The aviation sector is responsible for a small but growing proportion of global greenhouse gas emissions. Recently the industry has been put in the spotlight, and there is a push for technological and policy solutions to improve emissions performance. Over the past year, airlines, aircraft manufacturers, and governments have initiated significant actions to address the sector's contribution to climate change. Aircraft are responsible for around three percent of global carbon dioxide emissions. But emissions of nitrous oxides (NOx) and the formation of condensation trails (contrails) from water vapour at near stratospheric levels where commercial jets fly mean the actual impact on global warming is much higher � possibly as much as ten percent. Air travel is also on the rise, with GHG emissions from international air travel jumping by almost 70% between 1990 and 2002. In China, air travel is growing by around 12% per year, and worldwide passenger air travel is increasing by 5% annually, a faster rate of growth than any other travel mode. Air freight has also been growing rapidly, though it remains a small share of total air traffic.