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Robust mitigation options will play significant role in achieving the target of limiting global change to below 1.5 °C above pre-industrial levels by 2100. To support cooperation for mitigation development, we establish a real options-based model to evaluate the rational decisions of exercising the abandon option for carbon capture and storage-enhanced oil recovery (CCS-EOR) projects under oil market and geological uncertainties. Three possible cooperative mechanisms (fixed carbon dioxide (CO2) price, oil-indexed CO2 price, and joint venture contracts) among CO2-EOR stakeholders are evaluated. The results show that the conflicts in profit maximization targets for different stakeholders in cooperative mitigation are to a great extent unable to be avoided. A joint venture business model is preferred in cooperative mitigation as it can effectively weaken such conflicts. And it is more reasonable to provide incentives to the downstream of the CO2-EOR chain than compensating the adoption cost of carbon capture technologies in the upstream. From a global perspective, the inefficient cooperation can be a main barrier that hinders the development of deep-cutting options. Global mitigation strategies should not only focus on promoting technology progress but also the design of innovative business models to balance the benefits among stakeholders. A joint venture business model is recommended in both the developed and developing countries for seizing the early mitigation opportunities.

This study highlights how Chinese economic development detrimentally impacted water quality in recent decades and how this has been improved by enormous investment in environmental remediation funded by the Chinese government. To our knowledge, this study is the first to describe the variability of surface water quality in inland waters in China, the affecting drivers behind the changes, and how the government-financed conservation actions have impacted water quality. Water quality was found to be poorest in the North and the Northeast China Plain where there is greater coverage of developed land (cities + cropland), a higher gross domestic product (GDP), and higher population density. There are significant positive relationships between the concentration of the annual mean chemical oxygen demand (COD) and the percentage of developed land use (cities + cropland), GDP, and population density in the individual watersheds (p < 0.001). During the past decade, following Chinese government-financed investments in environmental restoration and reforestation, the water quality of Chinese inland waters has improved markedly, which is particularly evident from the significant and exponentially decreasing GDP-normalized COD and ammonium (NH4+-N) concentrations. It is evident that the increasing GDP in China over the past decade did not occur at the continued expense of its inland water ecosystems. This offers hope for the future, also for other industrializing countries, that with appropriate environmental investments a high GDP can be reached and maintained, while simultaneously preserving inland aquatic ecosystems, particularly through management of sewage discharge.

Low carbon transformation plays an important role in promoting the energy production and consumption revolution. Currently, the power sector of China still faces a series of challenges, such as the overcapacity of coal-fired power, the renewable energy consumption, the new constraints of carbon-emissions, and fragmented power planning. This study develops a multi-objective optimization model to predict the future trend of China power structure by 2035. The key factors such as network, power, load and storage are taken into account. Besides, the technical feasibility, economic rationality and social acceptable constraints are also fully considered. Through planning and optimization, the premise of low carbon transformation is to ensure the continuity of existing policies for removing inefficient assets, and the core is to develop and utilize non-fossil energy on a large scale. Specifically, the capacity of coal-fired power will be attained in the peak in 2025, and the factor will also transfer from main power supplier to main power and energy supplier. Before 2025, the clean replacement of incremental power installation will be completed. In 2035, 92% of new investment comes from non-fossil energy. The economy and competitiveness of wind power and PV (Photovoltaic) power generation are continuously increasing. By 2020, the coal-fired power and the wind power in eastern of China will be parity firstly. In 2025, the cost of PV and wind power will be the same. Furthermore, the evaluation dimension of modern power system with clean, low-carbon, safety and high efficiency are innovatively constructed, and the index system target of 2035 is quantitatively analyzed and prospected.

Carbonaceous aerosols (CAs) scatter and absorb incident solar radiation in the atmosphere, thereby influencing the regional climate and hydrological cycle, particularly in the Third Pole (TP). Here, we present the characteristics of CAs at 19 observation stations from the Atmospheric Pollution and Cryospheric Change network to obtain a deep understanding of pollutant status in the TP. The organic carbon (OC) and elemental carbon (EC) concentrations decreased noticeably inwards from outside to inland of the TP, consistent with their emission load and also affected by transport process and meteorological condition. Urban areas, such as Kathmandu, Karachi, and Mardan, exhibited extremely high OC and EC concentrations, with low and high values occurring in the monsoon and non-monsoon seasons, respectively. However, remote regions inland the TP (e.g., Nam Co and Ngari) demonstrated much lower OC and EC concentrations. Different seasonal variations were observed between the southern and northern parts of the TP, suggesting differences in the patterns of pollutant sources and in distance from the sources between the two regions. In addition to the influence of long-range transported pollutants from the Indo-Gangetic Plain (IGP), the TP was affected by local emissions (e.g., biomass burning). The OC/EC ratio also suggested that biomass burning was prevalent in the center TP, whereas the marginal sites (e.g., Jomsom, Dhunche, and Laohugou) were affected by fossil fuel combustion from the up-wind regions. The mass absorption cross-section of EC (MACEC) at 632 nm ranged from 6.56 to 14.7 m2 g-1, with an increasing trend from outside to inland of the TP. Urban areas had low MACEC values because such regions were mainly affected by local fresh emissions. In addition, large amount of brown carbon can decrease the MACEC values in cities of South Asia. Remote sites had high MACEC values because of the coating enhancement of aerosols. Influenced by emission, transport process, and weather condition, the CA concentrations and MACEC presented decreasing and increasing trends, respectively, from outside to inland of the TP.

Abstract The transport sector has become an important source of urban greenhouse gas (GHG) and air pollutant emissions, with the continuous growth of transportation demand. The co-benefits of reducing GHG and air pollutant emissions in the transport sector are receiving more and more attention. Taking Guangzhou as the case study city, this study quantitatively analyzed the co-benefits of reducing CO2 and air pollutant emissions under the sustainable scenario in the transport sector by developing a quantitative analysis model based on the Long-range Energy Alternatives Planning (LEAP) framework. The co-benefits quantitative parameter and the co-benefits radar chart analysis method are used to identify and evaluate the generated co-benefits, and then the co-benefits generated by implementing the sustainable measures are discussed. The results show that adjusting transport modes and increasing the application of electricity are the two most effective measures for achieving the co-benefits of reducing CO2 and air pollutant emissions in the Guangzhou transport sector. Thus, these two measures are highly preferential for mitigating CO2 and air pollutant emissions. In addition, increasing the application of biofuel and hydrogen energy also has good co-benefits. However, increasing the application of Liquefied Natural Gas (LNG) has poor co-benefits. Promoting the utilization of LNG intercity buses, trucks, and cargo ships will lead to emission increases of CO and HC compared to the current policy scenario, and small emission reductions of CO2 and other air pollutants. Therefore, to promote the utilization of LNG vehicles and ships, it is necessary to cooperate with the use of air pollutant end removal devices and high-pressure direct injection (HPDI) gas engines.

Ecosystem water use efficiency (EWUE) is a popular issue in the comprehensive study of climate change, ecology, and hydrology. Currently, views on the response of EWUE to temperature, precipitation, and drought remain controversial. Based on ecosystem net primary productivity (NPP) and evapotranspiration (ET) datasets, both of which were retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) using the Carnegie Ames Stanford approach (CASA) and surface energy balance algorithms for land (SEBAL) models, respectively, this study comprehensively examined the relationship between EWUE and temperature, precipitation, and drought in the Tianshan Mountains of Central Asia. The results showed that EWUE had an obvious temporal change trend in the Tianshan Mountains. The EWUEs of all vegetation types presented an increasing trend in spring and a decreasing trend in autumn. These results led to a phase shift in the annual cycle of EWUE over the years. Compared with 2000 to 2003, from 2012 to 2016, the annual EWUE cycle had advanced by 32 days. Precipitation generally had a negative effect on EWUE, while temperature had an obvious positive effect on EWUE. The EWUE responses to drought for the different vegetation types showed a variety of change trends. With the increase in drought stress, EWUE not only showed a simple upward or downward trend but also showed an upward trend followed by a downward trend or a downward trend followed by an upward trend. EWUE is more sensitive to changing environments than NPP or ET and is more suitable for analyzing ecosystem responses to global change.

Improving energy efficiency is regarded as a key path to tackling global warming and achieving the Sustainable Development Goals (SDGs). In 2020, the energy consumption of the world's ten major energy-consuming countries accounted for 66.8% of the global total. This paper applied data envelopment analysis (DEA) to calculate these ten major energy-consuming countries' total-factor energy efficiency (TFEE) at national and sectoral levels from 2001-2020, and explored the influencing factors of total-factor energy efficiency with the Tobit regression model. The results showed significant difference in the ten countries' energy efficiency. The United States and Germany topped the list for total-factor energy efficiency, while China and India were at the bottom. Meanwhile, the energy efficiency of the industrial subsector has increased significantly over the past two decades, while that of the other subsectors has been relatively flat. The industrial structure upgrading, per capita GDP, energy consumption structure, and foreign direct investment had significant impacts on energy efficiency with national heterogeneity. Energy consumption structure and GDP per capita were determinative factors of energy efficiency.

Abstract This paper considers a methodology for economic feasibility analysis of a decentralized hybrid WTE (waste-to-energy) system, when input waste streams and technical parameters can be uncertain. A hybrid WTE system is decentralized when there are possibly different owners of the waste treatment units. A two-stage stochastic programming model is proposed to evaluate and optimize the joint probability that each installed unit is able to achieve its own financial target, while adhering to stipulated environmental requirements. A case study is performed based on the city state of Singapore. The results show that, the proposed model can help provide the effective decision support for policy-makers in evaluating the appropriate technological mix of WTE alternatives. Furthermore, the designs generated by the proposed model can significantly improve the economic feasibility of the overall system without sacrificing certain installed unit's financial position. Finally, the optimized hybrid WTE system obtained by the proposed model achieves an optimal mix and balance of implemented treatment technologies, which is more practical than the current incineration only design in the MSW (municipal solid waste) management future in Singapore.