FIGURE 9.1 Sea ice minimums calculated using a 3-year moving average for the period 1979–1981 (left) and 2003–2005 (right). Satellites have made continual observations of Arctic sea ice extent since 1978, recording a general decline throughout that period. Since 2002, satellite records have revealed unusually early onsets of springtime melting in the areas north of Alaska and Siberia. In addition, the 2004–2005 winter season showed a smaller recovery of sea ice extent than any previous winter in the satellite record, and the earliest onset of melt throughout the Arctic SOURCE: NASA (2005). Courtesy of NASA.

implementing more comprehensive approaches to environmental study (NRC, 1999d). The first recommendation of the U.S. National Assessment of Climate Change Impacts (National Assessment Synthesis Team, 2000) calls for a more integrated approach to examining the impacts and vulnerabilities associated with multiple stresses (Figure 9.1). Several effects and vulnerabilities are particularly noteworthy. Changes in the volume of water stored on land as ice and snow are of critical importance to coastal populations and infrastructure because of the effects on sea level. Water resource management is strongly tied to climate and weather, and adaptation strategies are expensive and often require decades to implement. Climate change research has considerable potential to improve the anticipation of adverse health outcomes specifically related to heat mortality, changes in the pattern and character of vector-borne diseases, and air quality. Finally, climate change research is a major factor in improving the ability to be better stewards of natural ecosystems.

This vision recognizes that the demand for knowledge of climate change and variability will intensify. The objective is to improve the ability to anticipate the future and thus increase the capability to use the knowledge to limit adverse outcomes and maximize benefits to society. Failure to obtain that knowledge carries high risks.

OBSERVATIONAL NEEDS AND REQUIREMENTS

The Panel on Climate Variability and Change focused on four fundamental questions in its approach to specific space-based and supporting in situ and surface-based observations required for studies of Earth’s climate: What governs Earth’s climate? What forces climate change? What feedbacks affect climate vari-



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