<P> In 1999 the contribution of civil aircraft - in - flight to global CO emissions was estimated to be around 2 % . However , in the case of high - altitude airliners which frequently fly near or in the stratosphere , non-CO altitude - sensitive effects may increase the total impact on anthropogenic ( human - made ) climate change significantly . A 2007 report from Environmental Change Institute / Oxford University posits a range closer to 4 percent cumulative effect . Subsonic aircraft - in - flight contribute to climate change in four ways : </P>
what percentage of global man-made co2 emissions comes from worldwide aviation
4 percent cumulative effect