Earth Observations from Space: The First 50 Years of Scientific Achievements (2008)

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1 Introduction Over the past 50 years, the United States has devel- of understanding and managing natural resources over the oped impressive capabilities for observing Earth from coming decades. In addition to the decadal survey, NASA space-based platforms. Global observations of a wide range asked the National Academies to look back on the history of of geo­physical and biological parameters have provided space-based observations of Earth to illustrate the contribu- unprecedented insight into how the Earth system functions tions to the scientific enterprise to date (Box 1.1). and have led to many fundamental scientific advances. The capacity to forecast and project weather, climate, and envi- THE STUDY’S APPROACH ronmental hazards has benefited extensively from satellite- based Earth observations. Satellite observations have literally The committee relied on the relevant literature, its own transformed the way we view the planet. Earth observations collective experience, and input from the Earth science from space have provided the information needed to verify community to compile an extensive list of accomplishments and complete our understanding of how ozone chemistry in resulting from Earth observations from space. Using its the stratosphere controls the infamous polar ozone hole; how expert judgment, the committee chose a subsample of the ocean currents, temperatures, and atmospheric processes are major accomplishments that are compelling and illustra- coupled to the El Niño-Southern Oscillation; how snow cover tive to convey the extent to which satellite observations affects water cycle dynamics; and how numerous global and have revolutionized the way people view, understand, and regional factors influence sea level change. study Earth. The committee did not attempt to provide a The Earth science community is devoting significant comprehensive inventory of accomplishments resulting efforts to planning future observations and research to be from satellite information and recognizes the inherent bias conducted with space-based platforms. One important ele- of composing any selective list. Nevertheless, the commit- ment of this effort is the recent “decadal survey” led by the tee believes that any other group of Earth scientists would National Academies: Earth Science and Applications from have provided a compilation with considerable overlap with Space: Urgent Needs and Opportunities to Serve the Nation the one presented in this report, in part because committee (NRC 2005) and Earth Science and Applications from Space: members were selected with careful consideration to balanc- National Imperatives for the Next Decade and Beyond (NRC ing expertise. 2007a). These are two forward-looking reports funded jointly In addition to its own expertise, the committee invited by the National Aeronautics and Space Administration other experts to contribute in a variety of ways: the com- (NASA), U.S. Geological Survey, and National Oceanic and mittee invited presentations during a series of meetings, Atmospheric Administration (NOAA). The reports provide held a town hall session at the 2006 Annual Meeting of the guidance to the three agencies regarding future priorities and American Geophysical Union, posted a call for input on the briefly summarize the value of satellite observations to the committee’s website, and approached the following Earth well-being of society. However, the continued availability science communities with a solicitation for contributions on of environmental satellite data in the future is jeopardized accomplishments from Earth satellite observations: because of budgetary constraints and programmatic difficul- ties (NRC 2005, 2007a). Consequently, the reports recom- • members of the National Academy of Sciences and mend a renewal of the commitment to support observations National Academy of Engineering, from space in view of the scientific and societal challenges  

INTRODUCTION  BOX 1.1 Statement of Task This study documents specific scientific accomplishments resulting from the nation’s research and development of space-based Earth observational capabilities. The study committee sought broad community input to identify examples of important accomplishments, in part by drawing on the expertise of the various entities within the National Academies and also involving those scientific communities that develop and use remote sensing observations of the Earth. The study’s main objective is to document, using examples and explanation, how satellite observations uniquely contributed to scientific understanding of the atmosphere, ocean, land, biosphere, and cryosphere. As secondary ob- jectives, the study also addresses how satellite observations have contributed to the ability to predict variations in the Earth system (e.g., weather, climate variability, water availability, earthquakes, volcanoes, and tsunamis) and comments on opportunities to improve future Earth science research enabled by the vantage point of space. To the extent possible, the committee organizes its comments to correspond to NASA’s seven Earth science foci: (1) atmospheric composition; (2) carbon cycle and ecosystems; (3) climate variability and change; (4) earth surface and interior structure; (5) weather; (6) water and energy cycles; and (7) Sun-Earth connection. • members of relevant boards within the National major scientific accomplishments that have transformed and Academies, contributed to the Earth sciences. The committee considered • recipients of the quarterly newsletter of the National as major accomplishments only scientific advances that Academies’ Board on Atmospheric Sciences and Climate, resulted in a new discovery, transformative science, prov- and ing or disproving an important theory, opening new major • members of relevant scientific e-mail distribution research venues, or providing significant societal benefits. lists. These accomplishments are described in Chapters 3 to 11. In the final chapter (Chapter 12), the committee summarizes This report begins with a brief early history of the conclusions drawn from these major accomplishments and evolution of Earth observations from space (Chapter 2). In highlights opportunities to improve future Earth science subsequent chapters the committee presents examples of research enabled from the vantage point of space.