62880 research outputs found
Sort by
Uncertainties in the Arctic Ocean response to CO₂: a process-based analysis
Get PDFUsing an ensemble of atmosphere–ocean general circulation models (AOGCMs) in an idealized climate change experiment, this study evaluates the contribution of different ocean processes to Arctic Ocean warming. On the AOGCM-mean, the Arctic Ocean warming is greater than the global ocean warming, both in the volume-weighted mean, and at most depths within the upper 2000 m. However, the uncertainty of Arctic Ocean warming is much larger than the uncertainty of global ocean warming. The Arctic warming is greatest a few 100 m below the surface and is dominated by the import of extra heat, which is added to the ocean at lower latitudes and is conveyed to the Arctic mostly by the large-scale barotropic ocean circulation. The change in strength of this circulation in the North Atlantic is relatively small and not correlated with the Arctic Ocean warming. The Arctic Ocean warming is opposed and substantially mitigated by the weakening of the Atlantic meridional overturning circulation (AMOC), though the magnitude of this effect has a large model spread. By reducing the northward transport of heat, the AMOC weakening causes a redistribution of heat from high latitudes to low latitudes. Within the Arctic Ocean, the propagation of heat anomalies is influenced by broadening of cyclonic circulation in the east and weakening of anticyclonic circulation in the west. On the model-mean, the Arctic Ocean warming is most pronounced in the Eurasian Basin, with large spread across the AOGCMs, and accompanied by subsurface cooling by diapycnal mixing and heat redistribution by mesoscale eddies
A review of the effects of mushrooms on mood and neurocognitive health across the lifespan
Get PDFMushrooms contain bioactive compounds with documented antioxidant and anti-inflammatory actions. Here, we present a systematic evaluation of epidemiological and clinical studies that investigate the role of mushrooms, either as a separate or integral dietary component, on neurocognition and mood. Following a search of four databases, a total of 34 human studies examining the effect of different mushrooms across varying age cohorts and health statuses were selected for inclusion. Epidemiological studies included in this review (n = 24) revealed a significant benefit of dietary patterns that included mushrooms of any species on cognition and mood in both healthy and compromised populations. However, the results obtained from intervention studies (n = 10) were mixed. Studies mainly investigated Lion’s Mane (Hericium erinaceus), showing some enhancement of mood and
cognitive function in middle-aged and older adults. Further acute and chronic human intervention studies are needed, using adequate sample sizes, employing appropriately sensitive neurocognitive tests, and investigating a range of dietary mushrooms, to confirm the effects of mushroom supplementation on neurocognition and mood in humans
The impact of plants on the humidity of naturally-ventilated office indoor environments
Get PDFThis study investigated the seasonal impact of indoor plants on the humidity and air temperature of three naturally-ventilated, unoccupied offices, with low air exchange rates. The introduction of 12 Ficus or 6 Epipremnum plants resulted in a small but significant increase in the office’s (28 m3) moisture content, measured every 5 minutes for 24-hour periods for up to six test days during spring and winter, compared to the days without plants. Depending on the season, plants emitted between 35 g (in winter) and 68 g (in summer) of moisture via evapo-transpiration (ET), per plant, per day. In summer, however, due to higher room air exchange rates, we did not detect significant impact of plants despite higher plants’ ET rates. Most of the moisture emitted from the plants in all seasons was removed through room air exchange and moisture sorption. Air exchange rate had a greater impact on indoor RH than plants.
Additional controlled-environment chamber studies showed there is a significant difference in the humidification capacity between five different indoor plant species. Leafy Epipremnum had the highest ET rate under all tested environmental conditions and would have the greatest humidification potential for indoor environments. Succulent Sansevieria had the lowest ET rate, not significantly higher than bare substrate; this species would present a good choice for environments where a low moisture contribution is required. ET rates were highest at low ambient humidity and high temperatures; thus, the greatest water vapour contribution by plants would be made to hot, dry indoor environments and lower in cool rooms with high humidity levels
Essays on measures of risk in finance
Get PDFThis thesis explores financial risk measurement, specifically addressing market
risk, climate transition risk, and credit risk, which are organized into three main
chapters.
The first contribution is that it proposes to estimate Value-at-Risk (VaR) and
Expected Shortfall (ES) at extreme levels using information from a common level.
We employ time series cross-validation to optimize the forecasting performance.
Our simulation study reveals that the proposed novel models outperform the
original Generalized Autoregressive Score model of Patton et al. (2019) according
to various backtests. Empirical evidence based on the return data of four oil
futures also shows the superior performance of the proposed models. Notably,
our models’ performance is most prominent during the COVID-19 period.
The second contribution is that it provides a framework to measure the effects of climate transition risk factors, proxied by the environmental pillar of
ESG scores, on corporate downside risk. Analyzing the stock returns and climate
risk factors relationship, a notable negative correlation in lower quantiles is revealed. A new risk measure for climate transition risk factors is also proposed,
with empirical findings indicating sector-based variations in sensitivity to these
risks. Specifically, the Health Care sector is the least efficient in reducing climate
risk, while the Energy sector benefits the most from improvements in the firms’
environmental scores.
The third contribution is a study examining how corporate environmental
performance influences credit ratings, with a trans-Atlantic study encompassing
firms from the United States (US) and the European Union (EU). We find that
corporate environmental performance positively affects the firms’ credit ratings.
Interestingly, our findings reveal a linear relationship in the US and a nonlinear
one in the EU. These findings highlight the implications of environmental performance. They provide vital insights for firms aiming to improve their credit rating
via sustainability initiatives, while considering regional disparities
Added value of seasonal hindcasts to create UK hydrological drought storylines
Get PDFThe UK has experienced recurring periods of hydrological droughts in the past, including the drought declared in summer 2022. Seasonal hindcasts, consisting of a large sample of plausible weather sequences, can be used to create drought storylines and add value to existing approaches to water resources planning. In this study, the drivers of winter rainfall in the Anglian region in England are investigated using the ECMWF SEAS5 hindcast dataset, which includes 2850 plausible winters across 25 ensemble members and 3 lead times. Four winter clusters are defined using the hindcast winters based on possible combinations of various atmospheric circulation indices (such as North Atlantic Oscillation (NAO), East Atlantic (EA) pattern and the El-Niño Southern Oscillation). Using the 2022 drought as a case study, we demonstrate how storylines representing alternative ways the event could have unfolded can be used, to explore plausible worst cases over winter 2022/23 and beyond. The winter clusters span a range of temperature and rainfall response in the study region and represent circulation storylines that could have happened over winter 2022/23. River flow and groundwater level simulations with the large sample of plausible hindcast winters show that drier than average winters characterised by predominantly NAO-/EA- and NAO+/EA- circulation patterns could have resulted in the continuation of the drought with a high likelihood of below normal to low river flows across all selected catchments and boreholes by spring and summer 2023. Catchments in Norfolk were particularly vulnerable to a dry summer in 2023 as river flows were not estimated to recover to normal levels even with wet winters characterised predominantly by NAO-/EA+ and NAO+/EA+ circulation patterns, due to insufficient rainfall to overcome previous dry conditions and the slow response nature of groundwater-dominated catchments. Through this analysis, we aim to demonstrate the added value of this approach to create drought storylines during an ongoing event. Storylines constructed in this way supplement traditional weather forecasts and hydrological outlooks to explore a wider range of plausible outcomes
Distribution of infectious and parasitic agents among three sentinel bee species across European agricultural landscapes
Get PDFInfectious and parasitic agents (IPAs) and their associated diseases are major environmental stressors that jeopardize bee health, both alone and in interaction with other stressors. Their impact on pollinator communities can be assessed by studying multiple sentinel bee species. Here, we analysed the field exposure of three sentinel managed bee species (Apis mellifera, Bombus terrestris and Osmia bicornis) to 11 IPAs (six RNA viruses, two bacteria, three microsporidia). The sentinel bees were deployed at 128 sites in eight European countries adjacent to either oilseed rape fields or apple orchards during crop bloom. Adult bees of each species were sampled before their placement and after crop bloom. The IPAs were detected and quantified using a harmonised, high-throughput and semi-automatized qPCR workflow. We describe differences among bee species in IPA profiles (richness, diversity, detection frequencies, loads and their change upon field exposure, and exposure risk), with no clear patterns related to the country or focal crop. Our results suggest that the most frequent IPAs in adult bees are more appropriate for assessing the bees' IPA exposure risk. We also report positive correlations of IPA loads supporting the potential IPA transmission among sentinels, suggesting careful consideration should be taken when introducing managed pollinators in ecologically sensitive environments
A novel free-air diesel and ozone enrichment (FADOE) research platform
Get PDFAir pollution is an escalating concern in the modern world, posing substantial threats to ecosystems processes. While the importance of comprehending the impact of pollutants on natural environments is evident, conducting rigorous field-based experiments presents formidable challenges. Elevating pollutant concentrations within open air environments in a controlled manner is complex. Nonetheless, such real-world experiments are invaluable for revealing the genuine influence of air pollutants on ecosystems and their functioning. Field-scale measurements have emerged as a pivotal avenue for advancing our understanding of the interactions between air pollutants and the natural world, providing unique insights into ecosystem dynamics, including critical processes like pollination and natural pest regulation. In atmospheric and ecological research, free-air exposure systems have proven effective in elevating carbon dioxide (CO2) and ozone (O3) concentrations, facilitating the exploration of their ecological consequences. Yet, nitrogen oxides (NOx), a class of pollutants with significant ecological and atmospheric relevance, have largely eluded field-based ecological investigations. This paper introduces the recently developed FADOE (Free-Air Diesel and Ozone Enrichment) platform, which allows the elevation of O3 and diesel exhaust (including NOx) within a field-scale context. Comprehensive information on the system's design, construction, and performance data from the 2023 summer season is presented
Can gardeners identify ‘future invaders’?
Get PDFIt is estimated that there are 30 million gardeners in Britain, who could play a crucial role in being the ‘first contact’ for reporting ornamental plants in gardens with invasive potential. Invasive species are one of the five drivers of the global nature crisis, many of which were originally introduced through ornamental horticulture. Ornamentals confined to gardens and those which have already naturalised, but are not yet shown to be invasive, represent a ‘pool’ of species with invasive potential – ‘future invaders’. An online survey asking gardeners to report ornamentals they had noticed invading or taking over their garden resulted in 251 different taxa being reported (including cultivars). The future invaders were prioritised with a simple yet structured scheme, looking at the domestic and global naturalised and invasive status of each taxon, including in the Global Register of Introduced and Invasive Species (GRIIS) and the Global Naturalized Alien Flora (GloNAF) databases. The structured scheme identified a shortlist of nine ornamentals of concern which should be prioritised for further analysis, such as a formal risk assessment. Identifying and preventing future invaders before they escape gardens is critical, to prevent future threats to nature. There is also a gap in the identification of potentially invasive ornamentals, which are not currently invasive, yet are beyond the scope of formal horizon scanning because they are naturalised. Here we explore whether surveying gardeners can be a suitable approach to prioritising future invaders while also being an opportunity to increase awareness of invasive species. This positive feedback loop between gardeners and invasion scientists could help reduce the risk of future invaders
Probabilistic causal network modelling of Southern Hemisphere jet sub-seasonal to seasonal predictability
Get PDFSkilful prediction of the Southern Hemisphere (SH) eddy-driven jet is crucial for representation of mid-to-high latitude SH climate variability. In the austral spring-to-summer months, the jet and the stratospheric polar vortex variabilities are strongly coupled. Since the vortex is more predictable and influenced by long-lead drivers one month or more ahead, the stratosphere is considered a promising pathway for improving forecasts in the region on subseasonal
to seasonal (S2S) timescales. However, a quantification of this predictability has been lacking, as most modelling studies address only one of the several interacting drivers at a time, while statistical analyses quantify association but not skill. This methodological gap is addressed through
a knowledge-driven probabilistic causal network approach, quantified with seasonal ensemble hindcast data. The approach enables to quantify the jet’s long-range predictability arising from known late-winter drivers, namely El Ni˜no Southern Oscillation, Indian Ocean Dipole, upward wave activity flux and polar night jet oscillation, mediated by the vortex variability in spring. Network-based predictions confirm the vortex as determinant for skilful jet predictions, both for the jet’s poleward shift in late spring and its equatorward shift in early summer. ENSO, IOD,
late-winter wave activity flux and polar night jet oscillation only provide moderate prediction skill to the vortex. This points to early spring sub-monthly variability as important for determining the vortex state leading up to its breakdown, creating a predictability bottle-neck for the jet. The method developed here offers a new avenue to quantify the predictability provided by multiple,
interacting drivers on S2S timescales
Fresh and recirculated submarine groundwater discharge zones along the central west coast of India
No full textThe study area receives an average of 2840.0 mm of rainfall within four months every year. A portion of the rainwater is flown to the sea as surface water, and the other part is percolated into the bottom as groundwater. In coastal aquifers, the groundwater is transported to the sea due to a hydraulic gradient, and it contains a significant quantity of dissolved materials and nutrients. SGD processes impact the ocean productivity, mangrove and coral growth, local acidification and many. To isolate the SGD on the central west coast of India, different data was referred. The GWL concerning MSL contributed significantly to demarcating the SGD zones by considering the positive (>0 m) and negative (<0 m) values of GWL concerning above MSL. Thermal images for SST of pre-monsoon and post-monsoon periods of 2020 exhibit cooler surrounded by warmer, which might be the SGD buffering zones in the off-central west coast of India. By considering the results from GWL and SST, 8 SGD beach sites were identified for the further particularized study. The water samples were collected in March 2022, and analyzed using standard procedures and instruments. Fresh and mixing (recirculated) zones have been isolated by piper, hydrochemical facies evolution, and Ca +Mg /K +Na Vs log Cl ionic ratio plots. The aquifer water chemical elements are converting possibly due to ionic exchange processes. The decrease in salinity and conductivity observed in the pore water just below the seawater might be due to the influence of freshwater inputs, helping to isolate the fresh SGD and recirculated SGD zones in the study area. Among 8 sites, 3 were found to be fresh SGD sites and 5 were noticed to be mixing/recirculated SGD sites. Most of these Beaches are bounded by hills, which helps to lead the SGD along the central west coast of India