Carmichael discussed an integrated assessment of expanding energy use in Asia on the environment. The first phase of this project, funded by the World Bank and the Asian Development Bank, is now complete. The model was developed by a team that included energy experts, atmospheric modelers, environmental assessors, policy analysts, and others concerned about impacts of the 5-15% growth in energy consumption in Asian countries. Three quarters of all new electric power plants planned globally for the 1990s are being built in Asia.

This assessment was restricted to sulfur emissions and includes the effects of sulfate aerosols on climate, impacts of sulfur deposition on ecosystems, including agriculture, and the human health effects of sulfur dioxide emissions. The region studied stretched from Pakistan to Japan and from Mongolia to Indonesia. The preliminary integrated assessment follows from three major areas: 1) energy supply and demand scenarios which generate emissions at 1 degree resolution, 2) a long range transport model to calculate sulfur deposition and ambient levels of sulfur dioxide and sulfate, and 3) an ecosystem assessment using sensitivities and "critical loads" concepts as developed in Europe for the acid rain conventions and protocols.

Base year emissions were estimated for 1990 and forecasts were made over a 30 year time horizon for 2000, 2010, and 2020. The model provides a framework for large databases in a PC-based environment that makes this data available to everyone in the region to use in their own studies. This sharing of data is a strong component of the project. For each of the three areas (energy, atmospheric transport and deposition, and ecosystem analysis) there were western investigators and focal centers set up in various locations in Asia. Scientists from each Asian country participated and provided feedback throughout the process, making it an interactive one. A peer evaluation of the preliminary results was completed in May 1995.

For the purposes of this model, Asia was divided into 94 regions, and 20 megacities were identified and studied. Energy and technology implementation scenarios were run in each region and megacity independently. Asia is such a dynamic region that a platform for dynamic analysis was necessary. This model provides such a platform.

The base year inventory for China is estimated at 22 terragrams of SO₂ emission in China for 1990. From this base year, a number of scenarios were run from business-as-usual through best available technology implementation. China currently accounts for 65% of Asia's emissions and projections for a business-as-usual scenario show China's output tripling, India's rising by a factor of four, and Pakistan's by a factor of ten. Control technologies at various levels of implementation can also be brought into the mix.

Four hundred large point sources are placed in the model. These include existing stacks plus those planned for the next 20 years. The model can be run to bring more or fewer of these on line depending on various policy decisions, and can also be used to evaluate alternative sites for plants. Volcanic emissions account for about 3 Tg per year and these are included in the model. Ship emissions are also included and account for about 0.25 Tg of sulfur. While this appears to be a small amount in the aggregate, in certain areas such as the Malocan Straits, this accounts for 20% of total.

Once the energy scenarios have generated the 1° by 1° emissions, the atmospheric transport part of the model comes into play, helping to determine where the emissions go and how much sulfur is deposited in what locations.

The long range transport model used is a 3-layer trajectory model. Sulfur deposition patterns closely reflect the spatial variability in the emissions patterns and the prevailing meteorology. Elevated levels of sulfur deposition occur in the central regions of India, Thailand, eastern China, Korea, and parts of Malaysia and Indonesia. The highest levels (about 10g S.m^-2.yr^-1) occur in the Sichuan-Chong Qing region of China. The model also tracks each source individually so that source-receptor information can be assessed. In east Asia, the winds are predominantly westerly, so that pollutants are transported off the continent into the Pacific Ocean (see Liu). How much of the deposition in Korea and Japan is from long range transport is an open question. If it is found, for example, that Japan would be heavily impacted by sulfur from Chinese coal burning, this could encourage Japan to invest in Chinese energy technology.

Once the transport model has determined the amount and location of deposition, the final element of the model is used to examine ecosystem response. This large mapping project takes into account vegetation sensitivity to sulfur and more importantly, how soil chemistry responds to sulfur deposition. The concept, borrowed from European acid rain work, is called "critical loads," and is a method of estimating ecosystem sensitivity to sulfur deposition. It is essentially a threshold sustainability index of ecosystems to sulfur deposition and is estimated for various soil and vegetation types and land uses.

The concept behind critical loads is that some soils can sustain much higher levels of deposition than others. Because of this differential sensitivity, different ecosystems are placed at risk of damage at differing levels of deposition. For example, the high pH soils in Northern China have a large capacity for sustaining sulfur deposition. By overlaying a sulfur deposition map with a critical loads map, we can see the areas at risk. For 1990, this project showed large exceedances in southeastern and coastal regions in northern China, Thailand, Malocan Straits, and a few other locations. This process identifies "red flag" areas that should be studied more closely.

In the analysis described above, "risk" is defined as changes in soil chemistry and toxicity to vegetation that might result from the mobilization of aluminum and other chemicals in the soil. It is important to point out that there are very large uncertainties in applying these concepts. The concept of critical loads is still debatable and controversial, but provides a valuable framework for evaluating environmental impacts.

Another use of the model is to look at human health and agricultural impacts by zooming in with higher resolution. Around and downwind of Beijing, for example, it was found that there were large regions where the average concentration exceeded 80 micrograms of SO₂ per cubic meter and short term average concentrations of 350 µg .m^-3. These numbers can be compared with the World Health Organization's annual exposure standard of 50 µg.m^-3and 24-hour exposure standard of 125 µg .m^-3. In addition, vegetation can be adversely affected at levels of 25 µg m^-3.

In sum, the benefit of this model is that it is a framework that organizes large datasets in a PC environment that allows for dynamic, policy-relevant studies of the region. For example, if a power plant was moved to a different location, what might happen to the sulfur deposition pattern? The usefulness of these types of maps is that they reveal the gradients. They provide a scoping type of evaluation that indicates where to look first for problems.

There is also a great deal of value in scoping future scenarios for SO₂ in Asia. Figure 1.1 shows the effects of four scenarios in the future. As the graph demonstrates, a business-as-usual scenario with no further control technologies used results in emissions rising by a factor of 3. Use of basic technology (characterized by low capital investment and multiple benefits) results in emissions rising by a factor of 2. Immediately applying the best available technology on a large scale basis could perhaps stabilize emissions at 1990 levels. For China, the costs of this last scenario are estimated to require an annual investment of $100 billion a year in power generation, home heating, and largest of all, industrial processes.

Phase two of this assessment project is expected to be funded by the World Bank and will involve a great deal of ground truthing and case studies. It is also hoped that a variety of users will work with and modify the model for a number of different uses.