Atmospheric Emissions

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《Nature Index 2016 Collaborations》杂志刊专文报道哈佛大学中国项目

October 30, 2016

《Nature Index》 2016期刊刊登封面文章专门介绍了哈佛大学中国项目,作为国际科研合作的成功范例。该文引述了Mike McElroy教授和Bill Munger研究员的话,重点介绍了哈佛大学中国项目所支持的碳循环研究,该研究是基于北京近郊的大气监测站以及多个位于美国和中国林区的监测站的观测数据展开的。Nature Index也为这项研究同步摄制了一部短片,片中在哈佛森林实地采访了资深研究员Bill Munger以及两名参与该项研究的学生刘家霖和Archana Dayalu。
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《经济学人》、《中国日报》报道哈佛大学中国项目的研究;《纽约时报》就同一主题刊登专栏文章

March 14, 2014

《中国日报》对哈佛大学中国项目的碳定价和空气污染研究进行报道;《经济学人》杂志引述我们项目专著《中国更晴朗的天空》(Clearer Skies Over China) 中关于中国二氧化硫排放控制的有效性的研究结论,同时项目研究人员Chris Nielsen先生与何文胜博士也在《纽约时报》就同一主题撰写专栏文章。
... Read more about 《经济学人》、《中国日报》报道哈佛大学中国项目的研究;《纽约时报》就同一主题刊登专栏文章

smog in china nytimes

《纽约时报》报道哈佛大学中国项目调研及研讨会

July 14, 2014

区域性气候的不断变化有可能增加中国华北地区入冬后的大气静稳现象,并因此导致了近来的极端雾霾天气。这是中国及国际大气科学学术界都在积极研究的课题,也是哈佛大学中国项目举办的主题为 “中国2035年:能源、气候与发展”的研讨会上的议题之一——该研讨会于2014年6月18日至19日在哈佛上海中心召开,集结了中国顶尖的科学家、经济学家和政策分析家。
... Read more about 《纽约时报》报道哈佛大学中国项目调研及研讨会

Nielsen总监在《环境与健康展望》期刊表示中国细颗粒物(PM2.5)变化趋势令人鼓舞

Nielsen总监在《环境与健康展望》期刊表示中国细颗粒物(PM2.5)变化趋势令人鼓舞

February 29, 2016

《环境与健康展望》期刊 (Environmental Health Perspectives)援引哈佛大学中国项目执行总监Chris Nielsen先生的观点:与大众普遍的认知相反,根据卫星观测,自2007年开始,中国大部分地区细颗粒物(PM2.5)浓度的年平均值已经下降。... Read more about Nielsen总监在《环境与健康展望》期刊表示中国细颗粒物(PM2.5)变化趋势令人鼓舞

Yu Zhao, Chris P Nielsen, Michael B. McElroy, Lin Zhang, and Jie Zhang. 2012. “CO emissions in China: Uncertainties and implications of improved energy efficiency and emission control.” Atmospheric Environment, 49, Pp. 103-113. Publisher's VersionAbstract
A bottom-up methodology and an improved database of emission factors combining the latest domestic field measurements are developed to estimate the emissions of anthropogenic CO from China at national and provincial levels. The CO emission factors for major economic sectors declined to varying degrees from 2005 to 2009, attributed to improved energy efficiency and/or emission control regulations. Total national CO emissions are estimated at 173 Tg for 2005 and have been relatively stable for subsequent years, despite fast growth of energy consumption and industrial production. While industry and transportation sources dominated CO emissions in developed eastern and north-central China, residential combustion played a much greater role in the less developed western provinces. The uncertainties of national Chinese CO emissions are quantified using Monte Carlo simulation at −20% to +45% (95% confidence interval). Due to poor understanding of emission factors and activity levels for combustion of solid fuels, the largest uncertainties are found for emissions from the residential sector. The trends of bottom-up emissions compare reasonably to satellite observation of CO columns and to ground observations of CO2–CO correlation slopes. The increase in the ratio for emissions of CO2 relative to CO suggests that China has successfully improved combustion efficiencies across its economy in recent years, consistent with national policies to improve energy efficiency and to control criteria air pollutants.
Jing Cao, Richard Garbaccio, and Mun S Ho. 2009. “China's 11th Five-Year Plan and the environment: Reducing SO2 emissions.” Review of Environmental Economics and Policy, 3, 2, Pp. 189-208. Publisher's VersionAbstract
China's rapid economic growth has been accompanied by a high level of environmental degradation. One of the major sources of health and ecosystem damages is sulfur dioxide (SO2). Reducing SO2 emissions is a priority of China's environmental authorities, and the 11th Five-Year Plan (2006–2010) includes the target of reducing total SO2 emissions by 10 percent from the 2005 level. Given the rapid increase in SO2 emissions that is expected to occur in absence of intervention, attaining this target will require a significant effort. This article examines the two major policy measures the government is taking to achieve the SO2 target: a shutdown of many small, inefficient power plants and the installation of desulfurization equipment on existing and new coal-fired plants. We present results from a joint U.S.–China study that we participated in, which estimated the costs and benefits of these policies. We then estimate the economy-wide impacts of the two policies using a multisector model of the Chinese economy. We find that in the aggregate, the economic benefits of the shutdown of the small power plants are large enough to offset the costs of the desulfurization equipment, even without considering the substantial environmental benefits from the reduction of emissions of SO2 and other pollutants.
Yu Lei, Qiang Zhang, Kebin He, and David G Streets. 2011. “Primary anthropogenic aerosol emission trends for China, 1990-2005.” Atmospheric Chemistry and Physics, 11, Pp. 931-954. Publisher's VersionAbstract
An inventory of anthropogenic primary aerosol
emissions in China was developed for 1990–2005 using a
technology-based approach. Taking into account changes
in the technology penetration within industry sectors and
improvements in emission controls driven by stricter emission
standards, a dynamic methodology was derived and implemented
to estimate inter-annual emission factors. Emission
factors of PM2.5 decreased by 7%–69% from 1990 to
2005 in different industry sectors of China, and emission factors
of TSP decreased by 18%–80% as well, with the measures
of controlling PM emissions implemented. As a result,
emissions of PM2.5 and TSP in 2005 were 11.0 Tg and
29.7 Tg, respectively, less than what they would have been
without the adoption of these measures. Emissions of PM2.5,
PM10 and TSP presented similar trends: they increased in
the first six years of 1990s and decreased until 2000, then
increased again in the following years. Emissions of TSP
peaked (35.5 Tg) in 1996, while the peak of PM10 (18.8 Tg)
and PM2.5 (12.7 Tg) emissions occurred in 2005. Although
various emission trends were identified across sectors, the cement
industry and biofuel combustion in the residential sector
were consistently the largest sources of PM2.5 emissions,
accounting for 53%–62% of emissions over the study period.
The non-metallic mineral product industry, including the cement,
lime and brick industries, accounted for 54%–63% of
national TSP emissions. There were no significant trends of
BC and OC emissions until 2000, but the increase after 2000
Correspondence to: K. B. He
(hekb@tsinghua.edu.cn)
brought the peaks of BC (1.51 Tg) and OC (3.19 Tg) emissions
in 2005. Although significant improvements in the estimation
of primary aerosols are presented here, there still
exist large uncertainties. More accurate and detailed activity
information and emission factors based on local tests are essential
to further improve emission estimates, this especially
being so for the brick and coke industries, as well as for coalburning
stoves and biofuel usage in the residential sector.
Clearer Skies Over China: Reconciling Air Pollution, Climate, and Economic Goals
2013. Clearer Skies Over China: Reconciling Air Pollution, Climate, and Economic Goals. Cambridge, MA: MIT Press. Publisher's VersionAbstract

A groundbreaking U.S.–Chinese inquiry into the effects of recent air pollution controls and prospective carbon taxes on China's economy and environment.

China's carbon dioxide emissions now outstrip those of other countries and its domestic air quality is severely degraded, especially in urban areas. Its sheer size and its growing, fossil-fuel-powered economy mean that China's economic and environmental policy choices will have an outsized effect on the global environmental future. Over the last decade, China has pursued policies that target both fossil fuel use and atmospheric emissions, but these efforts have been substantially overwhelmed by the country's increasing energy demands. With a billion citizens still living on less than $4,000 per year, China's energy and environmental policies must be reconciled with the goals of maintaining economic growth and raising living standards.

This book, a U.S.–Chinese collaboration of experts from Harvard and Tsinghua University, offers a groundbreaking integrated analysis of China's economy, emissions, air quality, public health, and agriculture. It first offers essential scientific context and accessible summaries of the book's policy findings; it then provides the underlying scientific and economic research. These studies suggest that China's recent sulfur controls achieved enormous environmental health benefits at unexpectedly low costs. They also indicate that judicious implementation of carbon taxes could reduce not only China's carbon emissions but also its air pollution more comprehensively than current single-pollutant policies, all at little cost to economic growth.

Yu Zhao, Chris P Nielsen, Yu Lei, Michael B. McElroy, and Jiming Hao. 2011. “Quantifying the uncertainties of a bottom-up emission inventory of anthropogenic atmospheric pollutants in China.” Atmospheric Chemistry and Physics, 11, Pp. 2295-2308. Publisher's VersionAbstract
The uncertainties of a national, bottom-up inventory
of Chinese emissions of anthropogenic SO2, NOx, and
particulate matter (PM) of different size classes and carbonaceous
species are comprehensively quantified, for the first
time, using Monte Carlo simulation. The inventory is structured
by seven dominant sectors: coal-fired electric power,
cement, iron and steel, other industry (boiler combustion),
other industry (non-combustion processes), transportation,
and residential. For each parameter related to emission factors
or activity-level calculations, the uncertainties, represented
as probability distributions, are either statistically fitted
using results of domestic field tests or, when these are
lacking, estimated based on foreign or other domestic data.
The uncertainties (i.e., 95% confidence intervals around the
central estimates) of Chinese emissions of SO2, NOx, total
PM, PM10, PM2.5, black carbon (BC), and organic carbon
(OC) in 2005 are estimated to be −14%13%, −13%37%,
−11%38%, −14%45%, −17%54%, −25%136%,
and −40%121%, respectively. Variations at activity levels
(e.g., energy consumption or industrial production) are
not the main source of emission uncertainties. Due to narrow
classification of source types, large sample sizes, and
relatively high data quality, the coal-fired power sector is estimated
to have the smallest emission uncertainties for all
species except BC and OC. Due to poorer source classifications
and a wider range of estimated emission factors,
considerable uncertainties of NOx and PM emissions from
cement production and boiler combustion in other industries
are found. The probability distributions of emission
factors for biomass burning, the largest source of BC and
OC, are fitted based on very limited domestic field measurements,
and special caution should thus be taken interpreting
these emission uncertainties. Although Monte Carlo simulation
yields narrowed estimates of uncertainties compared
to previous bottom-up emission studies, the results are not
always consistent with those derived from satellite observations.
The results thus represent an incremental research
advance; while the analysis provides current estimates of
uncertainty to researchers investigating Chinese and global
atmospheric transport and chemistry, it also identifies specific
needs in data collection and analysis to improve on
them. Strengthened quantification of emissions of the included
species and other, closely associated ones – notably
CO2, generated largely by the same processes and thus subject
to many of the same parameter uncertainties – is essential
not only for science but for the design of policies to redress
critical atmospheric environmental hazards at local, regional,
and global scales.
Xi Lu, Michael B. McElroy, Gang Wu, and Chris P Nielsen. 2012. “Accelerated reduction of SO2 emissions from the US power sector triggered by changing prices of natural gas.” Environmental Science and Technology, 46, 14, Pp. 7882-7889. Publisher's VersionAbstract
Emissions of sulfur dioxide (SO2) from the U.S. power sector decreased by 24% in 2009 relative to 2008. The Logarithmic Mean Divisia Index (LMDI) approach was applied to isolate the factors responsible for this decrease. It is concluded that 15% of the decrease can be attributed to the drop in demand for electricity triggered by the economic recession, and 28% can be attributed to switching of fuel from coal to gas responding to the decrease in prices for the latter. The largest factor in the decrease, close to 57%, resulted from an overall decline in emissions per unit of power generated from coal. This is attributed in part to selective idling of older, less efficient coal plants that generally do not incorporate technology for sulfur removal, and in part to continued investments by the power sector in removal equipment in response to the requirements limiting emissions imposed by the U.S. Environmental Protection Agency (U.S. EPA). The paper argues further that imposition of a modest tax on emissions of carbon would have ancillary benefits in terms of emissions of SO2.

Final Manuscript in DASH
This paper is from a series investigating and comparing the prospects for low- and non-carbon power generation in China and the U.S.

Yu Zhao, Michael B. McElroy, Jia Xing, Lei Duan, Chris P Nielsen, Yu Lei, and Jiming Hao. 2011. “Multiple effects and uncertainties of emission control policies in China: Public health, soil acidification, and global temperature.” Science of the Total Environment , 409, 24, Pp. 5177-5187. Publisher's VersionAbstract
Policies to control emissions of criteria pollutants in China may have conflicting impacts on public health, soil acidification, and climate. Two scenarios for 2020, a base case without anticipated control measures and a more realistic case including such controls, are evaluated to quantify the effects of the policies on emissions and resulting environmental outcomes. Large benefits to public health can be expected from the controls, attributed mainly to reduced emissions of primary PM and gaseous PM precursors, and thus lower ambient concentrations of PM2.5. Approximately 4% of all-cause mortality in the country can be avoided (95% confidence interval: 1–7%), particularly in eastern and north-central China, regions with large population densities and high levels of PM2.5. Surface ozone levels, however, are estimated to increase in parts of those regions, despite NOX reductions. This implies VOC-limited conditions. Even with significant reduction of SO2 and NOX emissions, the controls will not significantly mitigate risks of soil acidification, judged by the exceedance levels of critical load (CL). This is due to the decrease in primary PM emissions, with the consequent reduction in deposition of alkaline base cations. Compared to 2005, even larger CL exceedances are found for both scenarios in 2020, implying that PM control may negate any recovery from soil acidification due to SO2 reductions. Noting large uncertainties, current polices to control emissions of criteria pollutants in China will not reduce climate warming, since controlling SO2 emissions also reduces reflective secondary aerosols. Black carbon emission is an important source of uncertainty concerning the effects of Chinese control policies on global temperature change. Given these conflicts, greater consideration should be paid to reconciling varied environmental objectives, and emission control strategies should target not only criteria pollutants but also species such as VOCs and CO2.
Yu Zhao, Chris P Nielsen, and Michael B. McElroy. 2012. “China's CO2 emissions estimated from the bottom up: Recent trends, spatial distributions, and quantification of uncertainties.” Atmospheric Environment, 59, Pp. 214-223. Publisher's VersionAbstract
China's emissions of anthropogenic CO2 are estimated using a bottom-up emission inventory framework based on a detailed categorization of economic sectors and provincial economic and energy data. It includes a newly compiled database of CO2 emission factors employing the latest field study results from China. Total annual emissions are estimated to have risen from 7126 to 9370 Mt CO2 from 2005 to 2009. Recent policies to conserve energy and reduce emissions have been effective in limiting CO2 emissions from power and iron & steel plants, but have had little effect on those from cement production. The uncertainties of China's CO2 emissions are quantified for the first time using Monte-Carlo simulation, producing a 95% confidence interval (CI) of −9% to +11% for total emissions in 2005. The largest contributors to sector-level emission uncertainty are emission factors for most industrial sources and activity levels for power plants, transportation, and residential & commercial sources. Application of province-level energy consumption and China-specific emission factors in some sectors results in higher annual emission estimates for 2005-2008 as compared with other studies, although most of those are within the 95% CIs of this study.
Yu Zhao, Shuxiao Wang, Chris P Nielsen, Xinghua Li, and Jiming Hao. 2010. “Establishment of a database of emission factors for atmospheric pollutant emissions from Chinese coal-fired power plants.” Atmospheric Environment, 44, 12, Pp. 1515-1523. Publisher's VersionAbstract
Field measurements and data investigations were conducted for developing an emission factor database for inventories of atmospheric pollutants from Chinese coal-fired power plants. Gaseous pollutants and particulate matter (PM) of different size fractions were measured using a gas analyzer and an electric low-pressure impactor (ELPI), respectively, for ten units in eight coal-fired power plants across the country. Combining results of field tests and literature surveys, emission factors with 95% confidence intervals (CIs) were calculated by boiler type, fuel quality, and emission control devices using bootstrap and Monte Carlo simulations. The emission factor of uncontrolled SO2 from pulverized combustion (PC) boilers burning bituminous or anthracite coal was estimated to be 18.0S kg t−1 (i.e., 18.0 × the percentage sulfur content of coal, S) with a 95% CI of 17.2S–18.5S. NOX emission factors for pulverized-coal boilers ranged from 4.0 to 11.2 kg t−1, with uncertainties of 14–45% for different unit types. The emission factors of uncontrolled PM2.5, PM10, and total PM emitted by PC boilers were estimated to be 0.4A (where A is the percentage ash content of coal), 1.5A and 6.9A kg t−1, respectively, with 95% CIs of 0.3A–0.5A, 1.1A–1.9A and 5.8A–7.9A. The analogous PM values for emissions with electrostatic precipitator (ESP) controls were 0.032A (95% CI: 0.021A–0.046A), 0.065A (0.039A–0.092A) and 0.094A (0.0656A–0.132A) kg t−1, and 0.0147A (0.0092–0.0225A), 0.0210A (0.0129A–0.0317A), and 0.0231A (0.0142A–0.0348A) for those with both ESP and wet flue-gas desulfurization (wet-FGD). SO2 and NOX emission factors for Chinese power plants were smaller than those of U.S. EPA AP-42 database, due mainly to lower heating values of coals in China. PM emission factors for units with ESP, however, were generally larger than AP-42 values, because of poorer removal efficiencies of Chinese dust collectors. For units with advanced emission control technologies, more field measurements are needed to reduce emission factor uncertainties.
Yu Lei, Qiang Zhang, Chris P Nielsen, and Kebin He. 2011. “An inventory of primary air pollutants and CO2 emissions from cement production in China, 1990-2020.” Atmospheric Environment, 45, 1, Pp. 147-154. Publisher's VersionAbstract
Direct emissions of air pollutants from the cement industry in China were estimated by developing a technology-based methodology using information on the proportion of cement produced from different types of kilns and the emission standards for the Chinese cement industry. Historical emissions of sulfur dioxide (SO2), nitrogen oxides (NOX), carbon monoxide (CO), particulate matter (PM) and carbon dioxide (CO2) were estimated for the years 1990–2008, and future emissions were projected up to 2020 based on current energy-related and emission control policies. Compared with the historical high (4.36 Tg of PM2.5, 7.16 Tg of PM10 and 10.44 Tg of TSP in 1997), PM emissions are predicted to drop substantially by 2020, despite the expected tripling of cement production. Certain other air pollutant emissions, such as CO and SO2, are also predicted to decrease with the progressive closure of shaft kilns. NOX emissions, however, could increase because of the promotion of precalciner kilns and the rapid increase of cement production. CO2 emissions from the cement industry account for approximately one eighth of China’s national CO2 emissions. Our analysis indicates that it is possible to reduce CO2 emissions from this industry by approximately 12.8% if advanced energy-related technologies are implemented. These technologies will bring co-benefits in reducing other air pollutants as well.
Xi Lu, Michael B. McElroy, Chris P Nielsen, Xinyu Chen, and Junling Huang. 2013. “Optimal integration of offshore wind power for a steadier, environmentally friendlier, supply of electricity in China.” Energy Policy, 62, Pp. 131–138. Publisher's VersionAbstract

Demand for electricity in China is concentrated to a significant extent in its coastal provinces. Opportunities for production of electricity by on-shore wind facilities are greatest, however, in the north and west of the country. Using high resolution wind data derived from the GEOS-5 assimilation, this study shows that investments in off-shore wind facilities in these spatially separated regions (Bohai-Bay or BHB, Yangtze-River Delta or YRD, Pearl-River Delta or PRD) could make an important contribution to overall regional demand for electricity in coastal China. An optimization analysis indicates that hour-to-hour variability of outputs from a combined system can be minimized by investing 24% of the power capacity in BHB, 30% in YRD and 47% in PRD. The analysis suggests that about 28% of the overall off-shore wind potential could be deployed as base load power replacing coal-fired system with benefits not only in terms of reductions in CO2 emissions but also in terms of improvements in regional air quality. The interconnection of off-shore wind resources contemplated here could be facilitated by China's 12th-five-year plan to strengthen inter-connections between regional electric-power grids.

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