# Air Pollution, Greenhouse Gases & Climate

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.
2007. Clearing the air: The health and economic damages of air pollution in China. Cambridge, MA: MIT Press. Publisher's VersionAbstract

An interdisciplinary, quantitative assessment of the health and economic costs of air pollution in China, and of market-based policies to build environmental protection into economic development.

China's historic economic expansion is driven by fossil fuels, which increase its emissions of both local air pollutants and greenhouse gases dramatically. Clearing the Air is an innovative, quantitative examination of the national damage caused by China's degraded air quality, conducted in a pathbreaking, interdisciplinary U.S.-China collaboration. Its damage estimates are allocated by sector, making it possible for the first time to judge whether, for instance, power generation, transportation, or an unexpected source such as cement production causes the greatest environmental harm. Such objective analyses can reset policy priorities.

Clearing the Air uses this information to show how appropriate "green" taxes might not only reduce emissions and health damages but even enhance China's economic growth. It also shows to what extent these same policies could limit greenhouse gases, suggesting that wealthier nations have a responsibility to help China build environmental protection into its growth.

Clearing the Air is written for diverse readers, providing a bridge from underlying research to policy implications, with easily accessible overviews of issues and summaries of the findings for nonspecialists and policymakers followed by more specialized, interlinked studies of primary interest to scholars. Taken together, these analyses offer a uniquely integrated assessment that supports the book's economic and policy recommendations.

Michael B. McElroy. 1998. “Industrial growth, air pollution and environmental damage: Complex challenges for China.” In Energizing China: Reconciling Environmental Protection and Economic Growth, edited by Michael B. McElroy, Chris P. Nielsen, and Peter Lydon. Cambridge, MA: HUCE/Harvard University Press. Publisher's VersionAbstract

As China develops its booming, fossil fuel-powered economy, is it taking lessons from the history of Western industrialization and the unforeseen environmental harms that accompanied it? Given the risks of climate change, is there an imperative, shared responsibility to help China respond to the environmental effects of its coal dependence? By linking global hazards to local air pollution concerns—from indoor stove smoke to burgeoning ground-level ozone—this volume of eighteen studies seeks integrated strategies to address simultaneously a range of harmful emissions. Counterbalancing the scientific inquiry are key chapters on China’s unique legal, institutional, political, and cultural factors in effective pollution control.

Energizing China, the stage-setting publication of an ongoing program of Harvard–China research collaboration, is distinguished by its conceptual breadth and spirit of exchange. Its contributors include twenty-two Western and seventeen Chinese scholars with a disciplinary reach that includes science, public health, engineering, economics, public policy, law, business, and China studies.

Chris P Nielsen, Mun S Ho, Jing Cao, Yu Lei, Yuxuan Wang, and Yu Zhao. 2013. “Summary: Carbon Taxes for 2013-2020.” In Clearer Skies Over China: Reconciling Air Quality, Climate, and Economic Goals, Pp. 103-157. 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. Y. Zhao, LP Qiu, RY Xu, FJ Xie, Q. Zhang, YY Yu, C.P. Nielsen, HX Qin, H.K. Wang, XC Wu, WQ Li, and J. Zhang. 2015. “Advantages of city-scale emission inventory for urban air quality research and policy: the case of Nanjing, a typical industrial city in the Yangtze River Delta, China.” Atmospheric Chemistry and Physics, 15, Pp. 12623-12644. Publisher's VersionAbstract With most eastern Chinese cities facing major air quality challenges, there is a strong need for city-scale emission inventories for use in both chemical transport modeling and the development of pollution control policies. In this paper, a high-resolution emission inventory of air pollutants and CO2 for Nanjing, a typical large city in the Yangtze River Delta, is developed incorporating the best available information on local sources. Emission factors and activity data at the unit or facility level are collected and compiled using a thorough onsite survey of major sources. Over 900 individual plants, which account for 97% of the city's total coal consumption, are identified as point sources, and all of the emission-related parameters including combustion technology, fuel quality, and removal efficiency of air pollution control devices (APCD) are analyzed. New data-collection approaches including continuous emission monitoring systems and real-time monitoring of traffic flows are employed to improve spatiotemporal distribution of emissions. Despite fast growth of energy consumption between 2010 and 2012, relatively small inter-annual changes in emissions are found for most air pollutants during this period, attributed mainly to benefits of growing APCD deployment and the comparatively strong and improving regulatory oversight of the large point sources that dominate the levels and spatial distributions of Nanjing emissions overall. The improvement of this city-level emission inventory is indicated by comparisons with observations and other inventories at larger spatial scale. Relatively good spatial correlations are found for SO2, NOX, and CO between the city-scale emission estimates and concentrations at 9 state-opertated monitoring sites (R = 0.58, 0.46, and 0.61, respectively). The emission ratios of specific pollutants including BC to CO, OC to EC, and CO2 to CO compare well to top-down constraints from ground observations. The inter-annual variability and spatial distribution of NOX emissions are consistent with NO2 vertical column density measured by the Ozone Monitoring Instrument (OMI). In particular, the Nanjing city-scale emission inventory correlates better with satellite observations than the downscaled Multi-resolution Emission Inventory for China (MEIC) does when emissions from power plants are excluded. This indicates improvement in emission estimation for sectors other than power generation, notably industry and transportation. High-resolution emission inventory may also provide a basis to consider the quality of instrumental observations. To further improve emission estimation and evaluation, more measurements of both emission factors and ambient levels of given pollutants are suggested; the uncertainties of emission inventories at city scale should also be fully quantified and compared with those at national scale. Xi Lu, Jackson Salovaara, and Michael B. McElroy. 2012. “Implications of the recent reductions in natural gas prices for emissions of CO2 from the US power sector.” Environmental Science & Technology, 46, 5, Pp. 3014–3021. Publisher's VersionAbstract CO2 emissions from the US power sector decreased by 8.76% in 2009 relative to 2008 contributing to a decrease over this period of 6.59% in overall US emissions of greenhouse gases. An econometric model, tuned to data reported for regional generation of US electricity, is used to diagnose factors responsible for the 2009 decrease. More than half of the reduction is attributed to a shift from generation of power using coal to gas driven by a recent decrease in gas prices in response to the increase in production from shale. An important result of the model is that, when the cost differential for generation using gas rather than coal falls below 2–3 cents/kWh, less efficient coal fired plants are displaced by more efficient natural gas combined cycle (NGCC) generation alternatives. Costs for generation using NGCC decreased by close to 4 cents/kWh in 2009 relative to 2008 ensuring that generation of electricity using gas was competitive with coal in 2009 in contrast to the situation in 2008 when gas prices were much higher. A modest price on carbon could contribute to additional switching from coal to gas with further savings in CO2 emissions. 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.; click here (http://news.harvard.edu/gazette/story/2012/02/model-situation/) to see coverage in the Harvard Gazette. 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. Ying Zhou, Jonathan I Levy, James K Hammitt, and John S Evans. 2007. “Population exposure to pollutants from the electric power sector using CALPUFF.” In Clearing the air: The health and economic damages of air pollution in China, edited by Mun S Ho and Chris P Nielsen. Cambridge, MA: MIT Press. Publisher's VersionAbstract An interdisciplinary, quantitative assessment of the health and economic costs of air pollution in China, and of market-based policies to build environmental protection into economic development. China's historic economic expansion is driven by fossil fuels, which increase its emissions of both local air pollutants and greenhouse gases dramatically. Clearing the Air is an innovative, quantitative examination of the national damage caused by China's degraded air quality, conducted in a pathbreaking, interdisciplinary U.S.-China collaboration. Its damage estimates are allocated by sector, making it possible for the first time to judge whether, for instance, power generation, transportation, or an unexpected source such as cement production causes the greatest environmental harm. Such objective analyses can reset policy priorities. Clearing the Air uses this information to show how appropriate "green" taxes might not only reduce emissions and health damages but even enhance China's economic growth. It also shows to what extent these same policies could limit greenhouse gases, suggesting that wealthier nations have a responsibility to help China build environmental protection into its growth. Clearing the Air is written for diverse readers, providing a bridge from underlying research to policy implications, with easily accessible overviews of issues and summaries of the findings for nonspecialists and policymakers followed by more specialized, interlinked studies of primary interest to scholars. Taken together, these analyses offer a uniquely integrated assessment that supports the book's economic and policy recommendations. Y. Zhou, Jonathan I Levy, James K Hammitt, and John S Evans. 2003. “Estimating population exposure to power plant emissions using CALPUFF: A case study in Beijing, China.” Atmospheric Environment, 37, 6, Pp. 815-826. Publisher's VersionAbstract Epidemiological studies have shown a significant association between ambient particulate matter (PM) exposures and increased mortality and morbidity risk. Power plants are significant emitters of precursor gases of fine particulate matter. To evaluate the public health risk posed by power plants, it is necessary to evaluate population exposure to different pollutants. The concept of intake fraction (the fraction of a pollutant emitted that is eventually inhaled or ingested by a population) has been proposed to provide a simple summary measure of the relationship between emissions and exposure. Currently available intake fraction estimates from developing countries used models that look only at the near field impacts, which may not capture the full impact of a pollution source. This case study demonstrated how the intake fraction of power plant emissions in China can be calculated using a detailed long-range atmospheric dispersion model—CALPUFF. We found that the intake fraction of primary fine particles is roughly on the order of 10−5, while the intake fractions of sulfur dioxide, sulfate and nitrate are on the order of 10−6. These estimates are an order of magnitude higher than the US estimates. We also tested how sensitive the results were to key assumptions within the model. The size distribution of primary particles has a large impact on the intake fraction for primary particles while the background ammonia concentration is an important factor influencing the intake fraction of nitrate. The background ozone concentration has a moderate impact on the intake fraction of sulfate and nitrate. Our analysis shows that this approach is applicable to a developing country and it provides reasonable population exposure estimates. Yu Zhao, Hui Zhong, Jie Zhang, and Chris P Nielsen. 2015. “Evaluating the effects of China's pollution control on inter-annual trends and uncertainties of atmospheric mercury emissions.” Atmospheric Chemistry and Physics, 15, Pp. 4317–4337. Publisher's VersionAbstract China's atmospheric mercury (Hg) emissions of anthropogenic origin have been effectively restrained through the national policy of air pollution control. Improved methods based on available field measurements are developed to quantify the benefits of Hg abatement through various emission control measures. Those measures include increased use of flue gas desulfurization (FGD) and selective catalyst reduction (SCR) systems for power sector, precalciners with fabric filter (FF) for cement production, machinery coking with electrostatic precipitator (ESP) for iron and steel production, and advanced manufacturing technologies for nonferrous metal smelting. Declining trends in emissions factors for those sources are revealed, leading to a much slower growth of national total Hg emissions than that of energy and economy, from 679 in 2005 to 750 metric tons (t) in 2012. In particular, nearly half of emissions from the above-mentioned four types of sources are expected to be reduced in 2012, attributed to expansion of technologies with high energy efficiencies and air pollutant removal rates after 2005. The speciation of Hg emissions keeps stable for recent years, with the mass fractions of around 55, 39 and 6% for Hg0, Hg2+ and Hgp, respectively. The lower estimate of Hg emissions than previous inventories is supported by limited chemistry simulation work, but middle-to-long term observation on ambient Hg levels is further needed to justify the inter-annual trends of estimated Hg emissions. With improved implementation of emission controls and energy saving, 23% reduction in annual Hg emissions for the most optimistic case in 2030 is expected compared to 2012, with total emissions below 600 t. While Hg emissions are evaluated to be gradually constrained, increased uncertainties are quantified with Monte-Carlo simulation for recent years, particularly for power and certain industrial sources. The uncertainty of Hg emissions from coal-fired power plants, as an example, increased from −48 ~ +73% in 2005 to −50 ~ +89% in 2012 (expressed as 95% confidence interval). This is attributed mainly to swiftly increased penetration of advanced manufacturing and pollutant control technologies. The unclear operation status or relatively small sample size of field measurements on those technologies results in lower but highly varied emission factors. To further confirm the benefits of pollution control polices with reduced uncertainty, therefore, systematic investigations are recommended specific for Hg pollution sources, and the variability of temporal trends and spatial distributions of Hg emissions need to be better tracked for the country under dramatic changes in economy, energy and air pollution status. 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. Chris P Nielsen and Mun S Ho. 2007. “Air pollution and health damages in China: An introduction and review.” In Clearing the air: The health and economic damages of air pollution in China, edited by Chris P Nielsen and Mun S Ho. Cambridge, MA: MIT Press. Publisher's VersionAbstract An interdisciplinary, quantitative assessment of the health and economic costs of air pollution in China, and of market-based policies to build environmental protection into economic development. China's historic economic expansion is driven by fossil fuels, which increase its emissions of both local air pollutants and greenhouse gases dramatically. Clearing the Air is an innovative, quantitative examination of the national damage caused by China's degraded air quality, conducted in a pathbreaking, interdisciplinary U.S.-China collaboration. Its damage estimates are allocated by sector, making it possible for the first time to judge whether, for instance, power generation, transportation, or an unexpected source such as cement production causes the greatest environmental harm. Such objective analyses can reset policy priorities. Clearing the Air uses this information to show how appropriate "green" taxes might not only reduce emissions and health damages but even enhance China's economic growth. It also shows to what extent these same policies could limit greenhouse gases, suggesting that wealthier nations have a responsibility to help China build environmental protection into its growth. Clearing the Air is written for diverse readers, providing a bridge from underlying research to policy implications, with easily accessible overviews of issues and summaries of the findings for nonspecialists and policymakers followed by more specialized, interlinked studies of primary interest to scholars. Taken together, these analyses offer a uniquely integrated assessment that supports the book's economic and policy recommendations. 1998. Energizing China: Reconciling Environmental Protection and Economic Growth. Cambridge, MA: HUCE/Harvard University Press. Publisher's VersionAbstract As China develops its booming, fossil fuel-powered economy, is it taking lessons from the history of Western industrialization and the unforeseen environmental harms that accompanied it? Given the risks of climate change, is there an imperative, shared responsibility to help China respond to the environmental effects of its coal dependence? By linking global hazards to local air pollution concerns—from indoor stove smoke to burgeoning ground-level ozone—this volume of eighteen studies seeks integrated strategies to address simultaneously a range of harmful emissions. Counterbalancing the scientific inquiry are key chapters on China’s unique legal, institutional, political, and cultural factors in effective pollution control. Energizing China, the stage-setting publication of an ongoing program of Harvard–China research collaboration, is distinguished by its conceptual breadth and spirit of exchange. Its contributors include twenty-two Western and seventeen Chinese scholars with a disciplinary reach that includes science, public health, engineering, economics, public policy, law, business, and China studies. Yu Lei, Qiang Zhang, Chris P Nielsen, and Kebin He. 2013. “Primary Air Pollutants and CO2 Emissions from Cement Production in China.” In Clearer Skies Over China: Reconciling Air Quality, Climate, and Economic Goals, Pp. 203-224. 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.