European Aviation Safety Agency

A new study by the EU's aviation regulator EASA has found that "aviation emissions are currently warming the climate at approximately three times the rate of that associated with aviation CO2 emissions alone."

This is due to non-CO2 emissions, which are harder to quantify and not well studied. The new study examined the impact of these emissions, including nitrogen oxide, water vapor, oxidized sulfur and soot particles.

About 2 percent of global CO2 emissions are caused by aviation, but that does not include the non-CO2 emissions listed above.