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Satellites See That Climate Change Has Caused A Greener Earth
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By rickyjames, Section News
Posted on Thu Jun 5th, 2003 at 03:24:58 PM EST
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Between 1982 and 1999, Earth's climate became warmer, wetter, and sunnier in many parts of the world. As the climate changed, plants found it easier to grow, producing changes that could be seen by satellites. These satellite observations of "Net Primary Productivity" (NPP)
reveal the seasonal and yearly cycles of Earth's vegetation. NPP is the difference
between the CO2 absorbed by plants during photosynthesis and CO2 lost by
plants during respiration. NPP is the foundation for food, fiber, and fuel
derived from plants, without which life on Earth could not exist. Humans
appropriate approximately 50 percent of global NPP. NPP globally increased
on average by 6% from 1982 to 1999; the Earth's carbon dioxide levels increased
9% during this time.
Researcher Ramakrishna Nemani and colleagues present in this week's Science
a global map of the NPP of plants from climate and satellite data of vegetation
greenness and solar radiation absorption. Ecosystems in tropical zones and
in the high latitudes of the Northern Hemisphere accounted for 80 percent
of the increase. NPP increased significantly over 25 percent of the global
vegetated area but decreased over seven percent of the area. This illustrates
how plants respond differently depending on regional climatic conditions.
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proposes climatic changes as the leading cause for the increases in plant
growth over the last two decades, with lesser contribution from carbon dioxide
fertilization and forest re-growth," said Nemani. No one knows whether these
positive impacts are due to short-term climate cycles or longer-term global
climate changes. Also, a 36 percent increase in global population, from 4.45
billion in 1980 to 6.08 billion in 2000, overshadows the increases in plant
growth.
NASA satellites continue to measure global changes
in NPP and will provide scientists with a strong platform for understanding
changes in Earth's systems in years and decades to come. The measurements
are made using the Advanced Very High Resolution Radiometers on NOAA TIROS-N satellites.
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