "hot drought" of 2000-2020.

Hot droughts, droughts attributed to below-average precipitation and exceptional warmth, are increasingly common in the twenty-first century, yet little is known about their effect on coniferous tree growth because of their historical rarity. In much of the American West, including California, radial tree growth is principally driven by precipitation, and narrow ring widths are typically associated with either drier or drought conditions. However, for species growing at high elevations (e.g., Larix lyalli, Pinus albicaulis), growth can be closely aligned with above-average temperatures with maximum growth coinciding with meteorological drought, suggesting that the growth effects of drought span from adverse to beneficial depending on location. Here, we compare radial growth responses of three high-elevation old-growth pines (Pinus jeffreyi, P. lambertiana, and P. contorta) growing in the San Jacinto Mountains, California, during a twenty-first-century hot drought (2000-2020) largely caused by exceptional warmth and a twentieth-century drought (1959-1966) principally driven by precipitation deficits. Mean radial growth during the hot drought was 12% above average while 18% below average during the mid-century drought illustrating that the consequences of environmental stress exhibit spatiotemporal variability. We conclude that the effects of hot droughts on tree growth in high-elevation forests may produce responses different than what is commonly associated with extended dry periods for much of western North America's forested lands at lower elevational ranges and likely applies to other mountainous regions (e.g., Mediterranean Europe) defined by summer-dry conditions. Thus, the climatological/biological interactions discovered in Southern California may offer clues to the unique nature of high-elevation forested ecosystems globally.

Circulation patterns associated with trends in summer temperature variability patterns in North America

This study improves the understanding of circulation patterns associated with regional temperature trends by characterizing boreal summer temperature variability patterns in North America using rotated S-mode principal component analysis. We analyzed gridded observational 2-m temperature datasets and the ERA5 reanalysis temperature dataset to examine the climate patterns associated with long-term trends and inter-annual variability of temperature variability patterns in North America. Our analysis revealed significant trends among some classified temperature variability patterns from 1979 to 2022 summers, with inter-annual amplitudes (i.e., a departure from the mean state) signaling toward the warm regime. The anticyclonic circulation anomaly over the temperature coherent regions associated with Greenland/northeastern Canada, and Alaska, respectively, is linked to an increase in warm air advection and above-average temperatures, while cyclonic circulation over the northeast Pacific coast enhanced warm air advection and temperature increases in the coherent region comprising the northwestern portion of North America. The increase in global mean land and ocean temperatures is strongly associated with the long-term increase in the amplitude of atmospheric circulations associated with warm regimes in parts of North America. At the interannual time scale, temperature increase over Greenland/northeastern Canada is strongly associated with the negative phase of the Arctic Oscillation. These findings highlight the modulating effects of global temperature increase and warming of the western tropical Pacific Ocean on the increasing amplitude of circulations associated with warm regimes in North America. Our results further indicate that the enhancement of anticyclonic circulations over the Arctic contributes to nearly 68% of the observed reduction in sea ice extent.

Radial Increment of Beech (Fagus sylvatica L.) Is under a Strong Impact of Climate in the Continental Biogeographical Region of Croatia.

European beech (Fagus sylvatica L.) is an important component of forests in the alpine and continental biogeographical regions of Croatia. This study aimed to (1) analyze the long-term response of beech to climate, (2) identify potentially critical climatic conditions that could negatively affect the radial increment (RI) and vitality of beech, and (3) evaluate differences in the response of beech between the two biogeographical regions in Croatia. We used the 16 × 16 km Croatian ICP Forests Level 1 network. On a total of 25 plots, we cored between 5 and 24 trees for dendrochronological analysis. Tree-ring widths (TRW) were measured and standardized using cubic spline. TRW chronologies for the two regions were calculated and correlated to the temperature and precipitation data and Standardized Precipitation and Evapotranspiration Index (SPEI) using bootstrapped correlations. Continental region precipitation from April to August and alpine region precipitation from June to August were significantly important for RI. Temperature was less important for RI than precipitation in both regions, but the importance of the negative impact of above-average temperatures in the continental region and the positive impact of above-average precipitation in the alpine region has increased over the last two decades. A comparison with the 3-month SPEI confirmed the significant influence of high temperatures and the lack of precipitation in August on the RI of beech trees in both regions.

Coral Gardens Reef, Belize: An Acropora spp. refugium under threat in a warming world.

Live coral cover has declined precipitously on Caribbean reefs in recent decades. Acropora cervicornis coral has been particularly decimated, and few Western Atlantic Acropora spp. refugia remain. Coral Gardens, Belize, was identified in 2020 as a long-term refugium for this species. This study assesses changes in live A. cervicornis coral abundance over time at Coral Gardens to monitor the stability of A. cervicornis corals, and to explore potential threats to this important refugium. Live coral cover was documented annually from 2012-2019 along five permanent transects. In situ sea-surface temperature data were collected at Coral Gardens throughout the study period and compared with calibrated satellite data to calculate Maximum Monthly Mean (MMM) temperatures and Degree Heating Weeks (DHW). Data on bathymetry, sediment, substrate, herbivore abundance, and macroalgal abundance were collected in 2014 and 2019 to assess potential threats to Coral Gardens. Live coral cover declined at all five transect sites over the study period. The greatest loss of live coral occurred between 2016 and 2017, coincident with the earliest and highest maximum average temperatures recorded at the study site, and the passage of a hurricane in 2016. Structural storm damage was not observed at Coral Gardens, though live coral cover declined after the passage of the storm. Uranium-thorium (230Th) dating of 26 dead in situ fragments of A. cervicornis collected in 2015 from Coral Gardens revealed no correlation between coral mortality and tropical storms and hurricanes in the recent past. Our data suggest that several other common drivers for coral decline (i.e. herbivory, predation, sedimentation, pH) may likely be ruled out for Coral Gardens. At the end of the study period, Coral Gardens satisfied most criteria for refugium status. However, the early onset, higher mean, and longer duration of above-average temperatures, as well as intermittent temperature anomalies likely played a critical role in the stability of this refugium. We suggest that temperature stress in 2016 and perhaps 2015 may have increased coral tissue vulnerability at Coral Gardens to a passing hurricane, threatening the status of this unique refugium.

Tree resistance to drought and bark beetle-associated mortality following thinning and prescribed fire treatments

Long-term trends show increased tree mortality over the last several decades, coinciding with above-average temperatures, high climatic water deficits, and bark beetle outbreaks. California’s recent unprecedented drought (2012–2016) highlights the need to evaluate whether thinning and prescribed fire can improve individual tree drought resistance and reduce bark beetle-associated mortality. Using a thinning and prescribed fire study on the Stanislaus-Tuolumne Experimental Forest in the central Sierra Nevada implemented prior to the drought (2011–2013), we used dendrochronological methods to estimate metrics of tree vigor (i.e., growth and resin ducts) of sugar pine (Pinus lambertiana Douglas) and white fir (Abies lowiana [Gordon & Glend.] A. Murray bis) among treatments, as well as between trees that died from bark beetle-associated mortality and their paired counterparts that survived. We used tree vigor to estimate drought resistance as the ratio between growth during drought (2012–2016) and pre-drought (2007–2011) for both species. For sugar pine, we also created analogous ratios for multiple resin duct characteristics to evaluate defense during drought. Our findings indicate that lower competition increased growth resistance of white fir, while prescribed fire had negligible impacts on growth. This translated to lower mortality, with live white fir showing higher growth resistance than those that died. While competition did not strongly affect sugar pine growth, greater growth resistance was noted for trees that lived than trees that died. However, reduced competition and prescribed fire increased defense resistance and resin duct density and relative resin duct area were negatively associated with sugar pine mortality. Live sugar pine showed greater defense resistance than dead counterparts particularly under higher levels of competition. These findings suggest thinning can promote or maintain growth during severe drought conditions and prescribed fire can be applied with negligible costs to tree growth while also producing the additional benefit of stimulating defense systems in sugar pine, which may enable them to better survive bark beetle outbreaks. Therefore, susceptibility to bark beetle-associated mortality may be ameliorated through increasing tree vigor with a combination of forest thinning and prescribed fire.

Prediction and projection of heatwaves

Heatwaves constitute a major threat to human health and ecosystems. Projected increases in heatwave frequency and severity thus lead to the need for prediction to enhance preparedness and minimize adverse impacts. In this Review, we document current capabilities for heatwave prediction at daily to decadal timescales and outline projected changes under anthropogenic warming. Various local and remote drivers and feedbacks influence heatwave development. On daily timescales, extratropical atmospheric blocking and global land–atmosphere coupling are most pertinent, and on subseasonal to seasonal timescales, soil moisture and ocean surface anomalies contribute. Knowledge of these drivers allows heatwaves to be skilfully predicted at daily to weekly lead times. Predictions are challenging beyond timescales of a few weeks, but tendencies for above-average temperatures can be estimated. Further into the future, heatwaves are anticipated to become more frequent, persistent and intense in nearly all inhabited regions, with trends amplified by soil drying in some areas, especially the mid-latitudes. There is also an increased occurrence of humid heatwaves, especially in southern Asia. A better understanding of the relevant drivers and their model representation, including atmospheric dynamics, atmospheric and soil moisture, and surface cover should be prioritized to improve heatwave prediction and projection.

Der Fremdling im Therapiegarten – Cis chinensis (Coleoptera, Ciidae) und sein Umfeld

Samples of the tree fungus Antrodia xantha were collected on Pinus strobus in the therapy garden of the UPK campus (University Psychiatric Clinics) in Basel in summer 2021. The samples contained an alien Ciidae species new to Switzerland: Cis chinensis Lawrence, 1991, a species otherwise mainly known as a storage pest of commercially dried fungi. The adults and larvae of the Basel population are described and illustrated. When comparing the size of the adults of the two sample series collected two weeks apart, statistically significant differences were found. It appears that the above-average temperatures in June 2021 favoured the size of the second group. A number of (4–)5 larval stages are postulated for larval development. As an endoparasitoid of the eggs of C. chinensis, an unknown Mymaridae of the genus Cleruchus was found. Noteworthy was an unusually heavy infestation of Ciidae by phoretic mites (Histiostomatidae). During follow-up surveys in early 2022, additional individuals of C. chinensis were also found on the fruitbodies of other fungi growing in the immediate vicinity of the site where the population of the species was initially observed on A. xantha. A list of all Ciidae detected on the UPK campus is provided, and the spectrum of host-fungi of C. chinensis is discussed.

The Influence of Intraseasonal Oscillations on Humid Heat in the Persian Gulf and South Asia

Abstract Humans’ essential ability to combat heat stress through sweat-based evaporative cooling is modulated by ambient air temperature and humidity, making humid heat a critical factor for human health. In this study, we relate the occurrence of extreme humid heat in two focus regions to two related modes of intraseasonal climate variability: the Madden–Julian oscillation (MJO) and the boreal summer intraseasonal oscillation (BSISO). In the Persian Gulf and South Asia during the May–June and July–August seasons, wet-bulb temperatures of 28°C are found to be almost twice as likely during certain oscillation phases than in others. Variations in moisture are found, to varying degrees, to be an important ingredient in anomalously high wet-bulb temperatures in all three areas studied, influenced by distinct local circulation anomalies. In the Persian Gulf, weakening of climatological winds associated with the intraseasonal oscillation’s propagating center of convection allows for anomalous onshore advection of humid air. Anomalously high wet-bulb temperatures in the northwestern region of South Asia are closely aligned with positive specific humidity anomalies associated with the convectively active phase of the oscillation. On the southeastern coast of India, high wet-bulb temperatures are associated with convectively inactive phases of the intraseasonal oscillation, suggesting that they may be driven by increased surface insolation and reduced evaporative cooling during monsoon breaks. Our results aid in building a foundation for subseasonal predictions of extreme humid heat in regions where it is highly impactful. Significance Statement Understanding when and why extreme humid heat occurs is essential for informing public health efforts protecting against heat stress. This analysis works to improve our understanding of humid heat variability in two at-risk regions, the Persian Gulf and South Asia. By exploring how subseasonal oscillations affect daily extreme events, this analysis helps bridge the prediction gap between weather and climate. We find that extreme humid heat is more than twice as likely during specific phases of these oscillations than in others. Extremes depend to different extents upon combinations of above-average temperature and humidity. This new knowledge of the regional drivers of humid heat variability is important to better prepare for the increasingly widespread health and socioeconomic impacts of heat stress.

Effects of Climate on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) Growth Southeast of the European Alps.

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is a non-native tree species in Slovenia with the potential to partially replace Norway spruce in our native forests. Compared to spruce, it has several advantages in terms of volume growth, wood quality and tolerance to drought. This is important given the changing climate in which spruce is confronted with serious problems caused by increasing temperatures and drought stress. At three sites (one on non-carbonate bedrock and deep soils, and two on limestone with soil layers of varying depths), 20 Douglas-fir and 20 spruce per site were sampled in order to compare their radial growth response to climate and drought events. The radial growth of Douglas-fir exceeds that of spruce by about 20% on comparable sites. It is more responsive to climate than spruce. Above-average temperatures in February and March have a significant positive effect on the radial growth of Douglas-fir. In recent decades, above-average summer precipitation has also had a positive influence on the radial growth of Douglas-fir. Compared to spruce, Douglas-fir is less sensitive to extreme drought events. Our results indicate that Douglas-fir may be a good substitute for spruce in semi-natural managed forest stands in Slovenia. The planting of Douglas-fir should be allowed in Slovenian forests, but the proportion of it in forest stands should be kept lower than is the case with spruce today.

Boom and bust cycles of black-tailed prairie dog populations in the Thunder Basin grassland ecosystem

AbstractBlack-tailed prairie dogs (Cynomys ludovicianus) exhibit boom and bust cycles in landscapes where they are affected by outbreaks of plague caused by the introduced bacterium Yersinia pestis. We examined spatiotemporal dynamics of black-tailed prairie dog colonies in the Thunder Basin National Grassland, Wyoming over a period of 21 years. The colony complex experienced three plague epizootics during that time, and consequently three boom and bust cycles. The entire prairie dog colony complex collapsed over a 1-year period during the first and third epizootics, and over a 3-year period during the second epizootic. The boom and bust cycles were characterized by relatively rapid contractions in total area occupied by prairie dogs during a plague outbreak (e.g., >99% decline from 10,604 ha to 47 ha over 1 year [2017–2018]) followed by much slower recovery times (e.g., an increase from 410 ha to 10,604 ha over 11 years [2006–2017]). Prairie dogs occupied a total of 10,604 ha during at least one survey within the study period, but much of the area was not continuously occupied over time. We found that each of the three plague outbreaks occurred in years with highly connected prairie dog colonies and slightly above-average temperatures and summer precipitation, which were preceded by a dry year. Although plague outbreaks were associated with climatic conditions, we were unable to detect a role of climate in driving colony expansion. Our results illustrate the cyclic and extreme nature of fluctuations in black-tailed prairie dog colony size and distribution in a landscape where plague occurs and illuminate some of the drivers of these cycles. Further, our work shows how introduced diseases can dramatically influence populations of a keystone species, with important consequences for the broader ecological system.

Identification, characteristics and dynamics of Arctic extreme seasons

Abstract. The Arctic atmosphere is strongly affected by anthropogenic warming leading to long-term trends in surface temperature and sea ice extent. In addition, it exhibits strong variability on timescales from days to seasons. While recent research elucidated processes leading to short-term extreme conditions in the Arctic, this study investigates unusual atmospheric conditions on the seasonal timescale. Based on a principal component analysis in the phase space spanned by the seasonal-mean values of surface temperature, precipitation and the atmospheric components of the surface energy balance, individual seasons are objectively identified that deviate strongly from a running-mean climatology and that we define as extreme seasons. Given the strongly varying surface conditions in the Arctic, this analysis is done separately in Arctic sub-regions that are climatologically characterized by either sea ice, open ocean or mixed conditions. Using ERA5 reanalyses for the years 1979–2018, our approach identifies two to three extreme seasons for each of winter, spring, summer and autumn, with strongly differing characteristics and affecting different Arctic sub-regions. Two extreme winters affecting the Kara and Barents seas are selected for a detailed investigation of their substructure, the role of synoptic-scale weather systems, and potential preconditioning by anomalous sea ice extent and/or sea surface temperature at the beginning of the season. Winter 2011/12 started with average sea ice coverage and was characterized by constantly above-average temperatures during the season related mainly to frequent warm air advection by quasi-stationary cyclones in the Nordic Seas. In contrast, winter 2016/17 started with reduced sea ice and enhanced sea surface temperatures in the Kara and Barents seas, which, together with increased frequencies of cold air outbreaks and cyclones, led to large upward surface heat flux anomalies and strongly increased precipitation during this extreme season. In summary, this study shows that extreme seasonal conditions in the Arctic are spatially heterogeneous, related to different near-surface parameters and caused by different synoptic-scale weather systems, potentially in combination with surface preconditioning due to anomalous ocean and sea ice conditions at the beginning of the season. The framework developed in this study and the insight gained from analyzing the ERA5 period will be beneficial for addressing the effects of global warming on Arctic extreme seasons.

Ambiente e Salute News - n.14 marzo-aprile 2022

Environment and health As we write, a winter with little rainfall and spring with above-average temperatures have just ended. We are experiencing climate change and have to manage and mitigate the effect of the scarcity of water resources. This does not only affect farmers or growers and ranchers but all of us because the water shortage translates into a reduction in crops. The dissociation between public health policies and climate action, which results in millions of avoidable adverse outcomes and deaths every year is worrying. But maybe something is moving: the Ministry's Ecological Transition Plan proposal published in August 2021 for the first time reports the health benefits of climate action and calls for a health approach in all policies. The importance of soil remediation from toxic substances still highlights the difficulty and complexity of the problem, but also the importance for human health of adequate remediation and control systems. The presence of green spaces in schools and urban areas is confirmed as a winning choice for the children’s health as the indications not using electronic devices in the first 1000 days. This issue summarizes the main articles published in the monitored journals, which allows us to deepen these issues. All articles and editorials deemed worthy of attention are listed divided by topic, with a concise comment. This number is based on the systematic review of the March and April 2022 publications.

Alaskan Seabird Die-Offs

Prior to 2015, seabird die-offs in Alaskan waters (Northern Gulf of Alaska, eastern Bering Sea, eastern Chukchi Sea) were rare, typically occurred in mid-winter, and were linked to epizootic disease events (Bodenstein et al., 2015) or above-average ocean temperatures associated with strong El Nino-Southern Oscillation events. An exception was late summer of 1997, a year with unusually warm waters in the southeastern Bering Sea, when possibly as many as 10% of the several million short-tailed shearwaters (Ardenna tenuitortris) present in the area died of starvation because their principal prey, euphausiids, were scarce or hard to find in a widespread coccolithophore bloom (Baduini et al., 2001). Since 2015, such mass mortality events have been annual occurrences. In 2015, between 470,000 and 1.03 million common murres (Uria aalge) were estimated to have died in the Gulf of Alaska due to anomalous ocean conditions and the impacts on forage fish associated with the 2014–2016 Pacific marine heatwave (Piatt et al., 2020; Arimitsu et al., 2021). Another large die-off event occurred during late summer of 2019 (Figure 1), when over 10,000 carcasses of short-tailed shearwaters washed onto beaches of Bristol Bay and the Alaska Peninsula in the southeastern Bering Sea. Total mortality during that summer was likely much greater than reported given the region’s expansive coastline and sparse human population.

Can Native Plants Mitigate Climate-related Forage Dearth for Honey Bees (Hymenoptera: Apidae)?

Extreme weather events, like high temperatures and droughts, are predicted to become common with climate change, and may negatively impact plant growth. How honey bees (Apis mellifera L. [Hymenoptera: Apidae]) will respond to this challenge is unclear, especially when collecting pollen, their primary source of protein, lipids, and micro-nutrients. We explored this response with a data set from multiple research projects that measured pollen collected by honey bees during 2015–2017 in which above-average temperatures and a drought occurred in 2017. We summarized the abundance and diversity of pollen collected from July to September in replicated apiaries kept at commercial soybean and corn farms in Iowa, in the Midwestern USA. The most commonly collected pollen was from clover (Trifolium spp. [Fabales: Fabaceae]), which dramatically declined in absolute and relative abundance in July 2017 during a period of high temperatures and drought. Due to an apparent lack of clover, honey bees switched to the more drought-tolerant native species (e.g., Chamaecrista fasciculata [Michx.] Greene [Fabales: Fabaceae], Dalea purpurea Vent. [Fabales: Fabaceae], Solidago spp. [Asterales: Asteraceae]), and several species of Asteraceae. This was especially noticeable in August 2017 when C. fasciculata dominated (87%) and clover disappeared from bee-collected pollen. We discuss the potential implications of climate-induced forage dearth on honey bee nutritional health. We also compare these results to a growing body of literature on the use of native, perennial flowering plants found in Midwestern prairies for the conservation of beneficial insects. We discuss the potential for drought resistant-native plants to potentially promote resilience to climate change for the non-native, managed honey bee colonies in the United States.

Associations between Weather, Air Quality and Moderate Extreme Cancer-Related Mortality Events in Augsburg, Southern Germany.

While many authors have described the adverse health effects of poor air quality and meteorological extremes, there remain inconsistencies on a regional scale as well as uncertainty about the single and joint effects of atmospheric predictors. In this context, we investigated the short-term impacts of weather and air quality on moderate extreme cancer-related mortality events for the urban area of Augsburg, Southern Germany, during the period 2000–2017. First, single effects were uncovered by applying a case-crossover routine. The overall impact was assessed by performing a Mann–Whitney U testing scheme. We then compared the results of this procedure to extreme noncancer-related mortality events. In a second step, we found periods with contemporaneous significant predictors and carried out an in-depth analysis of these joint-effect periods. We were interested in the atmospheric processes leading to the emergence of significant conditions. Hence, we applied the Principal Component Analysis to large-scale synoptic conditions during these periods. The results demonstrate a strong linkage between high-mortality events in cancer patients and significantly above-average levels of nitrogen dioxide (NO2) and particulate matter (PM2.5) during the late winter through spring period. These were mainly linked to northerly to easterly weak airflow under stable, high-pressure conditions. Especially in winter and spring, this can result in low temperatures and a ground-level increase and the accumulation of air pollution from heating and traffic as well as eastern lateral advection of polluted air. Additionally, above-average temperatures were shown to occur on the days before mortality events from mid-summer through fall, which was also caused by high-pressure conditions with weak wind flow and intense solar radiation. Our approach can be used to analyse medical data with epidemiological as well as climatological methods while providing a more vivid representation of the underlying atmospheric processes.

Spatio-temporal variations in stable isotopes in peri-urban catchments: A preliminary assessment of potential and challenges in assessing streamflow sources

In peri-urban catchments where treated wastewater effluents are released into surface waters, knowledge of water sources and partitioning is important for mitigating water quality impacts, particularly during warm and dry periods with low discharge rates. Useful tools for the identification of water sources and flow paths under different wetness conditions are isotope tracers. However, very few studies have been carried out so far in urbanized catchments with complex land use distributions where natural headwaters interact with engineered components, e.g. effluent discharge. We undertook spatio-temporal sampling of isotopes, combined with water quality measurements, to complement climatic and hydrometric data across the 220 km2 peri-urban Erpe catchment near Berlin and assess seasonal changes in water sources during two exceptionally warm and dry years (2018 and 2019). The study showed a deterioration of water quality downstream of two municipal wastewater treatment plants; and the depletion of groundwater storage, along with isotopic enrichment of the stream, in summer 2019 (the second consecutive year with above-average temperatures and marked precipitation deficits). Streamflow in the upper reaches of the catchment was dominated by groundwater-fed tributaries in winter, but became increasingly dominated by wastewater in summer. In the lower catchment, flows were dominated by effluent from a large wastewater treatment plant, especially in summer. Young water from precipitation and urban storm runoff accounted for < 10 % of streamflow, despite the catchment being ~ 20 % urban. Similarities in the composition of wastewater and other runoff sources resulted in high uncertainties in end member separation and highlight the need for monitoring of other tracers to better characterize water impacts. Given climate change projections for the region are for drier, warmer summers, wastewater is likely to become a more dominant component of streams, which may have implications for environmental quality and ecosystem services.

Examining the sensitivity of the terrestrial carbon cycle to the expression of El Niño

Abstract. The El Niño‐-Southern Oscillation (ENSO) influences the global climate and the variability in the terrestrial carbon cycle on interannual timescales. Two different expressions of El Niño have recently been identified: (i) central Pacific (CP) and (ii) eastern Pacific (EP). Both types of El Niño are characterised by above-average sea surface temperature anomalies at the respective locations. Studies exploring the impact of these expressions of El Niño on the carbon cycle have identified changes in the amplitude of the concentration of interannual atmospheric carbon dioxide (CO2) variability following increased tropical near-surface air temperature and decreased precipitation. We employ the dynamic global vegetation model LPJ-GUESS (Lund–Potsdam–Jena General Ecosystem Simulator) within a synthetic experimental framework to examine the sensitivity and potential long-term impacts of these two expressions of El Niño on the terrestrial carbon cycle. We manipulated the occurrence of CP and EP events in two climate reanalysis datasets during the latter half of the 20th and early 21st century by replacing all EP with CP and separately all CP with EP El Niño events. We found that the different expressions of El Niño affect interannual variability in the terrestrial carbon cycle. However, the effect on longer timescales was small for both climate reanalysis datasets. We conclude that capturing any future trends in the relative frequency of CP and EP El Niño events may not be critical for robust simulations of the terrestrial carbon cycle.

Risk of short-term biodiversity loss under more persistent precipitation regimes.

Recent findings indicate that atmospheric warming increases the persistence of weather patterns in the mid-latitudes, resulting in sequences of longer dry and wet periods compared to historic averages. The alternation of progressively longer dry and wet extremes could increasingly select for species with a broad environmental tolerance. As a consequence, biodiversity may decline. Here we explore the relationship between the persistence of summer precipitation regimes and plant diversity by subjecting experimental grassland mesocosms to a gradient of dry-wet alternation frequencies whilst keeping the total precipitation constant. The gradient varied the duration of consecutive wet and dry periods, from 1 up to 60days with or without precipitation, over a total of 120days. An alternation of longer dry and wet spells led to a severe loss of species richness (up to -75% relative to the current rainfall pattern in W-Europe) and functional diversity (enhanced dominance of grasses relative to nitrogen (N)-fixers and non-N-fixing forbs). Loss of N-fixers and non-N-fixing forbs in severe treatments was linked to lower baseline competitive success and higher physiological sensitivity to changes in soil moisture compared to grasses. The extent of diversity losses also strongly depended on the timing of the dry and wet periods. Regimes in which long droughts (≥20days) coincided with above-average temperatures showed significantly more physiological plant stress over the experimental period, greater plant mortality, and impoverished communities by the end of the season. Across all regimes, the duration of the longest period below permanent wilting point was an accurate predictor of mortality across the communities, indicating that increasingly persistent precipitation regimes may reduce opportunities for drought stress alleviation. We conclude that without recruitment, which was precluded in this experiment, summer precipitation regimes with longer dry and wet spells will likely diminish plant diversity, at least in the short term.