A build-up of carbon dioxide in the upper levels of the earth's atmosphere risks causing a faster accumulation of man-made space junk, which could cause more collisions, scientists warn.
While on earth it causes warming, CO2 conversely cools down the atmosphere and contracts its outermost layer - the thermosphere - where many satellites, including the International Space Station (ISS), operate, found a study published in the journal Nature Geoscience.
A contracted thermosphere, in turn, reduces atmospheric "drag" on satellites - a similar force to that experienced when holding one's hand out the window of a moving car.
This drag is what causes satellite orbits to change, drawing them closer to Earth, which means orbiters, such as the ISS, have to use on-board engines to boost themselves back on course.
"The observed CO 2 increase is expected to gradually result in a cooler, more contracted upper atmosphere and a consequent reduction in the atmospheric drag experienced by satellites," said the Naval Research Laboratory, which took part in the study.
Space expert Hugh Lewis said a cooler troposphere will extend the lifetime of space junk - staying farther out for longer instead of burning up lower in the atmosphere, closer to Earth.