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October - December 1997


IN THIS ISSUE

Dealing With Global Warming:
The Need for Long-Term Actions

[Abstract] [References]

Reducing Indoor Air Pollution and Saving Energy, Too
[Abstract] [References]

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Dealing With Global Warming: The Need for Long-Term Actions


I recent years, intense international negotiations have focused on how much each of the developed nations should limit their emissions of carbon dioxide (CO2). Now researchers in MIT's Joint Program on the Science and Policy of Global Change warn that setting such limits will not by itself be a sufficient response if the threat of global warming proves real. Analyses using their "Integrated Global System Model" suggest that even the toughest current proposal for limiting emissions from developed nations will reduce projected warming in 2100 by only about 20%. Further, the analyses show that developed countries alone cannot reduce emissions enough to stabilize atmospheric CO2 concentrations at levels now proposed as "safe." The rapidly growing emissions from developing nations must also be curbed. There are even more challenging tasks for the long-term future. First, we should develop "greenhouse-friendly" technologies that permit emissions reductions without threatening economic health. Second, we should design broad international climate agreements that can evolve over time and that address all issues, from sources and sinks of all greenhouse gases to emissions monitoring and enforcement. Finally, we should develop an international system that can, if necessary, transfer substantial funds to developing countries to support their emissions-control efforts. These long-term undertakings should be tackled with the same fervor that characterizes current negotiations on near-term emissions limits.


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Reducing Indoor Air Pollution and Saving Energy, Too


R esearchers in MIT's Building Technology Program and the Energy Laboratory are studying an approach to ventilation that is radically different from that now used in the United States and could both improve indoor air quality and save energy. While conventional ventilation systems mix large quantities of newly conditioned air into the air in a room, "displacement ventilation" systems prevent mixing by injecting limited amounts of air, slowly and near the floor. Pollutants and heat that are produced by people and equipment rise naturally to ceiling exhaust vents, and the fresh air rises into the breathing space. The difficulty is that the precise system specifications--air temperature, velocity, and so on--must be tailored to the space being ventilated or occupants may be uncomfortable. The MIT researchers are developing tools that can help. They have formulated a computer model that calculates how different system specifications affect airflows and heat and pollutant dispersion in a well-defined room. And they have built a full-size experimental room in which they can test the effects of different ventilation strategies in various situations (an office with two "people" in front of computers, a classroom with "students" behind desks). The model predictions and experimental results agree quite well, and both confirm that a well-designed displacement ventilation system can provide clean air and comfort and also reduce the amount of ventilation air that must be heated or cooled--now a major consumer of energy in commercial buildings.


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