for National Geographic News
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A buildup of carbon dioxide in Earth's atmosphere could require changes in the way satellites are launched and might impact the function of global positioning systems (GPS), an international team of atmospheric scientists suggests.
Networks of orbiting GPS satellites send signals back to Earth that allow everything from jetfighters to cell phones to pinpoint their exact locations.
The same carbon dioxide that is a prime culprit for global warming in Earth's lower atmosphere is also causing the upper atmosphere to cool and contract, the team reported in last week's issue of the journal Science.
This change will be both good and bad for the orbiters, Jan Lastovicka, lead study author and researcher at the Institute of Atmospheric Physics in Prague, Czech Republic, said in an email.
As the upper atmosphere pulls in closer to Earth, the air at altitudes where low-orbit satellites reside will be less dense, meaning the craft can more easily maintain orbit and therefore last longer, Lastovicka said.
But spacecraft—including those that deliver new satellites into orbit—currently jettison booster rockets and other debris at about the same altitude.
The craft drop debris at just the right height to ensure that it will fall back to Earth relatively quickly and burn up in the atmosphere.
"If the atmosphere contracts, there will be less atmosphere up there to get rid of all the junk," said study co-author John Emmert of the U.S. Naval Research Laboratory's E. O. Hulburt Center for Space Research in Washington, D.C.
As conditions continue to change, space agencies will need to reevaluate their launch procedures to avoid increased risk, he said.
Changes in the upper atmosphere could also affect radio signals being sent from GPS satellites.
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