While controls over the Earth's climate system have undergone rigorous hypothesis-testing since the 1800s, questions over the scientific consensus of the role of human activities in modern climate change continue to arise in public settings. We update previous efforts to quantify the scientific consensus on climate change by searching the recent literature for papers sceptical of anthropogenic-caused global warming. From a dataset of 88125 climate-related papers published since 2012, when this question was last addressed comprehensively, we examine a randomized subset of 3000 such publications. We also use a second sample-weighted approach that was specifically biased with keywords to help identify any sceptical peer-reviewed papers in the whole dataset. We identify four sceptical papers out of the sub-set of 3000, as evidenced by abstracts that were rated as implicitly or explicitly sceptical of human-caused global warming. In our sample utilizing pre-identified sceptical keywords we found 28 papers that were implicitly or explicitly sceptical. We conclude with high statistical confidence that the scientific consensus on human-caused contemporary climate change—expressed as a proportion of the total publications—exceeds 99% in the peer reviewed scientific literature.
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Environmental Research Letters covers all of environmental science, providing a coherent and integrated approach including research articles, perspectives and review articles.
R B Jackson et al 2024 Environ. Res. Lett. 19 101002
Mark Lynas et al 2021 Environ. Res. Lett. 16 114005
John Cook et al 2013 Environ. Res. Lett. 8 024024
We analyze the evolution of the scientific consensus on anthropogenic global warming (AGW) in the peer-reviewed scientific literature, examining 11 944 climate abstracts from 1991–2011 matching the topics 'global climate change' or 'global warming'. We find that 66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming. Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming. In a second phase of this study, we invited authors to rate their own papers. Compared to abstract ratings, a smaller percentage of self-rated papers expressed no position on AGW (35.5%). Among self-rated papers expressing a position on AGW, 97.2% endorsed the consensus. For both abstract ratings and authors' self-ratings, the percentage of endorsements among papers expressing a position on AGW marginally increased over time. Our analysis indicates that the number of papers rejecting the consensus on AGW is a vanishingly small proportion of the published research.
Seth Wynes and Kimberly A Nicholas 2017 Environ. Res. Lett. 12 074024
Current anthropogenic climate change is the result of greenhouse gas accumulation in the atmosphere, which records the aggregation of billions of individual decisions. Here we consider a broad range of individual lifestyle choices and calculate their potential to reduce greenhouse gas emissions in developed countries, based on 148 scenarios from 39 sources. We recommend four widely applicable high-impact (i.e. low emissions) actions with the potential to contribute to systemic change and substantially reduce annual personal emissions: having one fewer child (an average for developed countries of 58.6 tonnes CO2-equivalent (tCO2e) emission reductions per year), living car-free (2.4 tCO2e saved per year), avoiding airplane travel (1.6 tCO2e saved per roundtrip transatlantic flight) and eating a plant-based diet (0.8 tCO2e saved per year). These actions have much greater potential to reduce emissions than commonly promoted strategies like comprehensive recycling (four times less effective than a plant-based diet) or changing household lightbulbs (eight times less). Though adolescents poised to establish lifelong patterns are an important target group for promoting high-impact actions, we find that ten high school science textbooks from Canada largely fail to mention these actions (they account for 4% of their recommended actions), instead focusing on incremental changes with much smaller potential emissions reductions. Government resources on climate change from the EU, USA, Canada, and Australia also focus recommendations on lower-impact actions. We conclude that there are opportunities to improve existing educational and communication structures to promote the most effective emission-reduction strategies and close this mitigation gap.
John Cook et al 2016 Environ. Res. Lett. 11 048002
The consensus that humans are causing recent global warming is shared by 90%–100% of publishing climate scientists according to six independent studies by co-authors of this paper. Those results are consistent with the 97% consensus reported by Cook et al (Environ. Res. Lett. 8 024024) based on 11 944 abstracts of research papers, of which 4014 took a position on the cause of recent global warming. A survey of authors of those papers (N = 2412 papers) also supported a 97% consensus. Tol (2016 Environ. Res. Lett. 11 048001) comes to a different conclusion using results from surveys of non-experts such as economic geologists and a self-selected group of those who reject the consensus. We demonstrate that this outcome is not unexpected because the level of consensus correlates with expertise in climate science. At one point, Tol also reduces the apparent consensus by assuming that abstracts that do not explicitly state the cause of global warming ('no position') represent non-endorsement, an approach that if applied elsewhere would reject consensus on well-established theories such as plate tectonics. We examine the available studies and conclude that the finding of 97% consensus in published climate research is robust and consistent with other surveys of climate scientists and peer-reviewed studies.
Md Abu Bakar Siddik et al 2021 Environ. Res. Lett. 16 064017
Much of the world's data are stored, managed, and distributed by data centers. Data centers require a tremendous amount of energy to operate, accounting for around 1.8% of electricity use in the United States. Large amounts of water are also required to operate data centers, both directly for liquid cooling and indirectly to produce electricity. For the first time, we calculate spatially-detailed carbon and water footprints of data centers operating within the United States, which is home to around one-quarter of all data center servers globally. Our bottom-up approach reveals one-fifth of data center servers direct water footprint comes from moderately to highly water stressed watersheds, while nearly half of servers are fully or partially powered by power plants located within water stressed regions. Approximately 0.5% of total US greenhouse gas emissions are attributed to data centers. We investigate tradeoffs and synergies between data center's water and energy utilization by strategically locating data centers in areas of the country that will minimize one or more environmental footprints. Our study quantifies the environmental implications behind our data creation and storage and shows a path to decrease the environmental footprint of our increasing digital footprint.
William F Lamb et al 2021 Environ. Res. Lett. 16 073005
Global greenhouse gas (GHG) emissions can be traced to five economic sectors: energy, industry, buildings, transport and AFOLU (agriculture, forestry and other land uses). In this topical review, we synthesise the literature to explain recent trends in global and regional emissions in each of these sectors. To contextualise our review, we present estimates of GHG emissions trends by sector from 1990 to 2018, describing the major sources of emissions growth, stability and decline across ten global regions. Overall, the literature and data emphasise that progress towards reducing GHG emissions has been limited. The prominent global pattern is a continuation of underlying drivers with few signs of emerging limits to demand, nor of a deep shift towards the delivery of low and zero carbon services across sectors. We observe a moderate decarbonisation of energy systems in Europe and North America, driven by fuel switching and the increasing penetration of renewables. By contrast, in rapidly industrialising regions, fossil-based energy systems have continuously expanded, only very recently slowing down in their growth. Strong demand for materials, floor area, energy services and travel have driven emissions growth in the industry, buildings and transport sectors, particularly in Eastern Asia, Southern Asia and South-East Asia. An expansion of agriculture into carbon-dense tropical forest areas has driven recent increases in AFOLU emissions in Latin America, South-East Asia and Africa. Identifying, understanding, and tackling the most persistent and climate-damaging trends across sectors is a fundamental concern for research and policy as humanity treads deeper into the Anthropocene.
Leroy J Walston et al 2024 Environ. Res. Lett. 19 014053
Global declines in insect populations have important implications for biodiversity and food security. To offset these declines, habitat restoration and enhancement in agricultural landscapes could mutually safeguard insect populations and their pollination services for crop production. The expansion of utility-scale solar energy development in agricultural landscapes presents an opportunity for the dual use of the land for energy production and biodiversity conservation through the establishment of grasses and forbs planted among and between the photovoltaic solar arrays ('solar-pollinator habitat'). We conducted a longitudinal field study across 5 years (2018–2022) to understand how insect communities responded to newly established habitat on solar energy facilities in agricultural landscapes by evaluating (1) temporal changes in flowering plant abundance and diversity; (2) temporal changes in insect abundance and diversity; and (3) the pollination services of solar-pollinator habitat by comparing pollinator visitation to agricultural fields near solar-pollinator habitat with other agricultural field locations. We found increases over time for all habitat and biodiversity metrics: floral rank, flowering plant species richness, insect group diversity, native bee abundance, and total insect abundance, with the most noticeable temporal increases in native bee abundance. We also found positive effects of proximity to solar-pollinator habitat on bee visitation to nearby soybean (Glycine max) fields. Bee visitation to soybean flowers adjacent to solar-pollinator habitat were comparable to bee visitation to soybeans adjacent to grassland areas enrolled in the Conservation Reserve Program, and greater than bee visitation to soybean field interior and roadside soybean flowers. Our observations highlight the relatively rapid (<4 year) insect community responses to grassland restoration activities and provide support for solar-pollinator habitat as a feasible conservation practice to safeguard biodiversity and increase food security in agricultural landscapes.
M Isabel Smith et al 2024 Environ. Res. Lett. 19 084041
Rapid warming in the Arctic threatens to destabilize mercury (Hg) deposits contained within soils in permafrost regions. Yet current estimates of the amount of Hg in permafrost vary by ∼4 times. Moreover, how Hg will be released to the environment as permafrost thaws remains poorly known, despite threats to water quality, human health, and the environment. Here we present new measurements of total mercury (THg) contents in discontinuous permafrost in the Yukon River Basin in Alaska. We collected riverbank and floodplain sediments from exposed banks and bars near the villages of Huslia and Beaver. Median THg contents were 49+13/−21 ng THg g sediment−1 and 39+16/−18 ng THg g sediment−1 for Huslia and Beaver, respectively (uncertainties as 15th and 85th percentiles). Corresponding THg:organic carbon ratios were 5.4+2.0/−2.4 Gg THg Pg C−1 and 4.2 +2.4/−2.9 Gg THg Pg C−1. To constrain floodplain THg stocks, we combined measured THg contents with floodplain stratigraphy. Trends of THg increasing with smaller sediment size and calculated stocks in the upper 1 m and 3 m are similar to those suggested for this region by prior pan-Arctic studies. We combined THg stocks and river migration rates derived from remote sensing to estimate particulate THg erosional and depositional fluxes as river channels migrate across the floodplain. Results show similar fluxes within uncertainty into the river from erosion at both sites (95+12/−47 kg THg yr−1 and 26+154/−13 kg THg yr−1 at Huslia and Beaver, respectively), but different fluxes out of the river via deposition in aggrading bars (60+40/−29 kg THg yr−1 and 10+5.3/−1.7 kg THg yr−1). Thus, a significant amount of THg is liberated from permafrost during bank erosion, while a variable but generally lesser portion is subsequently redeposited by migrating rivers.
Christine Shearer et al 2016 Environ. Res. Lett. 11 084011
Nearly 17% of people in an international survey said they believed the existence of a secret large-scale atmospheric program (SLAP) to be true or partly true. SLAP is commonly referred to as 'chemtrails' or 'covert geoengineering', and has led to a number of websites purported to show evidence of widespread chemical spraying linked to negative impacts on human health and the environment. To address these claims, we surveyed two groups of experts—atmospheric chemists with expertize in condensation trails and geochemists working on atmospheric deposition of dust and pollution—to scientifically evaluate for the first time the claims of SLAP theorists. Results show that 76 of the 77 scientists (98.7%) that took part in this study said they had not encountered evidence of a SLAP, and that the data cited as evidence could be explained through other factors, including well-understood physics and chemistry associated with aircraft contrails and atmospheric aerosols. Our goal is not to sway those already convinced that there is a secret, large-scale spraying program—who often reject counter-evidence as further proof of their theories—but rather to establish a source of objective science that can inform public discourse.
Jianxin Zeng et al 2024 Environ. Res. Lett. 19 114026
Compound hot-dry (CHD) and compound hot-wet (CHW) extremes have both intensified under global warming, posing exacerbated socio-economic threats compared to univariate extremes. This study presents a comprehensive assessment and comparison of the historical changes and driving factors behind CHD and CHW using observational data and climate model simulations. Findings indicate a notable surge in CHD and CHW occurrences, with CHW experiencing a higher increasing rate. Our investigation further reveals that anthropogenic climate change predominantly drives the increase in both types of compound extremes, especially for CHW. In contrast, land-atmosphere feedbacks have a limited impact on CHW at a global scale, but substantially contributes to the rise in CHD by reinforcing the negative precipitation-temperature coupling. This influence even surpasses that of anthropogenic climate change in specific regions. Understanding these variations and underlying causes is crucial for improving prediction accuracy and mitigating the impacts of compound extremes.
C R Fong et al 2024 Environ. Res. Lett. 19 114024
Mariculture will be important to meeting global seafood food demand in the coming decades. Yet, the threat of climate change—such as rising ocean temperatures—on mariculture performance remains uncertain. This is particularly true at small spatial scales relevant to most producers. Additionally, mariculture is often limited by regulations that impose restrictions on production, creating potential hurdles for anticipating and adapting to climate change. We focus on mariculture performance in the United States (U.S.), where state and federal policies and exposure to climate change vary substantially and likely interact. We map a current and future mariculture performance index by combining the first high resolution downscaled (0.083°) climate outputs for U.S. waters, species-specific physiological requirements, and policy restrictions. We find high current performance that will increase under warming oceans, with spatial variation that will amplify existing regional differences. Generally, performance will increase in the north and decrease in the south. While the permitting process is not intentionally climate-forward, permitted species outperformed taxon averages, yet state policies often limit production of seaweeds and finfishes, which perform well. Thus, we sit at a critical juncture where the U.S. could capitalize on its seemingly favorable environmental conditions through re-alignment of regulations to support portfolio diversification to include climate-resilient species.
Kentaro Takagi et al 2024 Environ. Res. Lett. 19 114022
Accurate evaluation of forest biomass distribution and its long-term change over wide areas is required for effective forest carbon management and prediction of landscape-scale forest dynamics. We evaluated a landscape-scale (225 km2) decadal forest carbon budget at a 1 ha spatial resolution in a cool-temperate forest, by repeating airborne laser observations 10 years apart and partitioning net forest biomass change (FBC) into growth and mortality. Using >10 000 samples, we revealed that naturally regenerated forests have large spatial heterogeneity in net biomass change, and 3/4 of the photosynthetically acquired carbon stock moved to necromass even without anthropogenic disturbances. Actual carbon residence time as living tree biomass was estimated by dividing biomass by growth or mortality rates. The residence time was 107 and 106 years, respectively with large spatial variation among stands (48 and 42 years, respectively, as the difference between 25 and 75 percentile), although studied forest stands have small variation in the forest functional type in a landscape-scale. The best predictors of subsequent decadal biomass changes were two forest structural factors, mean canopy height and canopy height variation in addition to one environmental factor, elevation. Considering the long lifetime of trees, these structural factors may be an indicator of forest soundness rather than a cause of forest growth or mortality. However, in any cases, these structural factors can be powerful predictors of subsequent FBC.
Hanwoong Kim et al 2024 Environ. Res. Lett. 19 114021
China has large, estimated potential for direct air carbon capture and storage (DACCS) but its deployment locations and impacts at the subnational scale remain unclear. This is largely because higher spatial resolution studies on carbon dioxide removal (CDR) in China have focused mainly on bioenergy with carbon capture and storage. This study uses a spatially detailed integrated energy-economy-climate model to evaluate DACCS for 31 provinces in China as the country pursues its goal of climate neutrality by 2060. We find that DACCS could expand China's negative emissions capacity, particularly under sustainability-minded limits on bioenergy supply that are informed by bottom-up studies. But providing low-carbon electricity for multiple GtCO2 yr−1 DACCS may require over 600 GW of additional wind and solar capacity nationwide and comprise up to 30% of electricity demand in China's northern provinces. Investment requirements for DACCS range from $330 to $530 billion by 2060 but could be repaid manyfold in the form of avoided mitigation costs, which DACCS deployment could reduce by up to $6 trillion over the same period. Enhanced efforts to lower residual CO2 emissions that must be offset with CDR under a net-zero paradigm reduce but do not eliminate the use of DACCS for mitigation. For decision-makers and the energy-economy models guiding them, our results highlight the value of expanding beyond the current reliance on biomass for negative emissions in China.
Qing Pei et al 2024 Environ. Res. Lett. 19 114025
A growing scholarship is focusing on the cost of social resilience to climate change in the past. Among different resilience strategies, migration could be effective for nomadic societies despite the potential consequences of conflicts and epidemics. Thus, this study utilizes historical records to statistically investigate the linkages among nomadic migrations, nomad–farmer conflicts, and epidemics under climate change and population pressure in imperial China (200 BCE–1840 CE) on the national and provincial scales. The current study will first attempt to empirically identify and analyze the cost of resilience to climate change mainly in the direction from nomadic societies to agrarian societies in historical China. In particular, we show the cost of nomadic migration passed in a chain mechanism as 'climate change → nomadic migration → nomad–farmer conflicts → epidemics.' Nomad–farmer conflicts were one direct effect of nomadic migration, while epidemics were an indirect one. Spatially, more provinces were affected under the direct effect than under the indirect effect. Furthermore, the first level of chain 'nomadic migration → nomad–farmer conflicts' covers more provinces than the second level 'nomad–farmer conflicts → epidemics'. These empirical results remind us to identify and avoid the cost of resilience as early as possible before the cost may transmit further in a chain manner. However, the provinces outside the concentrated nomad–farmer conflicts did not demonstrate significant linkages between conflicts and epidemics, which highlights the importance of peaceful cross-civilizational and inter-societal interactions against common challenges of climate change. This study with a cross-scale perspective in geography provides a theoretical implication to improve the current understanding on climate justice and have a practical value to avoid or minimize the cost of resilience.
H K Nesbitt et al 2024 Environ. Res. Lett. 19 113003
Social capital is frequently invoked as a reason for engaging in collaborative environmental governance. Yet we have a limited understanding of how collaborative environmental governance mobilizes different types of social capital and how the advantages and costs of social capital accrue for different groups of people. Explicit measures of social capital, such as through social network methods, will help build an understanding of how social capital facilitates collective processes and for whom. We reviewed highly cited articles in Web of Science and Scopus using 'social capital' as the search term to identify foundational and emergent social capital concepts. In the context of collaborative environmental governance, we operationalized these social capital concepts with network measures drawn from our expertise and highlighted existing empirical relationships between such network measures and collaborative outcomes. We identified two different perspectives on social capital—one based on social relations that could be readily operationalized with social network measures and the other based on actor characteristics that can further contextualize network data. Relational social capital concepts included social relations among actors; the collective social setting in which relations are embedded; and the advantages and costs that social capital confers to individuals and the collective. Social capital concepts based on actor characteristics included socio-cognitions (e.g. trust, norms, identification with a group, shared meanings) and community engagement (e.g. group membership, civic participation, volunteerism). Empirical evidence using social network approaches to measure social capital reveals patterns in relationship building that influence collaborative and other sustainability outcomes. Social network approaches described here may help define and quantify the social capital mobilized by collaborative governance. Additional research is necessary to track the social capital of collaboratives over time, link it to outcomes, and better understand the social justice implications of collaborative governance.
Z A Becvarik et al 2024 Environ. Res. Lett. 19 113001
Existing research suggests that a health-centred response to the climate crisis would support immediate and more ambitious action that minimises adverse health outcomes of climate change whilst providing additional co-benefits for population health. This review aimed to identify and assess literature that examines the health and wellbeing co-benefits of climate action in urban areas and to identify potential co-benefits that could be incorporated into policy or programme evaluation. We searched Scopus, PubMed and Web of Science, and screened titles, abstracts, and full-text. Peer-reviewed studies in English were included if they focused on health and wellbeing co-benefits of climate change adaptation and/or mitigation policies and programmes specific to urban areas. Our analysis found that all 39 studies in this review identified positive health and wellbeing co-benefits, with the majority focusing on transport policies and cross-sectoral mitigation and adaptation. All included studies employed a diverse array of modelling methodology, with multiple models and interdisciplinary approaches to evaluate co-benefits. Co-benefits ranged from reduced or avoided mortality and morbidity to social and economic health benefits. The degree of co-benefits differed according to the policies themselves; the policy sector; and vulnerability, demographic and/or geographic factors. Nine studies identified negative trade-offs of climate action. The review's findings add to existing literature in support of the value and importance of assessing the health and wellbeing co-benefits of climate action. The review also highlights the need for further identification and quantification of a comprehensive set of health and wellbeing co-benefits, improved data reporting and granularity, as well as research evaluating the impact of climate action that considers how vulnerability, demographic, geographic or other factors interact with policy implementation. This research is critical in informing the cost-effective prioritisation and coordination of climate policies that maximise human health benefits and promote health equity by minimising trade-offs for vulnerable groups.
Margot Sepp et al 2024 Environ. Res. Lett. 19 113002
More than half of the world's rivers experience occasional, seasonal, or permanent drying, and this may increase because of climate change. Drying, i.e. severe reduction in water flow even leading to streambed desiccation, can have a profound impact on the available aquatic habitat, biodiversity, and functions of rivers. Yet, to date, it is unclear whether similar drying events in comparable climate zones result in similar changes in ecosystem processes, such as river metabolism or greenhouse gas (GHG) emissions. Here, we synthesise the detected effects of drying on gross primary production (GPP) and ecosystem respiration (ER), as well as on the emissions of GHGs (CO2, CH4, and N2O) in rivers and streams. We examined the current available scientific literature detailing the impact of drying on these variables when measured either in the field or in the laboratory. We extracted data from 30 studies analysing GPP and ER responses, and data on GHG emissions from another 35 studies. Then, we conducted a meta-analysis to determine whether the magnitude and direction of the effects varied across the systems and climate zones studied, or according to the type (natural or human-induced) and severity of drying. In general, drying enhanced GPP (under low flows) and CH4 emissions, and decreased CO2 and N2O emissions. The hydrological phases throughout streambed drying (low water flow, isolated pools, or desiccation) had differential effects on metabolism and GHG emissions. The effects of drying were generally more severe when it induced desiccation, rather than just periods of low flow. Desiccation strongly reduced GPP, likely because of the die-off of algae, while its negative effect on ER was smaller. Greater decrease in GPP than in ER under desiccation would lead to increase in CO2 emissions; our results showed accordingly that desiccation increased CO2 emissions. Furthermore, the magnitude and direction of the effects varied depending on the study type. Experimental studies conducted in micro- and mesocosms demonstrated greater effects than field studies, thus the extrapolation of results from these to real conditions should be done with caution. Overall, the effects' direction was inconsistent across climate zones, except for the Mediterranean climate zone, where drying was showing a negative effect on both metabolism and GHG emissions. Our synthesis may contribute to identifying the worldwide trends and patterns of drying on riverine functions associated to global change impacts on river and stream ecosystems.
James N Galloway et al 2024 Environ. Res. Lett. 19 103003
As we face multiple environmental crises (e.g. climate change, nutrient pollution, freshwater scarcity), there is often a disconnect between an entity's activities and the pollution resulting from that activity. Footprint tools help address this disconnect. They are effective in educating people, institutions and communities on how their resource use results in environmental pollution and what we can do to moderate that pollution. These tools connect an entity's activities with the associated pollution. Footprint tools are also constantly evolving. As we better understand how to best estimate emissions—especially from sources further removed like those from the supply chain—the guidance and methods for calculating footprints is changing and improving. This paper reviews footprint tools for people, institutions and communities, with a focus on nitrogen footprint tools (NFTs). It also gives examples of how these tools have been applied to achieve pollution reductions. It concludes with an assessment of how nitrogen and multi-element footprint tools fit into the overall topic of environmental management and discusses their benefits and limitations.
Jose Castro et al 2024 Environ. Res. Lett. 19 103006
In contexts where conventional environmental monitoring has historically been limited, citizen science (CS) for monitoring efforts can be an effective approach for decentralized data generation that also raises scientific literacy and environmental awareness. To that end, the United Nations Environmental Program is considering CS as a mechanism for producing ambient water quality data to track progress on sustainable development goal (SDG) indicator 6.3.2: 'proportion of bodies of water with good ambient water quality'. However, the alignment of SDG 6.3.2 monitoring requirements with CS capacity and results in low- or middle-income countries has not been assessed. Through a systematic literature review of 49 journal publications, complemented by 15 key informant interviews, this article examines the methods and outputs of CS programs in resource-constrained settings. We explore the potential of these programs to contribute to tracking SDG 6.3.2. Using the CS impact assessment framework, we evaluate broader outcomes of CS programs across 5 domains: society, economy, environment, governance, and science and technology. Despite large variability in scope, CS programs were consistently found to generate useful data for national-level reporting on physicochemical and ecological parameters; however, data quality is a concern for CS measurement of microbiological parameters. The focus in literature to-date is predominantly on scientific data production which falls only within the 'science and technology' outcome domain. Societal, governance, economic, and environmental outcomes are infrequently evaluated. Of the studies reviewed in this article, 75% identified some form of pollution but only 22% of them reported follow-up actions such as reporting to authorities. While CS has important potential, work is still needed towards the 'formalization' of CS, particularly if intended for more vulnerable contexts.
Kim et al
The East Asian region is typically characterized by warm and humid conditions from late spring to summer. However, in recent decades, this region has experienced an increase in severe drying conditions, deviating from historical climatological patterns. This study investigated the precipitation-evaporation (P-E) trends across land and sea regions in East Asia (EA) during the extended summer season (April to September) from 1980 to 2022, and the key physical processes driving these trends through moisture budget decomposition and numerical experiments. The results reveal pronounced drying trends in southeastern China and the Yellow Sea and parts of the Korea Strait and Korean Peninsula over the past 43 years. The underlying physical processes driving these drying conditions differ between land and sea in EA. In southeastern China, the drying is driven by dynamic processes, particularly moisture divergence related to wind changes. This is linked to anomalous strengthening of descending motion due to the Indo-Pacific warm pool warming induced by both anthropogenic global warming and natural Pacific Decadal Oscillation-like sea surface temperature (SST) patterns. Conversely, drying in the Yellow Sea and adjacent areas is influenced by thermodynamic moisture advection. The altered humidity distribution due to global warming-induced SST patterns, which are higher over the Northwest Pacific marginal sea and lower in inland China, drives dry air transport from inland China to the Yellow Sea via background southwesterly wind. These findings enhance our understanding of the drying trend and their distinct processes in EA's land and sea areas during the extended summer.
Melo León et al
Overexploitation of groundwater for irrigation can ultimately threaten the viability of agriculture itself, because the falling groundwater levels become too deep to sustain the increasing costs of groundwater extraction, an economic limit is reached. In order to evaluate possible adaptation strategies to avoid or postpone reaching the economic limit, we developed the microeconomic heuristic model HELGA (Hydro-Economic Limits as a Global Analysis). HELGA considers the interaction of groundwater with irrigation at the farm level with a global scale application in mind. HELGA evaluates the development of the costs and revenue of groundwater-fed irrigated agriculture from the farmer's perspective. As long as the farm remains economically viable, the farmer can invest to access deeper groundwater, but in the long run the famer may have to adapt to keep farming profitable.
We tested HELGA in five locations within the conterminous USA. In most cases, recharge is large enough to save a farmer from reaching the economic limit. Where groundwater is overexploited, the increasing energy cost of groundwater pumping is one of the main drivers limiting groundwater use. Additionally, the increasing costs of the water infrastructure (i.e., deeper wells) is a crucial factor that explains where and when the economic limit is reached. If farmers change crops wisely or fallow part of their land, they are able to access groundwater longer and postpone the moment the economic limit is reached. Using HELGA, we show that proper and timely adaptation measures increases the profitable lifetime of groundwater and helps to conserve this resource for future generations.
Presberger et al
By importing goods whose production affects the environment abroad, wealthy countries are "offshoring" a large share of their total environmental footprint of consumption to less affluent societies. We argue that current efforts to mitigate this problem, which focus largely on informational policy instruments for global supply chains, could result in unintended side effects. The reason pertains to a potential tradeoff between a home bias in consumption and the geographic allocation of environmental impacts. We develop a theoretical argument on how consumers may respond when they prefer a domestically produced good but are made aware that this results in more environmental damage at home, compared to importing the same product from abroad. Based on choice experiments in Germany, Japan, and the United States, we observe that information provision can reduce consumer demand for environmentally harmful products, but also find some support for environmental NIMBYism when environmental and provenance information are combined. The key implication of this finding is that policymakers should address potentially unintended side-effects of more stringent informational requirements for global supply chains.
Blyth et al
Carbon monoxide (CO) is an atmospheric pollutant with a positive net warming effect on the climate. The magnitude of CO sources and the fraction of fossil vs biogenic sources are still uncertain and vary across emissions inventories. Measurements of radiocarbon (14C) in CO could potentially be used to investigate the sources of CO on a regional scale because fossil sources lack 14C and reduce the 14C/C ratio (Δ14C) of atmospheric CO more than biogenic sources. We use regional Lagrangian model simulations to investigate the utility of Δ14CO measurements for estimating the fossil fraction of CO emissions and evaluating bottom-up emissions estimates (United Kingdom Greenhouse Gas, UKGHG, and TNO Copernicus Atmosphere Monitoring Service, TNO) in London, UK. Due to the high Δ14CO in atmospheric CO from cosmogenic production, both fossil and biogenic CO emissions cause large reductions in Δ14CO regionally, with larger reductions for fossil than biogenic CO per ppb added. There is a strong seasonal variation in Δ14CO in background air and in the sensitivity of Δ14CO to fossil and biogenic emissions of CO. In the UK, the CO emissions estimate from TNO has a higher fraction from fossil fuels than UKGHG (72\% vs 67\%). This results in larger simulated decreases in Δ14C per ppb CO for TNO emissions. The simulated differences between UKGHG and TNO are likely to be easily detectable by current measurement precision, suggesting that Δ14CO measurements could be an effective tool to understand regional CO sources and assess bottom-up emissions estimates.
Schwab et al
Climate change in the northern circumpolar regions is rapidly thawing organic-rich permafrost soils, releasing substantial dissolved CO2 and CH4 into fluvial systems. This mobilization impacts local ecosystems and global climate feedback loops, playing a crucial role in the Arctic carbon cycle. Here, we analyze the stable carbon (δ13C) and radiocarbon (F14C) isotopic composition of dissolved CO2 and CH4 in the Sagavanirktok and Kuparuk River watersheds on the North Slope, Alaska. By examining spatial and seasonal variations in these isotopic signatures, we identify patterns of carbon release and transport along the river continuum. We find consistent CO2 isotopic signatures across the fluvial continuum, reflecting a mixture of geogenic and biogenic sources integrated throughout the watershed. Bayesian mixing models further demonstrate a systematic depletion in 13C and 14C signatures of dissolved CO2 sources from spring to fall, indicating increasing contributions of aged carbon as the active layer deepens seasonally. This seasonal deepening allows percolating groundwater to access deeper, older soil horizons, transporting CO2 produced by aerobic and anaerobic soil respiration to streams and rivers. In contrast, we observe no clear relationships between the 13C and 14C compositions of dissolved CH4 and landscape properties. Given the reduced solubility of CH4, which facilitates outgassing and limits its transport in aquatic systems, the isotopic signatures are likely indicative of localized contributions from streambeds, adjacent water saturated soils, and lake outflows. Our study demonstrates that dissolved greenhouse gases are sensitive indicators of the release of old carbon from thawing permafrost and serve as early warning signals for permafrost carbon feedback. It establishes a crucial baseline for understanding their role in regional carbon cycling and Arctic environmental change.