| Air travel is a relatively small source (about 3%) of the world’s greenhouse gases blamed for global warming but it is also a rapidly growing one, more than 5% a year. Aviation accounts for 13% of CO2 emissions within transport. But the overall impact of planes on global warming could be two to four times that of their CO2 emissions alone. High altitude emission are more damaging. The nitrogen oxydes from engine exhausts lead to the formation of ozone, another greenhouse gas. Contrails are suspected to add to global warming. Air travel is not very efficient. Long-haul flights of more than 1,500km are 50 % worse than petrol cars for each passenger-kilometre in term of CO2 emissions. Air travel has been excluded from the Kyoto Protocole and airlines pay no taxe on the fuel they use for international flights. |