Publications

In Press
Qiang Liu, Fei Teng, Chris P Nielsen, Yuzhong Zhang, and Lixin Wu. In Press. “Large methane mitigation potential through prioritized closure of gas-rich coal mines.” Nature Climate Change.
Jing Cao, Mun S Ho, Rong Ma, and Yu Zhang. In Press. “Transition from plan to market: Imperfect regulations in the electricity sector of China.” Journal of Comparative Economics. Publisher's VersionAbstract
We present evidence on the distortions that arise from imperfect regulations compared with market allocation mechanisms. Using a triple difference strategy, we evaluate the effectiveness of the Energy-Saving Generation Dispatch reform in China, which aims to allocate more generating hours to power plants with higher energy efficiency. We find that the new dispatch rule improved resource allocation within provinces compared with the previous equal-share dispatch rule. However, despite these improvements, the reform fell short of its intended goals because of the failure to strictly implement the merit order based on real-time coal consumption rates. We demonstrate how the lack of compensation for losers, technical requirements for grid stability, the existence of multiple goals, and information costs contribute to imperfect regulation.
2024
Saiwen Zhang, Yiliang Jiang, Shaojun Zhang, and Ernani F Choma. 2024. “Health benefits of vehicle electrification through air pollution in Shanghai, China.” Science of The Total Environment, 914, 1 March 2024, Pp. 169859. Publisher's VersionAbstract
Vehicle electrification has been recognized for its potential to reduce emissions of air pollutants and greenhouse gases in China. Several studies have estimated how national-level policies of electric vehicle (EV) adoption might bring very large environmental and public health benefits from improved air quality to China. However, large-scale adoption is very costly, some regions derive more benefits from large-scale EV adoption than others, and the benefits of replacing internal combustion engines in specific cities is less known. Therefore, it is important for policymakers to design incentives based on regional characteristics – especially for megacities like Shanghai – which typically suffer from worse air quality and where a larger population is exposed to emissions from vehicles. Over the past five years, Shanghai has offered substantial personal subsidies for passenger EVs to accelerate its electrification efforts. Still, it remains uncertain whether EV benefits justify the strength of incentives. The purpose of our study is to evaluate the health and climate benefits of replacing light-duty gasoline vehicles (ICEVs) with battery EVs in the city of Shanghai. We assess health impacts due to ICEV emissions of primary fine particulate matter, NOx, and volatile organic compounds, and to powerplant emissions of NOx and SO2 due to EV charging. We incorporate climate benefits from reduced greenhouse gas emissions based on existing research. We find that the benefit of replacing the average ICEV with an EV in Shanghai is US$6400 (2400-14,700), with health impacts of EVs about 20 times lower than the average ICEV. Larger benefits ensue if older ICEVs are replaced, but replacing newer China ICEVs also achieves positive health benefits. As Shanghai plans to stop providing personal subsidies for EV purchases in 2024, our results show that EVs achieve public health and climate benefits and can help inform policymaking strategies in Shanghai and other megacities.
Jianglong Li, Jinfeng Gao, and Mun Sing Ho. 2024. “Causal effect of aviation on air pollution: An instrumental variable from faraway COVID-19 restrictions in China.” China Economic Review, 84, April 2024, Pp. 102140. Publisher's VersionAbstract
The causal impacts of aviation on local air pollution are poorly understood. Leveraging variation in aviation frequency caused by COVID-19 travel restrictions that occurred hundreds of miles away between 2020 and 2022, this study identifies the short-run effect of aviation on air pollution in Hangzhou, a Chinese megacity. The results demonstrate that a one standard deviation change in aviation is associated with 12% to 21.82% changes in ambient pollution concentrations, with even more substantial pollution effects on downwind days and flights departing from Hangzhou, respectively. These estimates also remain robust to alternative specifications, satisfy external validity beyond Hangzhou and the epidemic period, and exclude pollution spillover effects. We further quantify the welfare losses from aviation pollution and find that people are willing to pay 1.76 US dollars a day in per capita household income for reducing pollution caused by each standard deviation increase in flights (i.e., 134 flights). Further analysis reveals higher economic losses resulting from pollutants at international airports. Our results underscore the need to regulate airborne contaminants from aviation in China urgently.
2023
Xi Lu, Shi Chen, Chris Nielsen, Michael McElroy, Gang He, Shaohui Zhang, Kebin He, Xiu Yang, Fang Zhang, and Jiming Hao. 2023. “Deploying solar photovoltaic energy first in carbon-intensive regions brings gigatons more carbon mitigation by 2060.” Communications Earth & Environment, 4, 369. Publisher's VersionAbstract
The global surge in solar photovoltaic (PV) power has featured spatial specialization from manufacturing to installation along its industrial chain. Yet how to improve PV climate benefits are under-investigated. Here we explore the evolution of net greenhouse gas (GHG) mitigation of PV industry from 2009–2060 with a spatialized-dynamic life-cycle-analysis. Results suggest a net GHG mitigation of 1.29 Gt CO2-equivalent from 2009–2019, achieved by 1.97 Gt of mitigation from installation minus 0.68 Gt of emissions from manufacturing. The highest net GHG mitigation among future manufacturing-installation-scenarios to meet 40% global power demand in 2060 is as high as 204.7 Gt from 2020–2060, featuring manufacturing concentrated in Europe and North America and prioritized PV installations in carbon-intensive nations. This represents 97.5 Gt more net mitigation than the worst-case scenario, equivalent to 1.9 times 2020 global GHG emissions. The results call for strategic international coordination of PV industrial chain to increase GHG net mitigation.
Yu Zhao, Yutong Wang, Yiming Liu, Yueqi Jiang, Bo Zheng, Jia Xing, Yang Liu, Shuai Wang, and Chris Nielsen. 2023. “Sustained emission reductions have restrained the ozone pollution over China.” Nature Geoscience. Publisher's VersionAbstract

Near-surface ozone pollution, associated with complex responses to changing precursor emissions and meteorological conditions, has become one of the biggest challenges in China’s air quality management. Here, we present the spatiotemporal evolution of ozone concentrations from 2010 to 2021 using measurements of the national air quality monitoring network. We evaluate the effectiveness of the national air pollution control programme, including Phase 1 (2013–2017) and Phase 2 (2018–2021), in reducing the ozone level over China, using an optimized machine learning approach, high-resolution emission estimates and an improved air quality model. We find that while emission changes in Phase 1 increased the ozone level over the five highly developed regions, further reductions of nitrogen oxide emissions in Phase 2 have generally constrained the ozone pollution. The changing effect of emission controls on ozone pollution is due to the shift in the prevailing regime for ozone formation and the weakened effects of aerosol declines, as emission reductions continue. We further find that current emission controls have been more effective in rural locales in four of the five regions, and more effective in summer than winter. Therefore, further control of ozone pollution should consider these regional and seasonal variations to identify the most important precursors for the pollution.

Yang Zhao, Ziyue Jiang, Xinyu Chen, Peng Liu, Tianduo Peng, and Zhan Shu. 2023. “Toward environmental sustainability: data-driven analysis of energy use patterns and load profiles for urban electric vehicle fleets.” Energy, 285, 15 Dec 2023, Pp. 129465. Publisher's VersionAbstract
The scale-up of urban electric vehicle (EV) fleets, driven by environmental benefits, is resulting in surging aggregate energy demands that may reshape a city's power supply. This paper establishes an integrated data-driven assessment model for investigating the energy use (kWh) patterns and charging load (kW) profiles of urban-scale EV fleets. To this end, urban EV operating and operational datasets are linked with climate data and vehicle specifications. Four vehicle fleet types are distinguished: private, taxi, rental, and business fleets. Statistical models regarding distribution analysis, spectrum analysis, and identical distribution tests are employed to analyze the patterns of driving distances, energy consumption, and shares of active charging EVs. The minute-level changes in charging EV numbers and aggregate charging power are examined to reflect the grid load impact. The results show that private light-duty EVs in Beijing consume an average of 9.1 kWh/day, with more charging activities on Fridays. The primary load peaks of light-duty EVs in Beijing usually occur between 11 p.m. and 1 a.m., attributable chiefly to the private fleet's midnight peak load estimated at 28 % of the total daily charging private EV count multiplied by 5.5 kW/EV. Secondary peaks occur between 8 a.m. and 10 a.m. on weekdays for private fleets, and at 4 p.m. for public fleets. Our work can be extensively used for analyses on transport emissions, urban power supply, infrastructure build-ups, and policymaking.
Chen Xiang and Qiang Xin. 2023. “Small states as helpless pawns? Panama’s diplomatic strategy over the Taiwan Strait.” Cambridge Review of International Affairs. Publisher's VersionAbstract
A traditional great power stereotype of small states is that of helpless pawns in world politics. After Panama severed its longstanding diplomatic ties with Taiwan in 2017, small state diplomacy once again came under the spotlight. By tracing Panama’s convoluted diplomatic relations over the Taiwan Strait since 1949, we argue that, rather than great power competition alone, it is Panama’s state capacity and its strategic calculations about external threats that account for the shifts in its relations with Taiwan and Mainland China. We further identify five strategies adopted by Panama: bandwagoning, status-seeking, issue linkages, two-sided bargaining, and diplomatic recognition. By bringing agency back into the agent-structure debate, this article shows how, as an agent, Panama has maximised its action space and sheds light on Taiwan administration’s shrinking international recognition against the backdrop of the rising global influence of the People’s Republic of China.
Xiuli Liu, Mun S Ho, Geoffrey JD Hewings, Yuxing Dou, Shouyang Wang, Guangzhou Wang, Dabo Guan, and Shantong Li. 2023. “Aging Population, Balanced Diet and China’s Grain Demand.” Nutrients, 15, 13, Pp. 2877. Publisher's VersionAbstract
The need to make more accurate grain demand (GD) forecasting has become a major topic in the current international grain security discussion. Our research aims to improve short-term GD prediction by establishing a multi-factor model that integrates the key factors: shifts in dietary structures, population size and age structure, urbanization, food waste, and the impact of COVID-19. These factors were not considered simultaneously in previous research. To illustrate the model, we projected China’s annual GDP from 2022 to 2025. We calibrated key parameters such as conversion coefficients from animal foods to feed grain, standard person consumption ratios, and population size using the latest surveys and statistical data that were either out of date or missing in previous research. Results indicate that if the change in diets continued at the rate as observed during 2013–2019 (scenario 1), China’s GD is projected to be 629.35 million tons in 2022 and 658.16 million tons in 2025. However, if diets shift to align with the recommendations in the Dietary Guideline for Chinese Residents 2022 (scenario 2), GD would be lower by 5.9–11.1% annually compared to scenario 1. A reduction in feed grain accounts for 68% of this change. Furthermore, for every 1 percentage point increase in the population adopting a balanced diet, GD would fall by 0.44–0.73 million tons annually during that period. Overlooking changes in the population age structure could lead to an overprediction of annual GDP by 3.8% from 2022 to 2025. With an aging population, China’s GD would fall slightly, and adopting a balanced diet would not lead to an increase in GD but would have positive impacts on human health and the environment. Our sensitivity analysis indicated that reducing food waste, particularly cereal, livestock, and poultry waste, would have significant effects on reducing GD, offsetting the higher demand due to rising urbanization and higher incomes. These results underscore the significance of simultaneous consideration of multiple factors, particularly the dietary structure and demographic composition, resulting in a more accurate prediction of GD. Our findings should be useful for policymakers concerning grain security, health, and environmental protection.
Jing Cao, Mun Ho, and Qingfeng Liu. 2023. “Analyzing multi-greenhouse gas mitigation of China using a general equilibrium model.” Environmental Research Letters, 18, 2, Pp. 025001. Publisher's VersionAbstract
Climate actions have focused on CO2 mitigation and only some studies of China consider non-CO2 greenhouse gases (GHGs), which account for nearly 18% of gross GHG emissions. The economy-wide impact of mitigation covering CO2 and non-CO2 GHGs in China, has not been comprehensively studied and we develop a multi-sector dynamic model to compare the impact of CO2-only mitigation with a multi-GHG mitigation policy that also price non-CO2 GHGs. We find that the multi-GHG approach significantly reduces the marginal abatement cost and economic loss to reach the same level of GHG emissions (measures as 100 year global warming potential) compared to a CO2-only scenario. By 2060, multi-gas mitigation can reduce the tax rate by 15.44% and improve real gross domestic product (GDP) by 0.41%. The aggregate gain brought by multi-GHG mitigation are robust to various pathways and but vary across periods and sectors.
Xinyang Guo, Xinyu Chen, Xia Chen, Peter Sherman, Jinyu Wen, and Michael McElroy. 2023. “Grid integration feasibility and investment planning of offshore wind power under carbon-neutral transition in China.” Nature Communications, 14, 2447. Publisher's VersionAbstract
Offshore wind power, with accelerated declining levelized costs, is emerging as a critical building-block to fully decarbonize the world’s largest CO2 emitter, China. However, system integration barriers as well as system balancing costs have not been quantified yet. Here we develop a bottom-up model to test the grid accommodation capabilities and design the optimal investment plans for offshore wind power considering resource distributions, hourly power system simulations, and transmission/storage/hydrogen investments. Results indicate that grid integration barriers exist currently at the provincial level. For 2030, optimized offshore wind investment levels should be doubled compared with current government plans, and provincial allocations should be significantly improved considering both resource quality and grid conditions. For 2050, offshore wind capacity in China could reach as high as 1500 GW, prompting a paradigm shift in national transmission structure, favoring long-term storage in the energy portfolio, enabling green hydrogen production in coastal demand centers, resulting in the world’s largest wind power market.
Mun S Ho, Koji Nomura, and Jon D Samuels. 2023. “The growing impact of ICT productivity via the cost of capital: Evidence from the U.S. and Japan.” Telecommunications Policy, 47, 9, Pp. 102635. Publisher's VersionAbstract
We identify and measure two impacts of industry-level total factor productivity(TFP) growth on aggregate price change in the U.S. and Japan. The first is a standard effect from the definition of aggregate GDP. TFP change lowers aggregate prices ceteris paribus. The second is that a change in TFP in the production of investment goods lowers the cost of capital via lower investment prices. We call this the cost-of-capital effect and formulate an expanded growth accounting framework to capture both effects. We apply it to a harmonized dataset for the two countries and find that the standard effect has fallen since the peak around 2000 due to lower TFP growth and a diminished share of GDP. However, the cost-of-capital effect has risen in importance and offsets part of this decline in the standard effect.
Lu Liu, Yu Zhao, Hongyan Zhao, Yifei Wang, and Chris P Nielsen. 2023. “Impacts of Receiving International Industrial Transfer on China’s Air Quality and Health Exceed Those of Export Trade.” Environmental Science & Technology, 2023, Pp. 16989–16998. Publisher's VersionAbstract
Benefiting from international economic cooperation on income, technology diffusion, and employment, China also suffers its environmental and health impacts, from both international trade (IT), as is now widely understood, and international industrial transfer (IIT), which has been largely unrecognized. Here, we develop a comprehensive framework to estimate the impacts of exporting IT and receiving IIT. We find that China’s emissions of CO2 and almost all air pollutants associated with IIT and IT together grew after 1997 but then declined after 2010, with the peak shares of national total emissions ranging 18–31% for different species. These sources further accounted for 3.8% of nationwide PM2.5 concentrations and 94,610 (76,000–112,040) premature deaths in 2012, and the values declined to 2.6% and 67,370 (52,390–81,810), respectively, for 2017. Separated, the contribution of IIT to those impacts was more than twice that of IT. Scenario analyses suggest that improving emission controls in its less-developed regions would effectively reduce the impact of economic globalization, but such a benefit could be largely offset by strengthened international economic cooperation. The outcomes provide a scientific basis for adjusting China’s strategic roles in the international distribution of industrial production and its formulation of relevant environmental policies from a comprehensive perspective.
Jingran Zhang, Yiliang Jiang, Yunjie Wang, Shaojun Zhang, Ye Wu, Shuxiao Wang, Chris P Nielsen, Michael B McElroy, and Jiming Hao. 2023. “Increased Impact of Aviation on Air Quality and Human Health in China.” Environmental Science & Technology, 2023, Pp. 19575–19583. Publisher's VersionAbstract
China’s civil aviation market has rapidly expanded, becoming the world’s second-largest. However, the air quality and health impacts caused by its aircraft emissions have been inadequately assessed. Here, we leverage an updated emission inventory of air pollutants with improved temporal and spatial resolution based on hundreds of thousands of flight trajectories and simulate aviation-attributable contributions to ground-level air pollution in China. We find that in 2017, the annual-average aviation-attributed PM2.5 and O3 concentrations were 0.4–1.5 and 10.6–14.5 μg·m–3, respectively, suggesting that aviation emissions have become an increasingly important source of ambient air pollution. The contributions attributable to high-altitude emissions (climb/cruise/descent) were comparable to those at low altitudes (landing and takeoff). Aviation-attributed ambient PM2.5 and O3 exposures are estimated to have caused about 67,000 deaths in China in 2017, with populous coastal regions in Eastern China suffering the most due to the dense aviation activity. We recommend that industrial and policy stakeholders expedite an agenda of regulating air pollutants harmonized with decarbonization efforts for a more sustainable aviation future.
Meng Gao, Fan Wang, Yihui Ding, Zhiwei Wu, YangYang Xu, Xiao Lu, Zifa Wang, Gregory R. Carmichael, and Michael B McElroy. 2023. “Large-scale climate patterns offer pre-seasonal hints on the co-occurrence of heat wave and O3 pollution in China.” Proceedings of the National Academy of Sciences (PNAS), 120, 26, Pp. e2218274120. Publisher's VersionAbstract

Heat waves and air pollution extremes exert compounding effects on human health and food security and may worsen under future climate change. On the basis of reconstructed daily O3 levels in China and meteorological reanalysis, we found that the interannual variability of the frequency of summertime co-occurrence of heat wave and O3 pollution in China is regulated mainly by a combination of springtime warming in the western Pacific Ocean, western Indian Ocean, and Ross Sea. These sea surface temperature anomalies impose influences on precipitation, radiation, etc., to modulate the co-occurrence, which were also confirmed with coupled chemistry–climate numerical experiments. We thus built a multivariable regression model to predict co-occurrence a season in advance, and correlation coefficient could reach 0.81 (P < 0.01) for the North China Plain. Our results provide useful information for the government to take actions in advance to mitigate damage from these synergistic costressors.

Heat waves and air pollution are two prominent threats, both of which have been reported to cause public health and ecosystem crises, particularly under rapid urbanization and global warming (12). Heat waves, defined as consecutive days of excessively high atmosphere-related heat stress (34), adversely influence human health by impacting respiratory and cardiovascular systems. Heat waves are linked with high O3 episodes that harm human health and vegetation (57). In warm seasons, heat waves and extreme O3 events often occur simultaneously due to common driving meteorological conditions, i.e., stagnant high-pressure systems that favor accumulation of heat and O3 precursors (8). Besides, complex chemistry–climate feedbacks through biogenic emissions (source) and uptake by plants (sink) could exacerbate co-occurrence of heat wave and O3 extremes (9). It is imperative to understand driving factors for the co-occurrence of heat and O3 extremes, as accumulating evidence suggests amplified health outcomes beyond the sum of individual effects (1012). Analitis et al. (13) reported that the number of daily deaths during heat wave episodes was 54% higher on high O3 days compared with low O3 days.

Previous studies have linked occurrences of heat waves or O3 extremes, separately, with large-scale atmospheric circulation or sea surface temperature (SST) anomalies (1420). For instance, Zhu et al. (17) demonstrated that the frequency and variability of summertime heat waves over North America was closely associated with SST anomalies in the tropical Atlantic and tropical western Pacific in spring and El Niño–Southern Oscillation phase change. Shen and Mickley (21) showed that O3 concentration in Eastern United States was linked with warm tropical Atlantic SST and cold northeast Pacific SST, as well as positive sea-level pressure (SLP) anomalies over central Pacific and negative SLP anomalies over the Atlantic and North America. However, the climate factors modulating the co-occurrence of heat and O3 extremes at a regional level remain unclear and had only been the subject of limited studies (82224).

With roughly one-sixth of the world’s population and rapid energy-intensive development, China is facing the dual challenge of air pollution and climate change (2526). Central and Eastern China, especially the North China Plain (NCP), experienced improved PM2.5 air quality over past years due to the implementation of the most stringent clean air policy, but now suffers from largest increases in summertime O3 exposure (27). O3 concentrations in the NCP enhanced at almost twice the average pace across China (28). An amplified upward trend of the joint occurrences of heat and O3 extremes has been identified in China over 2013 to 2020 (29). Understanding the driving climate factors for its interannual variability would contribute to long-term planning of control of costressors. Characterizing interannual variability also enables prediction which could allow sufficient time for mitigation of the interactive damages from joint exposure (213033). Previously, we demonstrated the possibility of seasonal prediction of wintertime aerosol pollution in India (34). Considering the strong linkages between O3 level and climate patterns, we argue here that it may also be possible to predict co-occurrence of heat waves and O3 pollution, potentially up to several years in advance, considering the active efforts in developing reliable seasonal (months ahead) and even longer prediction of climate variability (35).

In this study, we aim to identify leading patterns that control the spatiotemporal variability of occurrence frequency (days in a year) of joint heat wave and O3 pollution events (HWOP). We focus on Central and Eastern China (17.5°N to 47.5°N, 98°E to 125°E), where over 80% Chinese population reside and co-occurrences of HWOP events are prominent. Climate drivers are identified by empirical orthogonal function (EOF), which decomposes historical spatiotemporal variations of HWOP frequency that inferred with atmospheric reanalysis and reconstructed daily O3 datasets. Findings from statistical analyses are further supported by numerical model experiments using the state-of-the-art Community Earth System Model version 2.1.3 (CESM v2.1.3). Encouraged by the robustness of the identified teleconnections between co-occurrence events and SST anomalies, we further build a regression-based statistical model to predict summertime HWOP a season in advance, improving our capability in the management of these important health and vegetation costressors.

 

Jing Cao and Rong Ma. 2023. “Mitigating agricultural fires with carrot or stick? Evidence from China.” Journal of Development Economics, 165, October 2023, Pp. 103173. Publisher's VersionAbstract
This paper examines the effects of biomass power plants (BPPs) on farmers’ use of agricultural fires for land clearance in China from 2001 to 2019. We show that the entry of BPPs leads to a significant reduction of agricultural fires by 14%. Farmers near BPPs display stronger responses, leading to a more significant reduction in straw burning, especially during high agricultural fire seasons. The notable decline in agricultural fires is likely driven by economic incentives provided by BPPs to farmers for collecting crop straw from their land. Additionally, straw-burning bans have limited effectiveness in reducing total agricultural fires, but they appear to reduce straw burning during nighttime, when the monitoring of agricultural fires is easier. We also provide evidence that local air quality has markedly improved, resulting in substantial health benefits that surpass the social benefits of reducing carbon emissions.
Yu Fu, Haiyang Lin, Biao Feng, Cuiping Ma, Qie Sun, and Ronald Wennersten. 2023. “Off-design characteristics of energy conversion equipment in integrated energy systems.” Journal of Cleaner Production, 407, 25 June 2023, Pp. 136941. Publisher's VersionAbstract

With the increasing penetration of variable renewable energyintegrated energy systems (IES) have become increasingly complex. Unfortunately, the widely used constant efficiency model is too simplified to reflect actual operating conditions. Therefore, this study investigated the effects of off-design characteristics on the operation and configuration of integrated energy systems, both singly and collectively. To this aim, a two-stage optimization framework was applied to optimize the operation and configuration of IES. The off-design characteristics include the electric-thermal correlation of gas turbines (GTs), the load rate-efficiency correlation of gas boilers (GBs) and absorption chillers (ACs), and the temperature-efficiency correlation of heat pumps (HPs) and electric chillers (ECs).

When off-design characteristics are considered, the optimal capacities of the energy conversion equipment tend to increase and system costs would increase. For all system equipment, the capacity of the EC increases by 515.4% and the system cost increases by 7.3%. Regarding system operation, the effects of off-design characteristics on the operation of the GT and AC are most significant for all energy conversion equipment. The electric energy storage (EES) and the thermal energy storage (TES) help to reduce the capacity of the GT and system cost. When off-design characteristics are considered, their effects are magnified.

Jialin Liu, Fangyan Cheng, Róisín Commane, Yi Zhu, Weiwen Ji, Xiuling Man, Chenghe Guan, and J. William Munger. 2023. “Quantifying an overlooked deciduous-needleleaf carbon sink at the southern margin of the Central-Siberian Permafrost Zone.” Journal of Geophysical Research: Biogeosciences. Publisher's VersionAbstract

With over 700 million km2 Siberia is the largest expanse of the northern boreal forest—deciduous-needleleaf larch. Temperatures are increasing across this region, but the consequences to carbon balances are not well understood for larch forests. We present flux measurements from a larch forest near the southern edge of Central-Siberia where permafrost degradation and ecosystem shifts are already observed. Results indicate net carbon exchanges are influenced by the seasonality of permafrost active layers, temperature and humidity, and soil water availability. During periods when surface soils are fully thawed, larch forest is a significant carbon sink. During the spring-thaw and fall-freeze transition, there is a weak signal of carbon uptake at mid-day. Net carbon exchanges are near-zero when the soil is fully frozen from the surface down to the permafrost. We fit an empirical ecosystem functional model to quantify the dependence of larch-forest carbon balance on climatic drivers. The model provides a basis for ecosystem carbon budgets over time and space. Larch differs from boreal evergreens by having higher maximum productivity and lower respiration, leading to an increased carbon sink. Comparison to previous measurements from another northern larch site suggests climate change will result in an increased forest carbon sink if the southern larch subtype replaces the northern subtype. Observations of carbon fluxes in Siberian larch are still too sparse to adequately determine age dependence, inter-annual variability, and spatial heterogeneity though they suggest that boreal larch accounts for a larger fraction of global carbon uptake than has been previously recognized.

Plain Language Summary

Cold, wet soils in boreal forests contain a large amount of carbon. However, warmer temperatures coupled with changes in hydrology could release stored carbon and accelerate its decomposition. The boreal spruce and pine forests in North America and Fennoscandia have been studied extensively, but observations in the Siberian larch forests are limited. Because larch shed their needles in winter their response to changing temperature and moisture may differ from expectations based on evergreen conifers. Our work focuses on a larch forest in northern China that is at the southern edge of the Central-Siberian biome where eco-environmental changes are starting to occur. By studying how the annual growth and carbon balance in this forest respond to variations in weather we will be better able to predict significant changes in the structure and function of the larch ecosystem that could undermine regional ecosystem stability. Larch forest functions differently from evergreen needle-leaf forests and provides the larger carbon sink than had been previously recognized.

Key Points

  • Seasonality in permafrost active layer and environmental temperature-humidity dynamics closely regulate boreal larch’ carbon cycle

  • Ecosystem functional traits in deciduous larch are distinct from other boreal needleleaf evergreens

  • By inadequately accounting for boreal larch's carbon sink, the estimates of global forest carbon budgets will be biased low

Faan Chen, Yaxin Li, Qianqian Feng, Zehao Dong, Yiming Qian, Yi Yan, Mun S. Ho, Qianchen Ma, Dashan Zhang, and Yuanzhe Jin. 2023. “Road safety performance rating through PSI-PRIDIT: A planning tool for designing policies and identifying best practices for EAS countries.” Socio-Economic Planning Sciences. Publisher's VersionAbstract
Road traffic injuries are a leading cause of socio-economic loss in East Asia Summit (EAS) countries. A regular performance rating to monitor progress and calibrate interventions is crucial for road safety improvement, helping to save human lives and reducing economic losses. To this end, we propose a new and easy-to-adapt multi-criteria decision-making method for systematically rating the road safety performance of the EAS countries, the preference selection index with principal component analysis of RIDIT scores (PSI-PRIDIT) (scores of a distribution relative to an identified distribution integral transformation). Using the results from other classical methods as a reference, we rank the EAS countries robustly and place them into three groups over the last decade (2009–2019), based on the composite road safety development index. Our findings should be useful for EAS countries to detect underlying problems and identify best practices, as well as provide government officials, policymakers, and practitioners with meaningful guidelines on the adoption of successful road safety measures. Overall, the proposed rating framework should help to strengthen the institutional capacity for road safety management and addresses road safety issues.
2022
Xi Yang, Chris P. Nielsen, Shaojie Song, and Michael B. McElroy. 2022. “Breaking the “hard-to-abate” bottleneck in China’s path to carbon neutrality with clean hydrogen.” Nature Energy, 7, Pp. 955–965. Publisher's VersionAbstract
Countries such as China are facing a bottleneck in their paths to carbon neutrality: abating emissions in heavy industries and heavy-duty transport. There are few in-depth studies of the prospective role for clean hydrogen in these ‘hard-to-abate’ (HTA) sectors. Here we carry out an integrated dynamic least-cost modelling analysis. Results show that, first, clean hydrogen can be both a major energy carrier and feedstock that can significantly reduce carbon emissions of heavy industry. It can also fuel up to 50% of China’s heavy-duty truck and bus fleets by 2060 and significant shares of shipping. Second, a realistic clean hydrogen scenario that reaches 65.7 Mt of production in 2060 could avoid US$1.72 trillion of new investment compared with a no-hydrogen scenario. This study provides evidence of the value of clean hydrogen in HTA sectors for China and countries facing similar challenges in reducing emissions to achieve net-zero goals.

Pages