Recent Climatic Conditions Research Articles

Spatiotemporal changes in the community and demography of mesozooplankton in the eastern Indian sector of the Southern Ocean during austral summer 2018/2019

The Southern Ocean is facing rapid environmental changes. However, few studies have been conducted on the spatiotemporal variability of mesozooplankton communities under recent climatic conditions, particularly in the eastern Indian sector. This study describes the spatiotemporal variability of the mesozooplankton community and the demographics of large copepods and krill in this sector, sampled through a Rectangular Mid-Water Trawl with 1 m2 mouth area (RMT1) during the austral summer of 2018/2019 as part of the KY1804 survey. Cluster analysis indicated that the mesozooplankton community was divided into five groups that showed only small longitudinal differences, as they were affected by oceanic fronts. Part of the variability was explained by physical (local upwelling) and biological features (e.g., the occurrence of species showing a specific spatial distribution, such as Euphausia crystallorophias). Horizontal changes in the zooplankton community structure were not attributed to temporal changes during the 2-month sampling period. The demographics of the dominant species, Calanoides acutus, Calanus propinquus, Metridia gerlacheri, and Thysanoessa macrura, exhibited significant temporal differences in abundance or mean stage index (MSI) between the early and late seasons. These differences matched the growth rates estimated in previous studies, suggesting that their growth during the study period was constant without regional differences. There were no evident changes in the abundance or demographics of Rhinalanus gigas, suggesting that they were in their reproductive season. These species-specific demographics could be explained by the species life cycles: growth in C. acutus and C. propinquus and reproduction in R. gigas during the austral summer. Abundances and MSIs confirmed the growth of dominant copepods and krill during the sampling period; however, no evident seasonal changes were observed in the zooplankton community structure. The findings of this study contribute to the understanding of lower trophic levels in marine ecosystems and the present carbon cycle in the eastern Indian sector of the Southern Ocean.

An integrated framework for rainfall prediction and analysis using a Stacked Heterogeneous Ensemble Model (SHEM)

Recent climate conditions in India have led to numerous disasters, including floods, overflowing rivers, broken dams, and reduced vegetation. Machine learning aims to train models to make predictions based on historical data. Although many studies have focused on predictions and model building, this research introduces a novel integrated framework using a Stacked Heterogeneous Ensemble Model (SHEM). It aims to enhance prediction accuracy by employing another novel approach for imputing missing values, the Variable Specific Hot Deck (VSHD) imputation method. The outcomes were contrasted with established machine learning techniques, including random forest, decision tree, k-nearest neighbor, and support vector machine. After completing the imputation, we proceeded to implement the SHEM model. Real-time climate data for the Cuddalore location in Tamil Nadu state, South India was collected from the NASA Power Access viewer portal to verify the accuracy level of the proposed model. Performance analysis indicates that the proposed imputation outperforms all four alternative models with a 30% average improvement in accuracy. Moreover, the developed SHEM model has a reduced RMSE value of 0.321 and an R-squared value of 0.952 and shows a 9% improvement in accuracy compared to the base model’s performance. Furthermore, these prediction results are compared to an LSTM (Long Short Term Memory), a deep learning model to calculate accuracy and loss, showing that the proposed achieves high accuracy and significant loss during validation. The obtained results can serve as a guideline for atmospheric scientists and various weather forecasting applications, helping them to choose the most appropriate machine learning method for their prediction task.

Ensemble hindcasting of winds and waves for the coastal and oceanic region of Southern Brazil

When hindcasting wave fields of storm events with wave models, the quality of the results strongly depends on several factors such as the computational grid resolution and the accuracy of the atmospheric forcing. In an effort to minimize the uncertainties involved in this process, three ocean wave and surface wind ensemble hindcast systems were established using the Simulating WAves Nearshore (SWAN) model and Weather Research and Forecasting Model (WRF) with atmospheric data from ERA5 Ensemble of Data Assimilation (EDA) as well as deterministic high-resolution systems. We established three ensemble systems to tackle this: SWN-ERA5EDA using ERA5-EDA global reanalyses winds, SWN-WRFERA5 employing WRF downscaling of ERA5-EDA, and SWN-WRFPPar incorporating WRF multi-physics runs for dynamical downscaling. This study focuses on extreme events in southern Brazil during an austral winter, highlighting the importance of increasing the resolution of ocean wave and surface wind data to provide more accurate and reliable forecasts for coastal and marine activities. Our analyses revealed that atmospheric downscaling performed with WRF not only increased the ensemble spread by significant amounts but also enhanced the sharpness of the wave ensemble hindcast compared with those based solely on the ERA5 EDA. Specifically, for the Rio Grande buoy location, the significant wave height (Hs) from the SWN-WRFERA5 system showed an increase of 0.5 over SWN-ERA5, and Hs from the SWN-WRFPPar system increased by 0.6. Additionally, the wave peak period (Tp) for both SWN-WRFERA5 and SWN-WRFPPar systems experienced an increase of 1.2 compared to SWN-ERA5. Additionally, the ensemble produced with the WRF multi-physics approach captured peaks in the significant wave height registered by the buoy that were not reproduced by other ensemble systems, demonstrating an improvement in predictive accuracy, despite presenting a smaller correlation between spread and strong localized wave variations. Besides quantifying the hindcast error, the methodology presented in this work also offers a way to generate alternative and improved representations of past extreme events. This approach significantly contributes to our ability to sample recent climatic conditions and expand the dataset for statistical analyses, which is especially valuable for ocean and coastal engineering projects. This study underscores the critical role of enhancing computational and methodological approaches in wave modeling for better understanding and mitigating the impacts of extreme weather events on coastal and oceanic regions.

Divinizing Nature for Sustainable Global Growth: The Indian Perspective

The recent catastrophic climate conditions and the spate of wildfires, floods, cyclones, etc. on an unparalleled scale sweeping most parts of the globe has sent mankind in a tizzy. Despite numerous summits and conferences of world leaders and the action plans continue to make headlines even though the real effect on the ground seems suspect. Faultlines flagged include the seemingly unsustainable global market economy, high-level consumerism, widespread deforestation, emissions from ever-burgeoning number of automobiles and fossil-fuel fed industries, use of chemicals, building of big dams, etc. While all this is true, the real change has to come about in human attitude to nature. From the urge to exploit nature, it has to be of an interdependence based on respect for the natural elements and creatures because these maintain balance and provide congenial environment for life. My paper analyses the situation and concludes that for this to happen, we need to involve heart and soul as much as the mind. Our native cultures existing since ages and finding expression in ancient as also contemporary literatures provide an answer to tackle the fearsome scenario facing us, and this is to treat nature not just as a living being, but rather a divine being.

Reconstructed and projected beach temperatures reveal where flatback turtles are most at risk from climate change

Nest temperature is the predominant driver of emergence success and primary sex ratios in sea turtles, with female offspring produced at higher temperatures due to temperature-dependent sex determination. However, emergence success and primary sex ratios are unfeasible to measure at scale, making methods to estimate these life-history traits from predicted sand temperatures highly desirable for long-term conservation planning in the context of climate change. To address this, we used a mechanistic microclimate model to predict hourly sand temperatures, over 32 nesting seasons since 1986, at 402 West Australian beaches supporting nesting by flatback turtles (Natator depressus). Predicted sand temperatures indicated that ∼70% of these beaches carried a 'very low' to 'intermediate' risk of subjecting embryos to thermal stress. By combining these temperature predictions with a physiological model, current and future emergence success and sex ratios were projected for ten different beaches spanning a range of thermal microclimates, under various climate change scenarios. Under recent climate conditions, emergence success averaged 76%, but declined to 63% and 37% with a 2°C and 4°C increase in air temperature, respectively. The sex ratios of hatchlings varied by location, but extremely skewed sex ratios were anticipated in a 4°C warming scenario. Our projections reveal that 'high risk' nesting beaches will regularly experience clutch failure as climate change progresses, while cooler beaches offer long-term nesting potential and require protection from additional anthropogenic impacts. These projections, covering an entire genetic stock, supply demographic data for assessing extinction risks and this method can be applied to sea turtle populations worldwide.

Northern Hemisphere Extratropical Cyclone Clustering in ERA5 Reanalysis and the CESM2 Large Ensemble

Abstract Extratropical cyclones are a dominant feature of the midlatitudes, and often occur as storm sequences. This phenomenon is known as cyclone clustering, which is common over regions like the eastern North Atlantic and western Europe. Here, intense clustered cyclones may lead to large cumulative socioeconomic impacts. There are several different approaches to quantify cyclone clustering, but a detailed evaluation on how clustering may change in a warmer climate is missing. We perform a cyclone clustering analysis for the Northern Hemisphere midlatitudes using the ERA5 reanalysis to characterize clustering during 1980–2020. Moreover, we use large ensemble simulations of the Community Earth System Model version 2 following the SSP3-7.0 scenario to compare clustering during 2060–2100 to 1980–2020. Our model simulations show significant enhancement in cyclone clustering over Europe for 3 and 4 cyclones within 7 days in the future decades, which is increasing by up to 25% on average during 2060–2100 compared to 1980–2020. In contrast, cyclone clustering decreases along the west coast of the United States and Canada by up to 24.3% and by 10.1% in the Gulf of Alaska for the same periods. In a warmer climate, clustered cyclones have lower minimum pressure and larger radii and depths compared to nonclustered events. Our findings suggest that change in future cyclone clustering depends on regions affected by global warming, with implications for the cumulative windstorm risk. Significance Statement Storm sequences like the one of December 1999 (Anatol, Lothar, and Martin) have led to large socioeconomic impacts in Europe. It is still unclear how such events will change under global warming. We analyze storm sequences in a reanalysis and a large climate model ensemble for recent (1980–2020) and future climate conditions (2060–2100). Our results show a significant enhancement of storm sequences over Europe for 3 and 4 storms within 7 days, while a decrease is found along the west coast of the United States, western Canada, and in the Gulf of Alaska in future decades. Our findings suggest that the characteristics of cyclone clustering may change in a warmer world, and thus also the associated impacts.

Global reductions in manual agricultural work capacity due to climate change.

Manual outdoor work is essential in many agricultural systems. Climate change will make such work more stressful in many regions due to heat exposure. The physical work capacity metric (PWC) is a physiologically based approach that estimates an individual's work capacity relative to an environment without any heat stress. We computed PWC under recent past and potential future climate conditions. Daily values were computed from five earth system models for three emission scenarios (SSP1-2.6, SSP3-7.0, and SSP5-8.5) and three time periods: 1991-2010 (recent past), 2041-2060 (mid-century) and 2081-2100 (end-century). Average daily PWC values were aggregated for the entire year, the growing season, and the warmest 90-day period of the year. Under recent past climate conditions, the growing season PWC was below 0.86 (86% of full work capacity) on half the current global cropland. With end-century/SSP5-8.5 thermal conditions this value was reduced to 0.7, with most affected crop-growing regions in Southeast and South Asia, West and Central Africa, and northern South America. Average growing season PWC could falls below 0.4 in some important food production regions such as the Indo-Gangetic plains in Pakistan and India. End-century PWC reductions were substantially greater than mid-century reductions. This paper assesses two potential adaptions-reducing direct solar radiation impacts with shade or working at night and reducing the need for hard physical labor with increased mechanization. Removing the effect of direct solar radiation impacts improved PWC values by 0.05 to 0.10 in the hottest periods and regions. Adding mechanization to increase horsepower (HP) per hectare to levels similar to those in some higher income countries would require a 22% increase in global HP availability with Sub-Saharan Africa needing the most. There may be scope for shifting to less labor-intensive crops or those with labor peaks in cooler periods or shift work to early morning.

The Loss of Ecological Control, Pastoralist Migration and Indigenous Knowledge in Tanzania

This article is based on a study on the implications of climate change in bringing about loss of ecological control and climate induced, forced pastoralist migration from one ecosystemic basin to another. It brings out a discussion that migration between different ecosystems lead to the inevitable loss of location-specific indigenous knowledge. This in turn contributes to loss of epidemic control which lead to increased livestock and human vulnerabilities in the destination areas. The article is based on empirical evidence demonstrating that pastoralists are increasingly becoming a vulnerable population group, and internally displaced to new ecosystems as a result of migration as a coping mechanism from extreme weather variations. The study was guided by three objectives: a) to determine whether such migration trends are induced by climate change and loss of ecological control; b) to determine recent trends of pastoralist and livestock migration in Tanzania, and c) to determine the implication of pastoralist migration and loss of indigenous knowledge. The article is based on a study that interviewed 544 pastoralist households in seven districts in Tanzania. A total of 54 Focus Group Discussions and 17 Key Informant Interviews were conducted to complement the household survey. The study provided evidence derived from case-study areas in which recent climatic changes and extreme weather conditions have had accelerated loss of ecological control leading to forced out- migration, depletion of location specific indigenous knowledge and increased vulnerability to epidemics. The article concludes that loss of ecological control is closely associated with loss of epidemic control.

Synthesis of high-Andean peat cores reveals suite of Holocene climate conditions favorable for peat formation

Peat-core records have a long history of being used for paleoclimate reconstructions in northern high-latitude regions but are less common in the southern tropical zone. In this study, we present a synthesis of published peat-core reconstructions and basal ages from high-elevation (>3000 m a.s.l.) sites in the northern and central Andes of South America. We complement this database by providing a new multi-proxy peat-core-based paleoecological reconstruction from the Alta Murmurani peatland, Cordillera Vilcanota, Peru. This record, with a peat inception age of 8980 cal. yr BP, was analyzed for plant macrofossils and stable isotopes (carbon, oxygen). This review (1) assesses the timing of peat initiation and development across the tropical high-elevation region of South America (8°N to 27°S); (2) assesses the reliability of peat-core paleoclimate reconstructions by comparing the peat-core inferences across sites and against other independent archives (e.g., lake sediments, ice cores, speleothems); and (3) determines which hydroclimatic conditions are favorable for peat formation and expansion across the study area. Our results show that peat initiation occurred throughout the Holocene, progressing from the northern Andes to central Andes, with highest initiation frequencies clustered at ca. 10,700 cal. yr BP and 8300 cal. yr BP, respectively. Our synthesis reveals that peat cores can be used to assess regional paleoclimate trends in the central Andes using a multi-proxy approach combining micro- and macrofossils such as pollen, stable isotopes, as well as organic and inorganic elemental analyses. We also identify three optimal peat-forming time periods, all with optimally wet conditions occurring at transitional hydroclimate phases: (1) following deglaciation, with warming temperatures and increased moisture related to glacial runoff (ca. 11,000 cal. yr BP and ∼8000 cal. yr BP), (2) under moderate moisture regimes related to intensifying ENSO and warmer conditions (∼3500 cal. yr BP), and (3) under conditions related to increased precipitation at the beginning of a cold period (Little Ice Age). We show that either regional climate (e.g., changes in precipitation) or local conditions (e.g., changes in glacial runoff) can promote peat formation across the study region.

The fingerprint of climate variability on the surface ocean cycling of iron and its isotopes

Abstract. The essential micronutrient iron (Fe) limits phytoplankton growth when dissolved Fe (dFe) concentrations are too low to meet biological demands. However, many of the processes that remove, supply, or transform Fe are poorly constrained, which limits our ability to predict how ocean productivity responds to ongoing and future changes in climate. In recent years, isotopic signatures (δ56Fe) of Fe have increasingly been used to gain insight into the ocean Fe cycle, as distinct δ56Fe endmembers of external Fe sources and δ56Fe fractionation during processes such as Fe uptake by phytoplankton can leave a characteristic imprint on dFe signatures (δ56Fediss). However, given the relative novelty of these measurements, the temporal scale of δ56Fediss observations is limited. Thus, it is unclear how the changes in ocean physics and biogeochemistry associated with ongoing or future climate change will affect δ56Fediss on interannual to decadal timescales. To explore the response of δ56Fediss to such climate variability, we conducted a suite of experiments with a global ocean model with active δ56Fe cycling under two climate scenarios. The first scenario is based on an atmospheric reanalysis and includes recent climate variability (1958–2021), whereas the second comes from a historical and high-emissions climate change simulation to 2100. We find that under recent climatic conditions (1975–2021), interannual δ56Fediss variability is highest in the tropical Pacific due to circulation and productivity changes related to the El Niño–Southern Oscillation (ENSO), which alter both endmember and uptake fractionation effects on δ56Fediss by redistributing dFe from different external sources and shifting nutrient limitation patterns. While the tropical Pacific will remain a hotspot of δ56Fediss variability in the future, the most substantial end-of-century δ56Fediss changes will occur in the Southern Hemisphere at middle to high latitudes. These arise from uptake fractionation effects due to shifts in nutrient limitation. Based on these strong responses to climate variability, ongoing measurements of δ56Fediss may help diagnose changes in external Fe supply and ocean nutrient limitation.

Niche evolution and diversification in Middle Eastern stream salamanders (Paradactylodon): vulnerability to future climate change

Abstract The relict genus Paradactylodon is narrowly distributed in temperate forests throughout the Middle East region, including P. mustersi in Afghanistan, P. persicus, and P. gorganensis in northwestern and northeastern Iran. Recent phylogenetic analyses suggest that the Iranian Paradactylodon populations may belong to a single species, P. persicus. In this study, we addressed how climatic niche conservatism and/or niche divergence may have affected the evolution of all Paradactylodon species using ecological niche models and multivariate niche analyses to identify niche overlap and assess equivalency and similarity tests. We also used an ensemble of ten algorithms to predict Paradactylodon species distributions for recent (1970-2000) and future (2081-2100) climate conditions. The results show that future climate change may cause the loss of 80 to 97% of these species’ suitable habitat, especially at lower elevations. The niche divergence hypothesis was supported by the results of niche equivalency tests on P. persicus vs. P. gorganensis (and vice versa) with moderate overlap (D = 0.23, I = 0.41) and P. persicus vs. P. mustersi (and vice versa) with little overlap (D = 0.05, I = 0.06). Meanwhile, the niche similarity test for the niche conservatism hypothesis revealed significant results for P. persicus vs. P. gorganensis, P. mustersi vs. P. persicus, and P. persicus + P. gorganensis (as a single species) vs. P. mustersi. Due to these complex evolutionary ecological patterns and allopatric distributions, we recommend that P. gorganensis be considered a valid subspecies.

Evolution of the dynamics of Airdrop Glacier, western Axel Heiberg Island, over a seven-decade-long advance

Various remotely sensed data, including historical aerial photographs, declassified intelligence satellite photographs, optical satellite imagery, and synthetic aperture radar data, were used to undertake the first comprehensive reconstruction of the dynamics of Airdrop Glacier on Axel Heiberg Island, Nunavut. Observations show a continuous terminus advance totalling ∼6 km since 1950 and notably less variability in its surface velocities in comparison to adjacent Iceberg Glacier. This advance is concurrent with relatively high flow rates over its entire surface, resulting in significant thickening near the terminus and thinning at higher elevations. Velocities have more than halved from the mid-2000s to 2021, but without any definitive evidence of previous flow instabilities, we cannot confirm whether Airdrop's behaviour is cyclic in nature and therefore characteristic of a surge. Instead, Airdrop Glacier could be experiencing a delayed response to the positive mass balance conditions of the Little Ice Age, which could also explain the advance of other nearby glaciers. Its recent slowdown could then be indicative of a gradual adjustment to recent climatic conditions. This study highlights the need for comprehensive studies of glacier dynamics in the Canadian Arctic to improve our understanding of the factors triggering dynamic instabilities and causing the observed variety of behaviours.

Predicting potential range shifts using climatic time series and niche models: A Neotropical montane shrew's case

Ecological niche models (ENMs) can forecast species' potential range shifts by transferring a model to a future climatic scenario. However, this approximation does not identify whether range shifts have occurred in species' distributional limits in the last several decades. Given ongoing anthropogenic climate change, changes in distributional limits are expected to occur (poleward and upslope for several montane species). Here, I use a climatic time series to predict potential changes in distributional limits in response to climate change over the last four decades, using the Mexican small-eared shrew (Cryptotis mexicanus), a montane cloud-forest species, as an example. I transferred the ENM (tuned to optimize complexity) to a series of thirty-year bioclimatic periods between 1979 and 2019 created with monthly precipitation and temperature data. I detected trends in suitability and bioclimatic variables using a Mann-Kendall test and identified which variables could be driving the suitability changes in distributional limits. The detected extent and direction of suitability trends do not suggest the uniform pole-ward or upslope shifts expected under warming conditions. Comparisons between suitability and variable trends suggest that precipitation, not temperature, plays a stronger role in explaining changes in climatic suitability for C. mexicanus. Where precipitation decreased, there was suitability loss, while in areas where precipitation increased, suitability gain was observed. These analyses illustrate how incorporating time-series climatic data into ENMs can aid in understanding if species are already responding to changes in climate. Here, the potential response of C. mexicanus to climate change varies across its distribution and therefore the species' range shifts may not necessarily follow expected general patterns. These findings should be verified with field data. More generally, using the valuable climatic information of the last several decades should be incorporated into studies that determine potential range shifts under recent or future climatic conditions.

The Future of European Beech in Northern Germany—Climate Change Vulnerability and Adaptation Potential

Earth’s forests are increasingly exposed to climate risks through climate change-related drought and heat waves. Here, we review the climate vulnerability of European beech (Fagus sylvatica), the most abundant tree species of Central Europe’s temperate forests, and its adaptation potential to a hotter and drier climate in northern Germany, close to the center of the species’ distribution range. About two-thirds of the studied beech forests show persistent negative growth trends of their dominant trees since the onset of rapid warming in the early 1980s, driven primarily by long-term deterioration of the climatic water balance (CWB) in summer and, locally, long-term decrease in June precipitation. Lower water storage capacity of the soil increases the climate sensitivity of growth. Even though beech populations of drier sub-regions reveal some acclimation to drought (reduced stomatal conductance, turgor loss point reduction, higher C allocation to roots), they are more climate-vulnerable than populations at moister sites, visible in larger growth decreases and greater CWB sensitivity of growth. Even though beech mortality is still lower in the study region than in other parts of Central Europe, our results identify beech forest regions with <350 mm growing-season precipitation as vulnerable to recent climate conditions, which refers to half of the study region. With further climate warming and aridification, most of northern Germany likely will become unfavorable for beech growth within the next tree generation, which suggests choosing in many production forests alternative, more drought- and heat-resistant timber species.

Time to consider the timing of conservation measures: Designing cost-effective agri-environment schemes under climate change

AbstractClimate change is one of the largest threats for biodiversity as changing climatic conditions often make existing habitat sites less suitable. This poses new challenges for species conservation, in particular in agricultural landscapes, where climate change may also induce modifications in agricultural land use. To conserve species in agricultural landscapes, agri-environment schemes (AES) which compensate farmers for implementing conservation measures are commonly used. However, current research on the cost-effective design of AES largely ignores necessary adaptations of conservation measures given climate change. We develop a climate-ecological-economic (CEE) model to examine how the cost-effective design of AES has to be modified under climate change. We apply the model to the conservation of eight meadow bird species in Northern Germany and determine the cost-effective conservation measures under recent and future climatic conditions. We find that the timing of conservation measures in the AES needs to be changed in the RCP8.5 scenario given the species’ phenological adaptations and the impact of extreme events (inundations) on costs. The novelty of the research lies in the development of a CEE model which considers both spatial and temporal changes in costs and benefits to develop recommendations for the cost-effective design of AES under climate change.

Sediment delivery to sustain the Ganges-Brahmaputra delta under climate change and anthropogenic impacts

The principal nature-based solution for offsetting relative sea-level rise in the Ganges-Brahmaputra delta is the unabated delivery, dispersal, and deposition of the rivers’ ~1 billion-tonne annual sediment load. Recent hydrological transport modeling suggests that strengthening monsoon precipitation in the 21st century could increase this sediment delivery 34-60%; yet other studies demonstrate that sediment could decline 15-80% if planned dams and river diversions are fully implemented. We validate these modeled ranges by developing a comprehensive field-based sediment budget that quantifies the supply of Ganges-Brahmaputra river sediment under varying Holocene climate conditions. Our data reveal natural responses in sediment supply comparable to previously modeled results and suggest that increased sediment delivery may be capable of offsetting accelerated sea-level rise. This prospect for a naturally sustained Ganges-Brahmaputra delta presents possibilities beyond the dystopian future often posed for this system, but the implementation of currently proposed dams and diversions would preclude such opportunities.

Pristine levels of suspended sediment in large German river channels during the Anthropocene?

Abstract. Suspended sediment is an integral part of riverine transport and functioning that has been strongly altered during the Anthropocene due to the overwhelming human pressure on soils, sediments, and the water cycle. Understanding the controls of changing suspended sediment in rivers is therefore vital for effective management strategies. Here we present results from a trend analysis of suspended sediments covering 62 monitoring stations along the German waterways (catchment sizes range between 2000 and 160 000 km2) with more than 440 000 water samples taken between 1990 and 2010. Based on daily monitoring of suspended sediment concentration (SSC), we found significant declines in mean annual SSC and annual suspended sediment loads (SSLs) at 49 of 62 monitoring stations totaling −0.92 mg L−1 yr−1. At some stations decreases during the 20 years represent up to 50 % of the long-term average SSC. Significant decreases in SSC are associated with declining SSL despite an increase in sheet and rill erosion by almost 150 % derived from modeling due to changes in land use and management as well as rainfall erosivity. The contemporary suspended sediment loads of the Rhine at the German–Dutch border are approaching the natural base level of ∼1 Mt yr−1, which was reached by the Rhine during the mid-Holocene when the suspended sediment load was adjusted to the Holocene climatic conditions and before the onset of increased loads due to human-induced land use changes in the Rhine catchment. At this point we can only speculate regarding potential reasons for a decline in sediment transport in larger rivers despite erosion increase. We argue that increased sediment retention in upstream headwaters is presumably the major reason for declining SSC in the large river channels studied.

Extreme Hydrometeorological Conditions and Changes in the Amu Darya River Basin in Central Asia

Abstract The Amu Darya contributed 70% of the flow to the Aral Sea in central Asia before the 1960s, when the Amu Darya streamflow to the Aral Sea started to dwindle. The severe environmental and socioeconomic disaster happened mainly due to intensified water abstraction with the backdrop of climate change. However, knowledge of up to the most recent extreme climate conditions and their changes, as well as their relations to streamflow in the basin, is still lacking. This study aims to understand extreme hydrometeorological conditions and their changes, as well as their relations in the past several decades, especially in the upper Amu Darya basin. The spatial patterns of the means of all extreme temperature indices followed the elevation gradient. The majority of the basin showed an increasing trend in extreme warm events but a decreasing trend in extreme cold events. The north of the upper basin had over 1000 mm annual precipitation, and the east had less than 300 mm annual precipitation. Overall, the upper Amu Darya basin underwent a wetting and warming annual trend. Annual streamflow in the upper subbasins was less than 750 m3 s−1, but together they produced over 1500 m3 s−1 flow in the middle reach and basin outlet. Streamflow change varied among subbasins. Correlations between climatic factors and streamflow at annual time steps were weak but distinct at monthly time steps with lagged effects. In highland subbasins with high coverage of glaciers and snow, temperature minima and maxima impacts were opposite and overwhelmed precipitation, whereas in lowland subbasins, precipitation was more important.

Weather potential for high-quality still wine from Chardonnay viticulture in different regions of the UK with climate change

UK viticulture is benefitting from climate change with an increase in vineyard area and a move towards French grapevine varieties, primarily Chardonnay and Pinot noir, to produce sparkling wine. Doubt remains, however, as to how good UK still wine can be from these varieties. The simple Chablis vintage model uses only three climatic indices: mean temperature from April to September, mean minimum temperature in September (cool night index) and total rainfall from June to September. It was applied to the UK for the periods 1981–2000, 2010–2019 and, with climate change projections, to 2040–2059 to locate sites in the UK with the climate potential to produce high-quality Chardonnay still wine. Weather data for 1981–2000 and 2010–2019 were taken from the Met Office’s HadUK-Grid at a resolution of 5 × 5 km, and climate projections for 2040–2059 were derived from UKCP18, using intermediate emission scenario RCP 4.5 at the 5th, 50th and 95th percentile probabilities. Recent and current climatic conditions throughout most of the UK were unsuitable for sustainable production of high-quality still Chardonnay wine (only 0.2 to 1.8 % of UK land area suitable), but model scores corresponded with high-quality Chardonnay still wine production observed in some regions of England in 2018. Under the 5th percentile RCP 4.5 projection for 2040–2059, climatic conditions are similar to 2010–2019 and generally unsuitable for sustainable, high-quality still Chardonnay wine production. Under the median and 95th percentile projections for 2040–2059, however, South East England and East of England have the potential for high-quality still Chardonnay wine production in an average year, and Central England also with the 95th percentile projection. Overall, climate change is expected to benefit the production of high-quality still Chardonnay wine in the medium term, with up to 42.4 % of UK land possibly climatically (but not necessarily agronomically) suitable by mid-century. The model does not account for extreme events, however, and there is uncertainty over future inter-annual weather variability, and so the sustainability of high-quality still wine production. Planting Chardonnay clones suitable for both sparkling and still wines in the most-suitable areas of England would provide flexibility and so resilience.

Lake Chad vegetation cover and surface water variations in response to rainfall fluctuations under recent climate conditions (2000−2020)

Monitoring the evolution of the Sahelian environment is a major challenge because the great Sahelian droughts, marked by significant environmental consequences and social impacts, contributed, for example, to the drying up of Lake Chad. We combined remote sensing images with a water level database from the Hydroweb project to determine the response of Lake Chad vegetation cover and surface water variations to rainfall fluctuations in the Lake Chad watershed under recent climate conditions. The variance in lake surface water levels was determined by computing the monthly anomaly time series of surface water height and area from the Hydroweb datasets. The spatiotemporal variability of watershed rainfall and vegetation cover of Lake Chad was highlighted through multivariate statistical analysis. The spatial distribution of correlations between watershed rainfall and Lake Chad vegetation cover was investigated. The results show an increase in watershed rainfall, vegetation cover, and surface water area and height, as their slopes were all positive i.e., 5.1 10−4 (mm/day); 4.26 10−6 (ndvi unit/day); 1.2 10−3 (km2/day) and 6 10−5 (m/day), respectively. The rainfall variations in the watershed drive those of Lake Chad vegetation cover and surface water, as the rainfall trend was strongly and positively correlated with those of vegetation cover (0.79), surface water height (0.57), and area (0.53). The time lag between the watershed rainfall fluctuations and lake surface water variations corresponded to approximately ∼112 days. Between rainfall variations and vegetation cover changes, the spatial distribution of the time lag showed a response time of <16 days in the western shores of the lake and on both sides of the great barrier, about 16 days in the bare soils of the northern basin and the eastern part of the south basin, and >64 days in the marshlands of the southern basin. For the analysis of lakes around the world, this research provides a robust method that computes the spatiotemporal variances of their trends and seasonality and correlates these with the spatiotemporal variances of climate changes. The correlations obtained have strong potential for predicting future changes in lake surface water worldwide.