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Updated 12 October, 2003
Development of Asian Megacities: Environmental, Economic, Social, and Health Implications
USGCRP Seminar, 11 June 1998
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What are the current and projected trends in Asian megacities with respect to greenhouse gas emissions, ground-level ozone pollution, energy use, sulfur dioxide aerosols, and population in the next 20, 50, and 100 years? Should air pollution and climate change be treated as separate issues? How much of a risk does air pollution currently pose to human health in Asia? What are the prospects for the future? Are there an array of cost-effective options available to simultaneously address the issues of human-induced climate change and air pollution?


Dr. Jack A. Kaye
Manager, Atmospheric Chemistry Modeling and Analysis Program, Office of Earth Science, National Aeronautics and Space Administration, Washington, DC


Dr. Gregory R. Carmichael
Department of Chemical and Biochemical Engineering, and Co-Director of the Center for Global & Regional Environmental Research, University of Iowa, Iowa City, IA

Dr. F. Sherwood Rowland
Recipient of the 1995 Nobel Prize in Chemistry, and the Donald Bren Research Professor of Chemistry and Earth System Science, University of California, Irvine, CA

Asia and, in particular, Asian megacities, are some of the most dynamic and diverse regions of the world. As the poorer regions strive to catch up to the more developed ones, the environment is often caught in the middle, and in some cases given cursory attention. Awareness is mounting of the need for cooperation at local, regional, and international levels in addressing many of Asia's environmental problems, because Asian development will have profound impacts on the environment, in Asia and well beyond. .

Fueled by high population growth and vibrant economies, energy consumption in Asia currently represents ~20% of the world total, and it is estimated that its share will grow to 30% by 2015. Because fossil fuels will provide much of this energy, emissions of greenhouse gases and air pollutants such as sulfur and nitrogen oxides and particulates are projected to dramatically increase. During 1990-1996, total energy-related carbon emissions in East Asia grew at an average rate of 4.5% per year compared to the world average of 0.6% per year. Over the last two decades, China's SO2 (sulfur dioxide) emissions have grown by more than a factor of three, and this trend is expected to continue, with Asia-wide emissions projected to increase by another factor of two to three between now and 2020.

Asian Development and the Environment

The impacts of Asia's growth in emissions will have wide-ranging consequences. Acid precipitation is an illustrative example. China's National Environmental Protection Agency (NEPA) recently released a report indicating that economic losses due to acid rain damage to forests and farmland are now estimated at $13.25 billion annually, five times higher than initially assessed in 1996. The long range transport and fate of pollutants away from Asia is an area of increasing scientific interest and political concern because countries are receiving increasing amounts of pollutants from neighboring and even distant countries. The recent episodes of severe smoke and haze throughout Southeast Asia underscore this point.

Another key dynamic in Asia is the urban environment. As subsistence workers migrate from rural areas to the cities seeking relief, urban populations are growing faster than the national averages. Asia presently has ~1 billion urban dwellers, and this number is expected to rise to nearly 3 billion in 2025. The ten megacities (populations greater than 10 million) will then account for ~40% of their country's GNP (gross national product). Though reliable monitoring and health effects data are lacking in many cases, indications are that damage to human health and well-being from poor air quality (both in and out of doors) is extensive. Without strong intervention the situation will inevitably worsen.

The emissions of chlorofluorocarbons and carbon dioxide contribute to well known global atmospheric problems. However, when local pollution problems are numerous enough, they can grow to create global problems. The increase in tropospheric ozone (low- or ground-level ozone) concentrations provides a particularly clear example of this globalization of pollution. The basic ingredients in the formation of ozone in the urban atmosphere are now well-established: partially-burned hydrocarbons, nitrogen oxides, and sunlight. The motorization of urban environments all around the world has produced local smog, including ground-level ozone, in hundreds of cities. Ozone formation continues in the urban plumes extending downwind from the cities in which emissions occur, until the components are diluted below critical concentration levels. However, when the dilution has not been completed by the time the plume enters the next city, the pollution is converted from a local problem into a regional problem. The growth in emissions in eastern Asia, in particular, has now advanced so that the regional problems are coalescing further into zonal problems affecting all locations within a particular latitude zone, e.g., between 25°N and 50°N latitudes. A similar zonal problem exists in the southern hemisphere, driven largely by the extensive burning there of forests and agricultural wastes.

While projections based on current growth and present environmental protection and practices paint a very pessimistic picture, the growth in emissions in Asia will most certainly not follow these projections. There has already been a (temporary) downturn in several of the “Tiger” economies (with the result that growth in regional carbon emissions may slow to 2% in 1998) and countries such as China are introducing experimental emission control systems and are beginning to establish regulations to more aggressively curb emissions of some pollutants. There are also ways to decouple energy growth from economic and population growth. Economic growth will not be equal across economic sectors, and the energy-intensive industrial sector is projected to grow less rapidly than the service sector, which has lighter energy demands. Growth in the transportation sector in Asia is very rapid, and, as a result, photochemical smog problems in Asian cities are on the rise. Without intervention the contribution of motor vehicles to energy use and emissions will rise dramatically.

Energy efficiency improvements are also important. In Asia, it is estimated that energy efficiency has the potential to reduce the growth in energy use and emissions in 2020 by 30%; even with these improvements in energy efficiency emissions will still double by the year 2020. Efficient, low-polluting technologies for the combustion of fossil fuels and for the treatment of effluent gases offer a substantial opportunity over the next 20 to 30 years to help meet the expanding energy needs and to help limit the environmental damage. The use of advanced control technologies, for example, could reduce the emissions of SO2 below current levels, albeit at high cost (~$90 billion annually).

The pressing environmental problems of urban pollution and climate change in Asia are closely linked problems sharing common causes and solutions. The fact that air pollution problems and greenhouse gas emissions arise largely from fossil fuel combustion and the important role of aerosols in both air pollution and climate change are illustrative examples. In Asia, it will be particularly important to develop energy/emissions policies which recognize the need for near-term benefits and that choices made in changing energy usage may have different climate change and health outcomes. In the urban environments of Asia, efforts to reduce emissions and to use less energy can have significant health benefits at rather low per capita costs ($10 to $50 per person protected). From a health perspective the benefits of a one-ton reduction in particulate emissions from household stoves are estimated to be at least 40 times greater than those from coal-fired power plants. Furthermore, shifting from coal-fired power plants to natural gas has larger health benefits than climate benefits, while shifting from coal power to hydroelectric results in the same percentage reduction in health effects and greenhouse gas emissions reductions.

There are a variety of steps that can be taken to help reduce the environmental impacts of Asian development. While no single action will be sufficient, the diversity of Asia offers substantial potential for improvement by focusing strategies on specific fuels, technologies, economic sectors, emission sources and ecologically sensitive ecosystems. The expansion and replacement of the energy infrastructure that will be required to meet projected Asian development also offers great opportunities to implement these strategies. The differences in cost-effective emission reductions in Asia (e.g., $3,600 per ton of SO2 reduced in Japan and $400-$500 per ton in China) also offer a mechanism for the region as a whole, for coordinating emission control strategies.


Dr. Gregory R. Carmichael is a professor in the Department of Chemical & Biochemical Engineering, and Co-Director of the Center for Global & Regional Environmental Research, at the University of Iowa. His main interests are the development and application of models for the analysis of long-range transport of acidic and photochemical pollutants on urban, regional and global scales. He has worked extensively on issues of long range transport of pollutants in Asia, and the impact of Asia development on the environment. He has received support for his work in Asia from the National Science Foundation (NSF), NASA, NOAA (Global Change Program), DOE, The World Bank, and the Asian Development Bank. Dr. Carmichael has over 120 refereed journal publications, serves on numerous editorial boards, is past chair of the American Meteorological Society's Committee on Atmospheric Chemistry, and serves as a consultant to the World Meteorological Organization (WMO) on issues related to Asia. He is presently working with WMO on issues related to the recent Indonesian forest fires and acid deposition.

Dr. F. Sherwood Rowland is the Donald Bren Research Professor of Chemistry at the University of California at Irvine, where he arrived in 1964 as the first chair of the Department of Chemistry. Since 1994, Dr. Rowland has also been serving as the elected Foreign Secretary of the National Academy of Sciences. Prior to his arrival at UC-Irvine, Dr. Rowland had held faculty positions at Princeton University and the University of Kansas. He earned his bachelor's degree from Ohio Wesleyan University and his master's and doctoral degrees from the University of Chicago. More than 50 scientists have received Ph.D. degrees under his direction. Dr. Rowland's research specialty is atmospheric chemistry and radiochemistry. With colleague Dr. Mario Molina, he was the first scientist to warn that chlorofluorocarbons released into the atmosphere were depleting the Earth's stratospheric ozone layer. Research on CFCs and stratospheric ozone eventually led, in 1987, to the United Nations Montreal Protocol, the first international agreement for controlling and ameliorating environmental damage to the global atmosphere. The terms of the Montreal Protocol were later strengthened in 1992 to attain a complete phaseout of further CFC production by the year 1996. Dr. Rowland has also been investigating the impact of methane gas (CH4) on the atmosphere. Methane is another potent greenhouse gas whose atmospheric concentration has doubled in the past two centuries. Presently, Dr. Rowland's research group is investigating the hydrocarbon and halocarbon composition of the atmosphere both from aircraft in remote locations and on the surface in heavily polluted cities.

Dr. Rowland is a member of the National Academy of Sciences and the American Academy of Arts and Sciences. In 1983, he and Dr. Molina received both the Tyler World Prize in Ecology and Energy, and the Award for Creative Advances in Environmental Science and Technology of the American Chemical Society. In 1987, Dr. Rowland received the Charles A. Dana Award for Pioneering Achievements in Health, and in 1988, he was made a member of the Global 500, the Honor Roll of the United Nations Environment Programme. In 1989, he received the Japan Prize in Environmental Science and Technology, and in 1994 he received the Albert Einstein Prize of the World Cultural Council. From 1991-1993, he served successive one-year terms as President-Elect, President, and Chairman of the Board of the American Association for the Advancement of Science. In 1993 Dr. Rowland was awarded the American Chemical Society's Peter Debye Medal in Physical Chemistry, and in 1994, he was awarded the Roger Revelle Medal of the American Geophysical Union. In 1995, he shared the Nobel Prize in Chemistry with Mario Molina and Paul Crutzen.


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