tists, government laboratories, and research support facilities, could lead to significant improvements in our ability to make critical measurements in the atmosphere.
Human activity is having documented effects on the weather and climate. For example, carbon dioxide and sulfate concentrations in the atmosphere have been changed dramatically by human activity, and the effects of these changes are beginning to appear in the climate of the Earth. In some major cities, pollution advisories warning of hazards to health and leading to restrictions on activities are becoming increasingly common. Biomass burning by humans is the predominant source of particulates and of some chemicals in some regions, and perhaps worldwide. As the global population continues to increase and to industrialize, these problems will become more urgent.
Many of the components of the research program recommended here address sources of uncertainty in climate prediction. Other benefits will result from improved abilities to predict regional climate and weather. When policies to mitigate anthropogenic effects on climate and weather or to manage water and other natural resources are debated, the results of the research proposed here will provide the critical basis for making sound decisions. The difficult choices are likely to involve accepting damage to the economy or to health, penalizing developing or industrialized countries, and burdening current or future generations. In this context, the importance to society of the scientific information that accrues from the research recommended here is indisputable.