If you really want to understand how the Earth's climate works,
you may have to leave the planet
By Curt Suplee
April 20, 2000
That's precisely what NASA and its international collaborators have done by placing a new $1.3 billion satellite named Terra in a 438-mile-high polar orbit. Launched in December, the 11,442-pound spacecraft has just completed shakedown tests on its five suites of high-tech instruments, and has begun to collect data that scientists hope will provide desperately needed understanding of the way land, sea and air interact with each other and with clouds, vegetation and airborne compounds to influence global climate. Terra marks the beginning of a "new era" that "will help us examine practically every aspect of our changing world from space," Ghassem Asrar, NASA's associate administrator for the Office of Earth Sciences, said yesterday at agency headquarters.
The United States launched its first Earth-observing satellite 40 years ago, and many satellites now study various aspects of the Earth's surface, from plant diversity to urban sprawl to sea levels. But none was specifically designed to answer the tough and hugely complex questions that global warming and climate science have posed. Among the more pressing:
* How much energy from the sun is absorbed, exchanged and reflected by different parts of the surface, different levels of the atmosphere, different kinds of clouds and different sorts of airborne compounds, both natural and artificial?
* What, exactly, becomes of the 6 or 7 billion tons of carbon (in the form of carbon dioxide from the burning of fossil fuels) that civilization dumps into the air every year?
* How does vegetation change as a function of human activity or cloud cover?
* And how do airborne sulfate aerosols--shiny byproducts of fossil fuel combustion--affect the amount of sunlight that penetrates the atmosphere?
The answers to those and many other questions are urgently needed to reduce the vexing uncertainty in computerized models used to project climate and global warming trends. The 22-foot-long satellite, bristling with sensors, is expected to address those problems on a daily basis and a global scale. It is "designed for a comprehensive check-up of planet Earth," said Terra project scientist Yoram Kaufman of Goddard Space Flight Center in Greenbelt, which manages the program. The instruments will collect approximately 1 trillion bytes of data per week, which will be distributed to about 1,000 participating scientists worldwide--and eventually to anyone else, including students. The first major science results will arrive within a year, NASA officials said.
In the long term, Terra will be joined by more than two dozen other satellites in NASA's Earth Observing System. The first, scheduled for launch later this year, will be a companion craft that, like Terra, will orbit the Earth 16 times a day, although on a different schedule. Terra's orbit carries it over the equator at about 10:30 a.m. local time, before billows of light-obscuring clouds form over the world's tropical land masses. Terra's detector array includes a Japanese instrument, ASTER, that can measure soil, vegetation and cloud properties at extremely high resolution, sampling areas as small as half a football field. Canada provided a device called MOPITT that will track lower-atmosphere concentrations of carbon monoxide and methane (a major greenhouse gas) for the first time from space.
The United States supplied an instrument called MODIS that monitors the entire globe daily in 36 wavelengths, the CERES detector that records the amount of light reflected from clouds as well as the amount of thermal energy radiated, and MISR, a multi-unit module that uses nine cameras, each of which views the same area at a different angle and in four different wavelengths. "Climate change is not only the greenhouse effect," Kaufman said. It involves numerous feedback processes among clouds, aerosols, water vapor and half a dozen other variables. "We really need to understand the whole system."
FAIR USE NOTICE: This page contains copyrighted material the use of which has not been specifically authorized by the copyright owner. Global Policy Forum distributes this material without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. We believe this constitutes a fair use of any such copyrighted material as provided for in 17 U.S.C íŸ 107. If you wish to use copyrighted material from this site for purposes of your own that go beyond fair use, you must obtain permission from the copyright owner.
