Present-day Values Research Articles (Page 1)

Abstract. Although well-researched in the present climate, it is poorly understood how Rossby wave breaking (RWB) may change in a warmer future climate. In this study, we examine how large changes in sea ice cover (SIC) and sea surface temperature (SST) affect the frequency and spatial distribution of Rossby wave breaking in the Northern Hemisphere during the boreal winter (December–February) and summer (June–August) seasons. Our experiment setup consists of eight 40-year atmosphere-only simulations from two models (OpenIFS and EC-Earth) that use different combinations of prescribed present-day and future SIC and SST values under the SSP5-8.5 scenario. We find present-day RWB frequencies that correspond well with previous literature. Our models are generally in good agreement with regards to the spatial distribution of RWB. The effects of SSP5-8.5 SST on RWB are substantial, while simulations using future SIC and present-day SSTs do not exhibit statistically significant changes compared to the present. In simulations with SST changes, anticyclonic wave breaking (AWB) frequencies show large decreases during both winter and summer, while the primary changes to cyclonic wave breaking (CWB) are small increases of varying magnitude in winter. The winter changes are notably collocated with changes in the strength and location of jet streams. The largest changes occur over the North Pacific, where winter AWB decrease by 60 %–70 % over the East Pacific and summer AWB decrease by roughly 50 % over the West Pacific and East Asia. Over the western North Atlantic, decreases of 10 %–30 % in winter AWB are collocated with a stronger eddy-driven jet, which may suggest an eastward shift in AWB. In summer, AWB decreases by about 50 % over North America but increases slightly over Europe. As with related previous studies of future changes in blocking and jet stream waviness, there are uncertainties in our results, and especially determining the impact of SIC changes likely requires longer simulations than those used in this study. This study demonstrates that particularly SST changes are an important component for changes to RWB in future climates.

Abstract. The proportionality between global mean temperature and cumulative emissions of CO2 predicted in Earth system models (ESMs) is the foundation of carbon budgeting frameworks. Deviations from this behavior could impact estimates of required net-zero timings and negative emissions requirements to meet the Paris Agreement climate targets. However, existing ESM diagnostic experiments do not allow for direct estimation of these deviations as a function of defined emissions pathways. Here, we perform a set of climate model diagnostic experiments for the assessment of transient climate response to cumulative CO2 emissions (TCRE), the Zero Emissions Commitment (ZEC), and climate reversibility metrics in an emissions-driven framework. The emissions-driven experiments provide consistent independent variables simplifying simulation, analysis and interpretation, with emissions rates more comparable to recent levels than existing protocols using model-specific compatible emissions from the CMIP DECK 1pctCO2 experiment, where emissions rates tend to increase during the experiment, such that at the time of CO2 doubling in year 70, emissions are much greater than present-day values. A base experiment, “esm-flat10”, has constant emissions of CO2 of 10 GtC per year (near-present-day values), and initial results show that the TCRE estimated in this experiment is about 0.1 K less than that obtained using 1pctCO2. A subset of ESMs exhibit land carbon sinks that saturate during this experiment. A branch experiment, esm-flat10-zec, illustrates that both positive and negative ZEC effects are less pronounced under esm-flat10 than under 1pctCO2 – the magnitude of ZEC50 in ESMs is, on average, reduced by 30 % compared with 1pctCO2 branch experiments. A final experiment, esm-flat10-cdr, assesses climate reversibility under negative emissions, where we find that peak warming may occur before or after net zero and that the asymmetry in temperature at a given level of cumulative emissions between the positive and negative emissions phases is well described by ZEC in most models. Further, we find that existing probabilistic simple climate model (SCM) ensembles tend to overestimate temperature reversibility compared with ESMs, highlighting the need for additional constraints. We propose a set of climate diagnostic indicators to quantify various aspects of climate reversibility. These experiments were suggested as potential candidates in CMIP7 and have since been adopted as “fast track” simulations.

Abstract Several, more recent global warming projections in the coupled model intercomparison project 6 contain extensions beyond year 2100–2300/2500. The Atlantic meridional overturning circulation (AMOC) in these projections shows transitions to extremely weak overturning below the surface mixed layer (<6 Sv; 1 Sv = 106 m3 s−1) in all models forced by a high-emission (SSP585) scenario and sometimes also forced by an intermediate- (SSP245) and low-emission (SSP126) scenario. These extremely weak overturning states are characterised by a shallow maximum overturning at depths less than 200 m and a shutdown of the circulation associated with North Atlantic deep water formation. Northward Atlantic heat transport at 26°N decreases to 20%–40% of the current observed value. Heat release to the atmosphere north of 45°N weakens to less than 20% of its present-day value and in some models completely vanishes, leading to strong cooling in the subpolar North Atlantic and Northwest Europe. In all cases, these transitions to a weak and shallow AMOC are preceded by a mid-21st century collapse of maximum mixed-layer depth in Labrador, Irminger and Nordic Seas. The convection collapse is mainly caused by surface freshening from a decrease in northward salt advection due to the weakening AMOC but is likely initiated by surface warming. Maximum mixed-layer depths in the observations are still dominated by internal variability but notably feature downward trends over the last 5–10 years in all deep mixing regions for all data products analysed. This could be merely variability but is also consistent with the model-predicted decline of deep mixing.

The organic geochemistry and organic carbon structures of gas-producing shale reservoirs were investigated from the Silurian Longmaxi Formation of the Weiyuan Block, Sichuan Basin, by the total organic carbon (TOC) measurement, Rock-Eval pyrolysis, and scanning electron microscopy/transmission electron microscopy (SEM/TEM) image analyses. The purpose of this article is to provide awareness of the nature and complexity in organic carbon structures within overmature shales and to provide an organic geochemical evaluation on the gas-producing reservoirs. Present-day TOC values range from 0.07 to 8.2 wt % (2.17 wt % on average), which primarily reside in type IV kerogen (inert solid bitumen and porous pyrobitumen). From the Rock-Eval pyrolysis data, the shales are found to be overmatured, with an average calculated R o value of 2.71%. Most samples have low-pyrolysis S 2 peaks and present-day hydrogen index (HI), with an average of 0.19 mg of hydrocarbons (HC)/g of rock and 20.47 mg of HC/g of TOC, respectively, indicating little present-day hydrocarbon generative potential from the remaining organic matter. SEM and TEM high-resolution (∼0.5 nm) image analysis not only provides a visual appreciation of the shale organic carbon structure but also can provide a semiquantitative method to calculate the carbon layer spacing and size of organic nanopores and "onion-like'' concentric organic particles. SEM and TEM images highlight complex organic carbon structures in overmature shales at the micro- and nanoscale. A large number of turbostratic carbon nanostructures result from hydrocarbon generation and are considered to be the end products of the thermal evolution of organic matter. Confirming their origin and abundance provides a key geological indicator for assessing thermal maturity evolution and identifying promising overmature shale gas exploration targets in analogous basins.

Abstract In the past two decades, transit surveys have revealed a class of planets with thick atmospheres—sub-Neptunes—that must have completed their accretion in protoplanet disks. When planets form in the gaseous disk, the gravitational interaction with the disk gas drives their migration and results in the trapping of neighboring planets in mean motion resonances, though these resonances can later be broken when the damping effects of disk gas or planetesimals wane. It is widely accepted that the outer solar system gas-giant planets originally formed in a resonant chain, which was later disrupted by dynamical instabilities. Here, we explore whether the early formation of the terrestrial planets in a resonance chain (including Theia) can evolve to the present configuration. Using N-body simulations, we demonstrate that the giant planet instability would also have destabilized the terrestrial resonance chain, triggering Moon-forming giant impacts in 20%–50% of our simulated systems, dependent on the initial resonance architecture. After the instability, the eccentricity and inclination of the simulated planets match their present-day values. Under the proposed scenario, the current period ratio of 3.05 between Mars and Venus—devoid of any special significance in traditional late-formation models—naturally arises as a relic of the former resonance chain.

The study investigates the geostress characteristics and fracturing countermeasures in a low-permeability sandstone reservoir within the YP1 well area of the Songliao Basin. The reservoir exhibits multiple layers, thin individual layer thicknesses, and a concentrated oil-bearing section, posing challenges for development. To address these complexities, the research utilizes seismic, well logging, and hydraulic fracturing data to calculate key parameters for ground stress field simulation. The study proceeds in three stages: simulation of the present-day tectonic stress field and classification of deformation medium types; depth-slice-based simulation of the present-day tectonic stress field for each layer; and establishment of a 3D stress model using Petrel software. This model allows for the analysis of the spatial distribution of the tectonic stress field and the identification of spatial variation rules within the YP1 well area’s present-day tectonic stress differential stress values. These findings provide a foundation for optimizing layer selection in vertical well fracturing projects within low-permeability reservoirs. Furthermore, the study examines the stress state of the straight wellbore in the YP1 well zone, proposes corresponding fracturing methods based on distinct stress states, and evaluates the fracturing effects observed in the YP1-4 and YP1-5 wells. These insights offer valuable support for the large-scale development of the YP1 well zone and the strategic deployment of horizontal wells.

We present a study of the evolution of star-forming galaxies within what is known as the Wall structure at z∼0.73 in the field of the COSMOS survey. We use a sample of star-forming galaxies from a comprehensive range of environments and across a wide stellar mass range. We discuss the correlation between the environment and the galaxy's internal properties, including its metallicity from the present-day gas-phase value and its past evolution as imprinted in its stellar populations. We measured emission-line fluxes from the stacked spectra of galaxies selected within small stellar mass bins and in different environments. These fluxes were then converted to gas-phase metallicities. In addition, we built a simple yet comprehensive galaxy chemical evolution model, which is constrained by the gas-phase metallicities, stacked spectra, and photometry of galaxies to reach a full description of the galaxies' past star formation and chemical evolution histories in different environments. Parameters derived from best-fit models provide insights into the physical process behind the evolution. We reproduce the downsizing formation of galaxies in their star formation histories and in their chemical evolution histories at z∼0.73 so that more massive galaxies tend to grow their stellar mass and become enriched in metals earlier than less massive ones. In addition, the current gas-phase metallicity of a galaxy and its past evolution correlate with the environment it inhabits. Galaxies in groups, especially massive groups that have X-ray counterparts, tend to have higher gas-phase metallicities and are enriched in metals earlier than field galaxies of similar stellar mass. Galaxies in the highest stellar mass bin and located in X-ray groups exhibit a more complex and varied chemical composition. The evolution of a galaxy, including its star formation history and chemical enrichment history, exhibits a notable dependence on the environment where the galaxy is located. This dependence is revealed in our sample of star-forming galaxies in the Wall region at a redshift of z∼0.73. Strangulation due to interactions with the group environment, leading to an early cessation of gas supply, may have driven the faster mass growth and chemical enrichment observed in group galaxies. Additionally, the removal of metal-enriched gas could play a key role in the evolution of the most massive galaxies. Alternative mechanisms other than environmental processes are also discussed.

Obliquity and precession forcing of the amplitude of millennial-scale East Asian monsoon variability during the late Miocene.

Appraisal of gold production and trade via Artisanal and Small-Scale Mining (ASM) in Tanzania has been achieved through assessing the literature and onsite interviews. Authors settle on the understanding that ASM is extricated to Industrial Mining (IM) upon funding, informality, and applications of technology. However, ASM has been embraced in Tanzania pre-to post-independence based on two facts: i) its gold production in the primordial period made a gateway to export trade, and ii) ASM was a feasible means of gold production in periods of insufficient infrastructures and geo-political and economic challenges. Gold produced via ASM worth £363,084,500 equivalent to Sh. 1,194.3 billion (in present-day values) was recorded during the German colonial administration (1886-1920). For the British colonial administration (1920-1961), gold worth of £169,854,560 equivalent to Sh. 558.7 billion was produced. Smuggling and illegal markets obscured the amount of gold produced and traded immediately after independence. However, two years after the establishment of the local mineral markets (2019 – 2021), Government’s collection from ASM gold sales rose from Sh. 61.53 billion to Sh.154.49 billion making 151.08% increase. In 2021, gold ASM contributed 2.6% to the GDP implying that, ASM holds a great potential of contributing significantly to the social-economic development of the resource-rich developing countries. Tanzania has worked to formalize ASM legally, and through the establishment of demonstration centers, demarcating sites, oversight, and mineral markets. Nevertheless, lack of access to loans because of bankers’ stringent conditions deters its growth. Therefore, it is imminent for scholars to research on appropriate mechanisms of ASM financing, and for the government to institute policy changes that will recognize Primary Mining Licenses (PMLs) as assets, to help alleviate the problems with lending practices and enhance ASM’s economic contribution.

Net Present Value (NPV) is a cornerstone of financial decision-making, allowing us to assess the profitability of certain investment by discounting future cash flows to their present-day value. However, what if we need to project the future value of an investment, taking into account inflation and the inherent uncertainty of the future? This article explores how to move beyond NPV to estimate future value, incorporating real interest rates and modelling uncertainty.

Weather conditions in southern Poland at the turn of the 20th century — Insights from archived observational records

Abstract This article examines the olive tree as an aspect of the Portuguese landscape. After considering the notion of landscape as a concept, it traces references to olive tree cultivation and olive oil production, particularly within the Iberian context, from Antiquity through the twenty-first century. It argues that these practices form an important and understudied in the history of knowledge transmission, particularly what has been lately termed “artisanal knowledge.” It likewise points to the potential present-day value of recovering traditional practices for the future of industries connected to the olive tree in Portugal.

Mudstone diagenesis in the Cenomanian–Turonian Eagle Ford Group in the San Marcos Arch area. PART I: Chemostratigraphy, early diagenesis, bitumen expulsion and migration pathways

Anthropogenic emissions alter atmospheric composition and therefore the climate, with implications for air pollution- and climate-related human health. Mortality attributable to air pollution and non-optimal temperature is a major concern, expected to shift under future climate change and socioeconomic scenarios. In this work, results from numerical simulations are used to assess future changes in mortality attributable to long-term exposure to both non-optimal temperature and air pollution simultaneously. Here we show that under a realistic scenario, end-of-century mortality could quadruple from present-day values to around 30 (95% confidence level:12-53) million people/year. While pollution-related mortality is projected to increase five-fold, temperature-related mortality will experience a seven-fold rise, making it a more important health risk factor than air pollution for at least 20% of the world’s population. These findings highlight the urgent need to implement stronger climate policies to prevent future loss of life, outweighing the benefits of air quality improvements alone.

Abstract. Tropical tropospheric ozone (TTO) is important for the global radiation budget because the longwave radiative effect of tropospheric ozone is higher in the tropics than midlatitudes. In recent decades the TTO burden has increased, partly due to the ongoing shift of ozone precursor emissions from midlatitude regions toward the Equator. In this study, we assess the distribution and trends of TTO using ozone profiles measured by high-quality in situ instruments from the IAGOS (In-Service Aircraft for a Global Observing System) commercial aircraft, the SHADOZ (Southern Hemisphere ADditional OZonesondes) network, and the ATom (Atmospheric Tomographic Mission) aircraft campaign, as well as six satellite records reporting tropical tropospheric column ozone (TTCO): TROPOspheric Monitoring Instrument (TROPOMI), Ozone Monitoring Instrument (OMI), OMI/Microwave Limb Sounder (MLS), Ozone Mapping Profiler Suite (OMPS)/Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2), Cross-track Infrared Sounder (CrIS), and Infrared Atmospheric Sounding Interferometer (IASI)/Global Ozone Monitoring Experiment 2 (GOME2). With greater availability of ozone profiles across the tropics we can now demonstrate that tropical India is among the most polluted regions (e.g., western Africa, tropical South Atlantic, Southeast Asia, Malaysia and Indonesia), with present-day 95th percentile ozone values reaching 80 nmol mol−1 in the lower free troposphere, comparable to midlatitude regions such as northeastern China and Korea. In situ observations show that TTO increased between 1994 and 2019, with the largest mid- and upper-tropospheric increases above India, Southeast Asia, and Malaysia and Indonesia (from 3.4 ± 0.8 to 6.8 ± 1.8 nmol mol−1 decade−1), reaching 11 ± 2.4 and 8 ± 0.8 nmol mol−1 decade−1 close to the surface (India and Malaysia–Indonesia, respectively). The longest continuous satellite records only span 2004–2019 but also show increasing ozone across the tropics when their full sampling is considered, with maximum trends over Southeast Asia of 2.31 ± 1.34 nmol mol−1 decade−1 (OMI) and 1.69 ± 0.89 nmol mol−1 decade−1 (OMI/MLS). In general, the sparsely sampled aircraft and ozonesonde records do not detect the 2004–2019 ozone increase, which could be due to the genuine trends on this timescale being masked by the additional uncertainty resulting from sparse sampling. The fact that the sign of the trends detected with satellite records changes above three IAGOS regions, when their sampling frequency is limited to that of the in situ observations, demonstrates the limitations of sparse in situ sampling strategies. This study exposes the need to maintain and develop high-frequency continuous observations (in situ and remote sensing) above the tropical Pacific Ocean, the Indian Ocean, western Africa, and South Asia in order to estimate accurate and precise ozone trends for these regions. In contrast, Southeast Asia and Malaysia–Indonesia are regions with such strong increases in ozone that the current in situ sampling frequency is adequate to detect the trends on a relatively short 15-year timescale.

The Parameterised Post-Newtonian (PPN) approach is the default framework for performing precision tests of gravity in nearby astrophysical systems. In recent works we have extended this approach for cosmological applications, and in this paper we use observations of the anisotropies in the Cosmic Microwave Background to constrain the time variation of the PPN parameters α and γ between last scattering and the present day. We find their time-averages over cosmological history should be within ∼ 20% of their values in GR, with α̅= 0.89+0.08 -0.09 and γ̅ = 0.90+0.07 -0.08 at the 68% confidence level. We also constrain the time derivatives of these parameters, and find that their present-day values should be within a factor of two of the best Solar System constraints. Many of these results have no counter-part from Solar System observations, and are entirely new constraints on the gravitational interaction. In all cases, we find that the data strongly prefer α̅ ≃ γ̅, meaning that observers would typically find local gravitational physics to be compatible with GR, despite considerable variation of α and γ being allowed over cosmic history. This study lays the groundwork for future precision tests of gravity that combine observations made over all cosmological and astrophysical scales of length and time.

Seismic life-cycle cost analysis (SLCCA) is a comprehensive tool to estimate the expected lifetime economic losses due to seismic events in terms of present-day value and aids in lifetime investment planning and design decision-making. The state-of-the-art framework for SLCCA incorporates three essential components: seismic hazard analysis, seismic fragility curves and damage cost estimates. Due to different sources of uncertainty prevailing in each component, the SLCC estimates may vary substantially. However, most of the existing literature primarily focuses on the expected value of the SLCC, and uncertainties stemming from multiple sources are unaccounted for. To address this drawback, this study proposes a comprehensive approach to quantify and propagate multiple uncertainties and offers a visualization of the shape and nature of SLCC distribution. Furthermore, the application of the framework is demonstrated using a case study example of the reinforced concrete (RC) frame building. Results reveal that the SLCC distribution is multimodal due to multiple uncertainty sources and the expected SLCC values also shift significantly compared to the state-of-the-art approaches, highlighting the criticality of the uncertainty propagation. Lastly, a novel framework is proposed to rank uncertainty sources based on their relative influence that will aid stakeholders in informed decision-making under uncertainty.

Climate and vegetation changes in southern Primorye (Russian Far East) since the Last Glacial Maximum: A quantitative analysis

The article addresses the present-day cultural and value agendas of the USA and the Russian Federation within the context of political confrontation between the two state paradigms. The historical and philosophical context of the postmodern value course of the USA and traditional value orientations of the Russian Federation is analyzed. It also presents a dialectical forecast regarding the potential for overcoming the current value cleavage between the two countries.

Rising organic charge in northern freshwaters is attributed to increasing levels of dissolved natural organic matter (DNOM) and changes in water chemistry. Organic charge concentration may be determined through charge balance calculations (Org.−) or modelled (OAN−) using the Oliver and Hruška conceptual models, which are based on the density of weak acid functional sites (SD) present in DNOM. The charge density (CD) is governed by SD as well as protonation and complexation reactions on the functional groups. These models use SD as a key parameter to empirically fit the model to Org.−. Utilizing extensive water chemistry datasets, this study shows that spatial and temporal differences in SD and CD are influenced by variations in the humic-to-fulvic ratio of DNOM, organic aluminum (Al) complexation, and the mole fraction of CD to SD, which is governed by acidity. The median SD values obtained for 44 long-term monitored acid-sensitive lakes were 11.1 and 13.9 µEq/mg C for the Oliver and Hruška models, respectively. Over 34 years of monitoring, the CD increased by 70%, likely due to rising pH and declining Al complexation with DNOM. Present-day median SD values for the Oliver and Hruška models in 16 low-order streams are 13.8 and 15.8 µEq/mg C, respectively, and 10.8 and 12.5 µEq/mg C, respectively, in 10 high-order rivers.