NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the task group responsible for the report were chosen for their special competences and with regard for appropriate balance.

This study was supported by Contract NASW-01001 between the National Academy of Sciences and the National Aeronautics and Space Administration, with technical participation by the National Oceanic and Atmospheric Administration. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.

Cover: This image of Earth is a compilation of several data sets produced by NASA’s Earth Observing System and includes cloud cover, vegetation, fires, and sea-surface temperature. From the data set for sea-surface temperature, the 1997-1998 El Niño is clearly visible. SOURCE: Courtesy of R.B. Husar, Washington University.

Copies of this report are available free of charge from:

Space Studies Board

National Research Council

The Keck Center of the National Academies

500 Fifth Street, N.W.

Washington, DC 20001