Climate change, weather extremes, atmospheric pollution, and
space weather have significant societal, environmental, and
economic costs. More accurate prediction can help reduce these
costs by providing advance warning of dangerous conditions. But
the development of effective long-term strategies to minimize
damages is hampered by incomplete ability to attribute observed
changes in the atmosphere and Earth system to specific causes
and mechanisms. For instance, the precise mix of factors driving
regional climate variability is not fully understood. There are
also many unanswered questions about the relationships among
atmospheric change and ecological, biological, and societal
processes. Improved understanding of such relationships would,
for example, enable us to better anticipate how continued
climate change will affect water availability, agriculture, and
urban development in the western United States or to project the
rate of loss of biodiversity from the combination of climate
change, degraded air qualit