Needed Science: What efforts are needed to develop a system of observations, emissions, and models to better understand and track these flows?
Our current understanding of the magnitude of intercontinental flows of air pollution is sufficient to conclude that such flows have a significant impact on environmental quality throughout the Northern Hemisphere and that coordinated international actions to mitigate these flows would yield significant environmental and public health benefits. However, our current ability to accurately and precisely quantify the contribution of intercontinental flows on air pollution concentrations or deposition at any given location or the effect of international emission controls on pollution levels and their environmental or public health impacts is limited. To be able to better quantify the impacts of intercontinental flows of air pollution and the effects of international controls, additional efforts are needed to improve the coverage and resolution of our observational systems, the accuracy and resolution of our emissions inventories and projections, the fidelity and performance of our models of chemistry and transport, and the scope and detail of our impact assessments. Moreover, we need to shift the goal of the science activity from simply developing knowledge to a goal of informing action.