- Researchers have found that the variations
in the energy given off from the sun effect the Earth's wind patterns and
thus the climate of the planet, according to results of a new study published
in the April 9 issue of Science.
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- For decades, scientists have tried to
understand the link between winds and temperature and the sun and its cycles.
There were tell-tale signs of a connection. For instance, the Little Ice
Age recorded in Europe between 1550 and 1700 happened during a time of
very low solar activity. But how the sun and climate were linked continued
to elude researchers.
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- According to Drew Shindell, a climate
researcher from NASA's Goddard Institute for Space Studies in New York,
NY, and lead author of the new study, a key piece of the puzzle was missing.
Previous studies neglected to take into account the effects of increased
solar activity on the ozone layer or the complex chemistry of the upper
atmosphere where most of the high-energy radiation, including ultra-violet
radiation (the kind responsible for creating the ozone layer) gets absorbed.
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- "When we added the upper atmosphere's
chemistry into our climate model, we found that during a solar maximum
major climate changes occur in North America." The changes, according
to Shindell, are caused by stronger westerly winds. Changes also occur
in wind speeds and directions all over the Earth's surface.
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- "Solar variability changes the distribution
of energy," said Shindell. "Over an 11-year solar cycle, the
total amount of energy has not changed very much. But where the energy
goes changes as wind speeds and directions change." During the sun's
11-year cycle, from a solar maximum to a solar minimum, the energy released
by the sun changes by only about a tenth of a percent.
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- When the solar cycle is at a maximum,
it puts out a larger percentage of high-energy radiation, which increases
the amount of ozone in the upper atmosphere. The increased ozone warms
the upper atmosphere and the warm air affects winds all the way from the
stratosphere (that region of the atmosphere that extends from about 6 to
30 miles high) to the Earth's surface. "The change in wind strength
and direction creates different climate patterns around the globe,"
said Shindell.
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- According to Shindell, the new study
also confirms that changing levels of energy from the sun are not a major
cause of global warming.
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- Many scientists have argued that the
radiation change in a solar cycle - an increase of two to three tenths
of a percent over the 20th century - are not strong enough to account for
the observed surface temperature increases. The GISS model agrees that
the solar increases do not have the ability to cause large global temperature
increases, leading Shindell to conclude that greenhouse gasses are indeed
playing the dominant role.
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- The general circulation model used in
the study included solar radiation data from NASA's Upper Atmospheric Research
Satellite, launched in 1991. With data from UARS, which was used to calculate
ozone changes, scientists have good measurements of how much radiation
the sun puts out, increasing the accuracy of the new model.
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- ___________
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- Note: This story has been adapted from
a news release issued by NASA/Goddard Spaceflight Center for journalists
and other members of the public. If you wish to quote from any part of
this story, please credit NASA/Goddard Spaceflight Center as the original
source.
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