Anthropogenic Carbon Emissions Research Articles

Analysis of carbon emissions from land cover change during 2000 to 2020 in Shandong Province, China

Land cover change affects the carbon emissions of ecosystems in some way. The qualitative and quantitative understanding of carbon emissions from human activities (e.g., land cover change, industrial production, etc.) is highly significant for realizing the objective of carbon neutrality. Therefore, this paper used GlobeLand30 land cover maps, annual average normalised difference vegetation index (NDVI) data, annual average net ecosystem productivity (NEP) data and statistical yearbook data from 2000 to 2020 to explore the relationship between land cover change and carbon emissions. Specifically, it included land cover change, carbon storage changes influenced by land cover change, spatial and temporal analysis of carbon sources and sinks, land use intensity change and anthropogenic carbon emissions. The results of the study show that the main land cover changes in Shandong province during 2000–2020 was cultivated land conversion to artificial surfaces. Among them, the area of cultivated land converted to artificial surfaces from 2000 to 2010 was 4930.62 km2, and the proportion of cultivated land converted to artificial surfaces from 2010 to 2020 was as high as 78.35%. The total carbon stock of vegetation affected by land cover change decreased by 463.96 × 104 t and 193.50 × 104 t in 2000–2010 and 2010–2020 respectively. The spatial and temporal distribution of carbon sources and sinks differed more markedly from 2000 to 2020, and land use intensity changes in Shandong Province showed an upward trend. Of the total energy production, industry has the largest energy consumption, followed closely by total energy consumption in transportation, storage and postal services.

Changing ocean seasonal cycle escalates destructive marine heatwaves in a warming climate

Marine heatwaves (MHWs) can cause various adverse effects on marine ecosystems associated with complicated social ramifications. It has been well established that the gradually rising sea surface temperature (SST) due to anthropogenic carbon emission will cause an increase of the MHW duration and intensity. However, for species with strong adaptation capacity or mobility, MHW changes due to the altered SST variability under greenhouse warming are more crucial but so far remain poorly assessed. Under the high carbon emission scenario, we show that the cumulative duration (intensity) of MHWs, with the effect of secular SST increase excluded, is projected to be 60% (100%) higher by the end of this century than in the 1990s due to an amplified SST seasonal cycle. This increase becomes more evident for stronger MHWs, reaching up to 8 (30) folds for the extreme MHW category. The amplified SST seasonal cycle also causes pronounced seasonality of MHWs, making them more active in summer-autumn than winter-spring. Our results suggest that MHWs are likely to have increasingly devastating impacts on a wide range of marine species in the future without taking effective steps for carbon emission reduction.

Influence of Sugarcane Bagasse Ash and Silica Fume on the Mechanical and Durability Properties of Concrete.

Cement production is environmentally unsustainable due to the high anthropogenic carbon emissions produced. Supplementary cementitious materials (SCMs), derived from the by-products of different industries, have been deemed an effective way to reduce carbon emissions. The reduction in carbon emissions is achieved by lowering the clinker factor of cement, through a partial replacement with an SCM. Sugarcane Bagasse Ash (SCBA) is produced as an agricultural waste from the sugarcane industry and has gained a lot of attention for being a feasible and readily available pozzolanic material, underutilised as an SCM. This study evaluates alkali-activated sugarcane bagasse ash’s mechanical and durability performance, at varied contents, in binary blended cement concrete and ternary blended cement concrete containing silica fume (SF). Potassium Hydroxide (KOH), used as the alkali activator, is intended to enhance the reactivity of the ash, with the possibility of a high-volume SCBA content. The mechanical performance was investigated by compressive and split tensile strength tests, and durability performance was investigated using the Oxygen Permeability Index (OPI) test. In addition, a micro-CT porosity test was conducted to assess how the microstructure and porosity of the concrete affect the mechanical and durability performance. The results indicated that using SCBA in a ternary blend with SF can significantly improve the overall performance and create less porous concrete. At 30% SCBA and 10% SF replacement, the performance tests revealed the highest mechanical strength and the lowest permeability, outperforming the control concrete and the binary blended cement concrete containing only SCBA.

Regional sensitivity patterns of Arctic Ocean acidification revealed with machine learning

Ocean acidification is a consequence of the absorption of anthropogenic carbon emissions and it profoundly impacts marine life. Arctic regions are particularly vulnerable to rapid pH changes due to low ocean buffering capacities and high stratification. Here, an unsupervised machine learning methodology is applied to simulations of surface Arctic acidification from two state-of-the-art coupled climate models. We identify four sub-regions whose boundaries are influenced by present-day and projected sea ice patterns. The regional boundaries are consistent between the models and across lower (SSP2-4.5) and higher (SSP5-8.5) carbon emissions scenarios. Stronger trends toward corrosive surface waters in the central Arctic Ocean are driven by early summer warming in regions of annual ice cover and late summer freshening in regions of perennial ice cover. Sea surface salinity and total alkalinity reductions dominate the Arctic pH changes, highlighting the importance of objective sub-regional identification and subsequent analysis of surface water mass properties.

GISD30: global 30 m impervious-surface dynamic dataset from 1985 to 2020 using time-series Landsat imagery on the Google Earth Engine platform

Abstract. Accurately mapping impervious-surface dynamics has great scientific significance and application value for research on urban sustainable development, the assessment of anthropogenic carbon emissions and global ecological-environment modeling. In this study, a novel and automatic method of combining the advantages of spectral-generalization and automatic-sample-extraction strategies was proposed, and then an accurate global 30 m impervious-surface dynamic dataset (GISD30) for 1985 to 2020 was produced using time-series Landsat imagery on the Google Earth Engine cloud computing platform. Firstly, the global training samples and corresponding reflectance spectra were automatically derived from prior global 30 m land-cover products after employing the multitemporal compositing method and relative radiometric normalization. Then, spatiotemporal adaptive classification models, trained with the migrated reflectance spectra of impervious surfaces from 2020 and transferred pervious-surface samples in each epoch for every 5∘×5∘ geographical tile, were applied to map the impervious surface in each period. Furthermore, a spatiotemporal-consistency correction method was presented to minimize the effects of independent classification errors and improve the spatiotemporal consistency of impervious-surface dynamics. Our global 30 m impervious-surface dynamic model achieved an overall accuracy of 90.1 % and a kappa coefficient of 0.865 using 23 322 global time-series validation samples. Cross-comparisons with five existing global 30 m impervious-surface products further indicated that our GISD30 dynamic product achieved the best performance in capturing the spatial distributions and spatiotemporal dynamics of impervious surfaces in various impervious landscapes. The statistical results indicated that the global impervious surface has doubled in the past 35 years, from 5.116×105 km2 in 1985 to 10.871×105 km2 in 2020, and Asia saw the largest increase in impervious surface area compared to other continents, with a total increase of 2.946×105 km2. Therefore, it was concluded that our global 30 m impervious-surface dynamic dataset is an accurate and promising product and could provide vital support in monitoring regional or global urbanization as well as in related applications. The global 30 m impervious-surface dynamic dataset from 1985 to 2020 generated in this paper is free to access at https://doi.org/10.5281/zenodo.5220816 (Liu et al., 2021b).

Human metabolic emissions of carbon dioxide and methane and their implications for carbon emissions

Carbon dioxide (CO2) and methane (CH4) are important greenhouse gases in the atmosphere and have large impacts on Earth's radiative forcing and climate. Their natural and anthropogenic emissions have often been in focus, while the role of human metabolic emissions has received less attention. In this study, exhaled, dermal and whole-body CO2 and CH4 emission rates from a total of 20 volunteers were quantified under various controlled environmental conditions in a climate chamber. The whole-body CO2 emissions increased with temperature. Individual differences were the most important factor for the whole-body CH4 emissions. Dermal emissions of CO2 and CH4 only contributed ~3.5% and ~5.5% to the whole-body emissions, respectively. Breath measurements conducted on 24 volunteers in a companion study identified one third of the volunteers as CH4 producers (exhaled CH4 exceeded 1 ppm above ambient level). The exhaled CH4 emission rate of these CH4 producers (4.03 ± 0.71 mg/h/person, mean ± one standard deviation) was ten times higher than that of the rest of the volunteers (non-CH4 producers; 0.41 ± 0.45 mg/h/person). With increasing global population and the expected large reduction in global anthropogenic carbon emissions in the next decades, metabolic emissions of CH4 (although not CO2) from humans may play an increasing role in regional and global carbon budgets.

Projected reversal of oceanic stable carbon isotope ratio depth gradient with continued anthropogenic carbon emissions

Paleoceanographic records suggest that the present-day vertical gradient in the stable carbon isotopic composition (δ13C) of dissolved inorganic carbon in the ocean was reversed during the Paleocene-Eocene Thermal Maximum, an early period of relatively rapid release of carbon into the climate system. Here we present simulations from an observationally constrained ocean model under various greenhouse gas emissions scenarios. We project a decrease in the globally averaged δ13C of dissolved inorganic carbon in the surface ocean of between −1.8 to −6.3 ‰ by 2100. This reduction is driven by oceanic absorption of anthropogenic carbon dioxide, which is depleted in carbon-13. Our findings suggest an elimination or reversal of the natural vertical gradient in the δ13C of dissolved inorganic carbon by 2100 unless anthropogenic carbon emissions are reduced soon. We conclude that the Paleocene-Eocene Thermal Maximum is a geologic analogue of future global carbon cycle perturbations under continued rapid anthropogenic carbon emissions.

Prospects for low-carbon design theory of concrete structures

<p indent="0mm">Industrial civilization causes huge carbon emissions, accelerates climate change, and hinders the sustainable development of human society. The construction industry causes about 40% of annual global anthropogenic carbon emissions, within which the massive construction of concrete structures alone accounts for more than 10% of the global emissions. China’s national goals for carbon peaking, neutrality, and the low-carbon development consensus call for the low-carbon design theory of concrete structures in the construction industry. Starting from the scientific issues with the concrete structure-environment symbiotic system, this paper clarifies the indicators, design methods and tuning means of low-carbon structural design, aiming to lay a foundation and provide suggestions for the development of low-carbon design, and promote the sustainable development of concrete industry. By briefly reviewing the history of the concrete industry, we illustrate the trend of low-carbon transitions, for which it is urgently needed to shift the perspective of structural design from only centering on human needs to meeting the sustainable needs of the integrated system of concrete structures and environments. Based on the characteristics of carbon emissions and uptake of concrete structures, the significance of regulating concrete structures’ net embodied carbon emissions for climate change mitigation is clarified. Further, to cope with climate change, we put forward the scientific issues and design requirements for the concrete structure-environment symbiotic system. To facilitate the sustainable development of the concrete structure-environment symbiotic system, we focus the low-carbon design method on the quantitative characterization of structure-environment dynamic coupling. The structural sustainability indicator is established to simultaneously reflect the structural reliability and carbon emission level of concrete structures. Further, we sort out relevant evaluation and design methods into the evolution of low-carbon design from the structural reliability design considering sustainability to the sustainability design characterized by a bidirectional perspective, which means the design methodology has developed from the reliability guarantee of qualitative low-carbon strategies facing climate change to quantitative carbon emission target guarantee in the form of conditional probability control, which ensures both low-carbon emissions and reliable service performance during the life cycle of concrete structures under climate change. Further, in order to assist the low-carbon design regulation, we put forward the carbon emission-based 3R^+C principles, i.e., carbon reduction, carbon reuse, and carbon recycling, to construct a low-carbon design technology system with superimposable carbon emission reduction benefits among categories. Typical low-carbon technologies for concrete structures are classified following the three principles according to their main emission reduction advantages, i.e., embodied carbon reduction in material production, embodied carbon allocation by construction mode transition, and carbon uptake with a developed end-of-life management system, and their emission reduction potential and promotion prospects are explored. A lot of future work is needed for the innovative development and promotion of low-carbon design of concrete structures, which includes clarifying the carbon emission benchmarks and goals for the concrete industry, strengthening the identification and management of failure risks and possible failure consequences under climate change, enriching and improving available low-carbon design technologies, and developing codes and software for integrated low-carbon design.

Rock Physics-Based Data Assimilation of Integrated Continuous Active-Source Seismic and Pressure Monitoring Data during Geological Carbon Storage

Summary There has been substantial controversy concerning the role of geological carbon storage (GCS) in sequestering anthropogenic carbon emissions to mitigate climate change and global warming. Arguments center on the inability to monitor a geological storage site precisely and continuously, especially highlighting the associated costs and spatiotemporal trade-offs when using conventional subsurface monitoring techniques (well logs, core samples, chemical tracers, and 4D seismics). Active surveillance of GCS sites is essential for managing and mitigating potential leaks but is also required by regulation. With the goal of enhancing the monitoring capability at GCS sites, we present a rock physics-based joint data assimilation model to study a popular GCS site at Cranfield, Mississippi, USA. Synthetic continuous active-source seismic monitoring (CASSM) data (in the form of Vp and Qp measurements) and wellbore pressure monitoring data are assimilated with an ensemble of reservoir realizations to monitor gas saturation and reservoir pressure changes over a period of 100 years. Synthetic seismic attributes are generated using rock physics models (RPMs) and wellbore pressure monitoring data are extracted from the ground truth. Two assimilation methods, ensemble Kalman filter (EnKF) and ensemble Kalman smoother (EnKS), are tested in an observation system simulation experiment (OSSE) environment to assess the prediction accuracy of the individual and composite observation systems. The joint monitoring system achieves more accurate estimates of gas saturation and pressure, across the time span from start of injection to end of forecast, as compared to a single type of monitoring tool and irrespective of data assimilation algorithm choice. These results indicate that jointly assimilated data from two types of sensors (in this case, crosswell seismic and downhole pressure) may lead to a more risk-reducing monitoring design. One would expect that more data, vis-à-vis inclusion of a new sensor type, will improve the accuracy of any GCS monitoring system. However, from a practical standpoint, one important question is whether such a gain in accuracy is worth the additional cost associated with the new sensor. This paper focuses on quantifying the gain in accuracy, such that a practitioner can answer this question.

Isotopic filtering reveals high sensitivity of planktic calcifiers to Paleocene–Eocene thermal maximum warming and acidification

Ocean warming and acidification driven by anthropogenic carbon emissions pose an existential threat to marine calcifying communities. A similar perturbation to global carbon cycling and ocean chemistry occurred ∼56 Ma during the Paleocene-Eocene thermal maximum (PETM), but microfossil records of the marine biotic response are distorted by sediment mixing. Here, we use the carbon isotope excursion marking the PETM to distinguish planktic foraminifer shells calcified during the PETM from those calcified prior to the event and then isotopically filter anachronous specimens from the PETM microfossil assemblages. We find that nearly one-half of foraminifer shells in a deep-sea PETM record from the central Pacific (Ocean Drilling Program Site 865) are reworked contaminants. Contrary to previous interpretations, corrected assemblages reveal a transient but significant decrease in tropical planktic foraminifer diversity at this open-ocean site during the PETM. The decrease in local diversity was caused by extirpation of shallow- and deep-dwelling taxa as they underwent extratropical migrations in response to heat stress, with one prominent lineage showing signs of impaired calcification possibly due to ocean acidification. An absence of subbotinids in the corrected assemblages suggests that ocean deoxygenation may have rendered thermocline depths uninhabitable for some deeper-dwelling taxa. Latitudinal range shifts provided a rapid-response survival mechanism for tropical planktic foraminifers during the PETM, but the rapidity of ocean warming and acidification projected for the coming centuries will likely strain the adaptability of these resilient calcifiers.

Grassland rehabilitation significantly increases soil carbon stocks by reducing net soil CO2 emissions

AbstractRestoration of degraded grasslands through improved management is among the possible sustainable solutions to compensate for anthropogenic soil carbon (C) emissions. While several studies have shown a positive effect of rehabilitation on soil C, the impact on soil CO2 emissions is still uncertain. Therefore, this study aimed at quantifying the impact of grassland rehabilitation on soil CO2 emissions in a degraded grassland, South Africa. Commonly used rehabilitation practices were considered, that is rotational grazing (RG), livestock exclosure with fertilizer application (EF) and annual burning (AB), all being compared with traditional free grazing (FG). A total of 2880 in situ measurements of CO2 emissions were performed over 2.5 years under field conditions simultaneously with aboveground biomass, soil temperature, water content and soil organic C (SOC) to understand the changes in C fluxes. The RG performed the best under degraded grasslands by decreasing net CO2 emissions (per g of C) by 17% compared to FG, while EF increased emissions by 76% and AB had similar emissions to FG. The lower net emission under RG is associated with an increase in SOC stocks by 50% and aboveground biomass by 93%, after three years of implementation. Soil CO2 emissions were correlated positively to aboveground biomass and topsoil temperature (r = 0.91 and 0.60, respectively), implying a high effect of grass cover on soil microclimate and microbial activity. These results suggested RG as a potential cost‐effective nature‐based soil management strategy to increase SOC stocks into degraded grassland. However, long‐term trials replicated in different environments are still required.

Australia's Experience of Combining Building Energy Standards and Disclosure Regulation

Multiple market failures have historically delivered housing that is environmentally and economically sub-optimal. Minimum energy standards are a popular policy tool for lowering energy use and anthropogenic carbon emissions in the built environment, but evidence shows they fail to drive performance beyond that minimum. Mandating the disclosure of energy performance on sale or lease of property has been introduced in some jurisdictions to transform the building stock and encourage energy and carbon saving improvements. These policy instruments address different market failures and have the potential to act as complementary regulation, but to date there has been little evidence that the combination may deliver greater benefits than each individual policy measure. The analysis of 342,674 housing energy assessments in Australia from May 2016–June 2021 highlights the impact of complementary vs. single policy instruments. We find that the building regulatory process alone delivers certainty regarding minimum performance, but when matched with disclosure regulation, the market is pulled slightly toward higher performance outcomes than for where building regulations alone are used. While only a small improvement in performance, the data supports the power of complementary regulation for long-life housing assets, similar to the benefits found for shorter-life assets such as household appliances; in essence creating both a carrot and a stick for consumers and the wider market. The data from Australia presented in this paper suggests that the use of complementary regulation may deliver improved environmental and economic outcomes and could help jurisdictions governing a transition to more sustainable housing as part of the wider transition to sustainable cities.

Study on the Influential Factors of CO2 Storage in Low Permeability Reservoir

As the demands of tight-oil Enhanced Oil Recovery (EOR) and the controlling of anthropogenic carbon emission have become global challenges, Carbon Capture Utilization and Sequestration (CCUS) has been recognized as an effective solution to resolve both needs. However, the influential factors of carbon dioxide (CO2) geological storage in low permeability reservoirs have not been fully studied. Based on core samples from the Huang-3 area of the Ordos Basin, the feasibility and influential factors of geological CO2 sequestration in the Huang-3 area are analyzed through caprock breakthrough tests and a CO2 storage factor experiment. The results indicate that capillary trapping is the key mechanism of the sealing effect by the caprock. With the increase of caprock permeability, the breakthrough pressure and pressure difference decreased rapidly. A good exponential relationship between caprock breakthrough pressure and permeability can be summarized. The minimum breakthrough pressure of CO2 in the caprock of the Huang-3 area is 22 MPa, and the breakthrough pressure gradient is greater than 100 MPa/m. Huang-3 area is suitable for the geological sequestration of CO2, and the risk of CO2 breakthrough in the caprock is small. At the same storage percentage, the recovery factor of crude oil in larger permeability core is higher, and the storage percentage decreases with the increase of recovery factor. It turned out that a low permeability reservoir is easier to store CO2, and the storage percentage of carbon dioxide in the miscible phase is greater than that in the immiscible phase. This study can provide empirical reference for caprock selection and safety evaluation of CO2 geological storage in low permeability reservoirs within Ordos Basin.

Green materials for carbon storage in depleted oilfields: An experimental study

The incessant rise in global temperature due to the large increase in anthropogenic carbon emissions over the past century threaten to undo gains made by human civilization and it has become essential that techniques to reduce atmospheric carbon be explored. For this, carbon-negative technologies like carbon geo-storage hold high vitality for industrial applications. In carbon geo-storage, captured CO2 is injected into the subsurface formations like depleted oilfields. However, the injected CO2 tends to undergo viscous fingering, bypassing small pore throats and consequently, the volumetric storage efficiency is reduced. Thus, there is a need for new mobility control agents which not only improve the volumetric storage efficiency of CO2 but also help alter rock surface for longer CO2 retention. Thus, in this study, the use of a novel green surfactant (S) has been explored in conjunction with natural polymers (P), guar gum and xanthan gum for CO2 mobility control. The composition of the SP solution was finalized via contact angle studies in presence of CO2. Following this, CO2 injection at varying flow rates (30–90 ml/h) was investigated in sand-packs of porosity 27–31% and permeability ≈682–812 mD which was saturated with a residual reservoir brine of 4 wt% NaCl. The role of the green SP solution was validated by injecting a slug of 0.3 pore volume (PV) before CO2 injection and the time to breakthrough for gas, the liquid return before breakthrough and the pressure drop profiles were carefully analyzed. It was found that the inclusion of green surfactant improved carbon retention by a factor of 3–4.5 (in the presence of other polymers) which was also demonstrated by an increase in areal coverage inside the sand-pack (as established from the pressure drop studies). Thus, the use of a green SP solution is proposed as a mobility control agent for carbon storage in depleted oilfields.

Evaluation of anthropogenic emissions of black carbon from East Asia in six inventories: constraints from model simulations and surface observations on Fukue Island, Japan

This study evaluates anthropogenic black carbon emissions from East Asia for five global inventories and one regional inventory using a chemical transport model and observations at Fukue Island in Japan.

Carbon footprints of the Indian AFOLU (Agriculture, Forestry, and Other Land Use) sector: a review

Stabilizing greenhouse gas (GHG) emissions from croplands as agricultural demand grows is a critical climate change mitigation strategy. Depending on management, the Agriculture, Forestry, and Other Land Use (AFOLU) sector can be both a source as well as a net sink for carbon. Currently, it contributes 25% of the global anthropogenic carbon emissions. Although India’s emissions from this sector are around 8% of the total national GHG emissions, it can contribute significantly to the country’s aspirations of reaching net-zero emissions by 2070. In this review, we explain the carbon footprints of the AFOLU sector in India, focusing on enteric fermentation, fertilizer and manure management, rice paddies, burning of crop residues, forest fires, shifting cultivation, and food wastage. Furthermore, using the standard autoregressive integrated moving average method, we project India’s AFOLU sector emission routes for 2070 under four scenarios: business as usual (BAU) and three emission reduction levels, viz., 10%, 20%, and 40% below BAU. The article focuses on how the AFOLU sector can be leveraged proactively to reach the net-zero emission goals. Increasing forest cover, agroforestry, and other tree-based land-use systems; improving soil health through soil management, better crop residue, and livestock feed management; emission avoidance from rice ecosystems; and reducing food waste are all important strategies for lowering India’s AFOLU sector carbon footprints.

Modeling the Carbon Cycle Dynamics and the Greenhouse Effect

A carbon cycle model is proposed that predicts changes in the atmospheric CO2 concentration, and provides a global temperature estimate from an empirical correlation of the two variables. The model is validated by simulating the anthropogenic carbon emissions and deforestation since the industrial revolution, and comparing the predicted and measured atmospheric CO2 concentration and global temperature data. The temperature data are also compared with those predicted by a greenhouse effect model based on the effective emission temperature hypothesis. The result suggests that radiative forcing by CO2 alone can account for only about half of the measured global warming. The model requires further elaboration for the other half, in order to be applicable to simulation of potential climate control.

High CO2 Expands Where Plants Can Grow in CESM‐CLM4‐CNDV

AbstractAs anthropogenic carbon emissions continue, it is important to predict how vegetation will change due to the warming climate, increasing atmospheric CO2, and changing precipitation patterns. Some projections show decreases in vegetation either regionally in the tropics (e.g., Falloon et al., 2012; Port et al., 2012) or globally (e.g., Bastin et al., 2019) due to high temperatures and drying, and there is large uncertainty surrounding the response of global vegetation to climate change (Arora et al., 2020; Friedlingstein et al., 2006; Walker et al., 2020). Here we use simulations with the NCAR Community Earth System Model (CESM) with dynamic vegetation to explore how increasing CO2 may affect vegetation and, through feedbacks, the climate. We find that globally, warming only decreases vegetation, but when we include the effects of CO2 on plant physiology, vegetated area increases by ∼23% relative to the preindustrial simulation. This greening occurs even without significant increases in precipitation, as high CO2 increases plant water use efficiency, allowing for more vegetation in arid and hot regions. Our results show that CO2‐induced vegetation changes affect climate by amplifying high latitude warming, cooling some areas of the tropics, and shifting global precipitation patterns. Our results highlight the importance of including climate‐vegetation feedbacks in Earth system modeling.

Ecological Land Protection or Carbon Emission Reduction? Comparing the Value Neutrality of Mainstream Policy Responses to Climate Change

Improving the quality of forest, water, farmland, and other types of land use with outstanding ecosystem optimization, restoration functions (ecological lands) and reducing anthropogenic carbon emissions are recognized as the two main approaches of current mainstream climate change policies. The paper aims to evaluate and compare the value neutrality within these two main types of policy responses to climate change. To do that, a case study was conducted at the Yangtze River Economic Belt, China. We first summarized the implementation status of all climate change policies in the study area and collected data related to climate and economy at the policy pilot sites. Next, the coupling relationship between climate and socio-economic conditions at policy pilot sites was calculated by the Tapio model. Finally, we constructed dummy variables that reflected the status of policy implementation, to estimate the value neutrality of mainstream climate change policies and their impact on the coupling relationship by DID models. The results showed that the proportion of policies related to ecological lands that significantly improved the coupling degree between climate and socio-economic conditions of the pilot sites is more than that of carbon emission-related ones. Moreover, the average coupling degree between climate and socio-economic conditions of the pilot sites of ecological land policies was significantly increased by 3.99 units after policy implementation, which is 27.8% higher than that of carbon emission reduction policies. Generally, the two main findings directly evidenced that the climate change policies aimed at improving the area and quality of ecological lands were more conducive to the coupling development of the climate–economy nexus than the policies focusing on restricting carbon emissions, which provides important enlightenment for the establishment of relevant environmental policies around the world.

Biogeochemical extremes and compound events in the ocean.

The ocean is warming, losing oxygen and being acidified, primarily as a result of anthropogenic carbon emissions. With ocean warming, acidification and deoxygenation projected to increase for decades, extreme events, such as marine heatwaves, will intensify, occur more often, persist for longer periods of time and extend over larger regions. Nevertheless, our understanding of oceanic extreme events that are associated with warming, low oxygen concentrations or high acidity, as well as their impacts on marine ecosystems, remains limited. Compound events-that is, multiple extreme events that occur simultaneously or in close sequence-are of particular concern, as their individual effects may interact synergistically. Here we assess patterns and trends in open ocean extremes based on the existing literature as well as global and regional model simulations. Furthermore, we discuss the potential impacts of individual and compound extremes on marine organisms and ecosystems. We propose a pathway to improve the understanding of extreme events and the capacity of marine life to respond to them. The conditions exhibited by present extreme events may be a harbinger of what may become normal in the future. As a consequence, pursuing this research effort may also help us to better understand the responses of marine organisms and ecosystems to future climate change.