Observations of the Earth

Towards Predicting Climate Change

As we transition to the 21st century, the Earth's environment will be the focus of many agricultural, industrial, societal, and political decisions. We recognize that we need more and better data to help us understand how current environmental change trends may impact climate years or even decades in the future. To collect these data, in 1991, NASA established the Earth Observing System (EOS) program in response to a U.S. Presidential initiative to provide in-depth scientific understanding about the functioning of the Earth as a system. The EOS charter is to collect, at a minimum, a new 15-year data set on which to base a long-term and comprehensive examination of our planet's climate system. EOS is a multi-national endeavor comprised of three parts: (1) a series of advanced satellite remote sensors; (2) a robust new computer network (called EOSDIS) for processing, storing, and distributing EOS data; and (3) about 850 scientists working in many nations and in many Earth science disciplines who will use these new data in their research.

CERES Longwave Flux

Already, NASA has launched four EOS spacecraft in the 1990s, including Landsat 7, QuikScat, ACRIMSAT, and the EOS flagship—Terra—that was launched in December 1999. There are 15 more EOS satellites scheduled to launch through the year 2003. Rather than focusing on individual disciplines, the data from these EOS satellites will be integrated into a more holistic study of the Earth that includes seven overarching themes:

  • Radiation, clouds, water vapor, precipitation, and atmospheric circulation;
  • Ocean circulation, productivity, and exchange with the atmosphere;
  • Tropospheric chemistry and greenhouse gases;
  • Land ecosystems and hydrology;
  • Snow, ice, and glacier extent;
  • Ozone and stratospheric chemistry; and
  • Volcanoes and climate effects of aerosol.

With EOS, for the first time ever for a major Earth observation program, the goals include freely sharing the resulting data with both scientists and civilian organizations alike. This treatment of data contrasts sharply with previous satellite missions for which public access to data was quite costly. In fact, some EOS data are being directly broadcast freely to anyone anywhere who has a compatible receiving station and the capacity to process and store such a huge flow of information. As its name suggests, EOS is a large-scale, long-term collaborative mission involving scientists in government agencies, academia, and industry from many nations.

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Space-based Observations of the Earth

A Space-based Perspective
Earth is a Dynamic Planet
From Observing to Measuring Changes on Earth
Towards Predicting Climate Change

Left: Thermal radiation emitted from the Earth's surface and clouds on March 1, 2000, as seen by the Clouds and Earth's Radiant Energy System (CERES) aboard the Terra spacecraft. CERES measures the balance of solar energy received by the Earth and the energy reflected and emitted back into space. Understanding the energy coming into and out of the Earth system is critical for assessing whether scientists' models of global climate change are making accurate predictions. One of the main goals of NASA's Earth Observing System is to monitor and predict global climate change. This image is a one-day "snapshot" of the Earth. Yellow and red pixels show where more longwave radiation (basically heat) is escaping to space, and blue and light blue pixels show lower values. White areas at the North Pole, along a swath over the Pacific Ocean, and in thin gaps at intervals along the equator indicate missing data. (Image courtesy CERES science team, NASA Langley Research Center)