Greenhouse gases from airliners' exhausts make up 3 per cent of global warming but by 2050 could account for 15 per cent, according to figures in the study from the UN's Intergovernmental Panel on Climate Change (IPCC).
More fuel-efficient engines will not stop emissions rising, because the number of people flying continues to increase remorselessly, the report says. It suggests taxes and subsidy deprivation may reduce the demand for air transport, and railways should be encouraged as an alternative to short flights.
The report is believed to be the first time that the international scientific community has called for a reduction in the growth in air traffic and presents a serious challenge to the aviation industry.
But significantly, the final version is less direct than the initial draft, reflecting the wishes of the aviation industry figures in the 100- strong team that compiled it.
The problem that air travel poses for the climate, the report says at the outset, is that "aircraft emit gases and particles directly into the upper troposphere and lower strato- sphere where they have an impact on atmospheric com- position." These include much carbon dioxide and water vapour, the two principal gases causing the greenhouse effect, the increased retention in the atmosphere of the sun's heat, as well as other greenhouse gases such as oxides of nitrogen and sulphur.
Air travel has been growing at nearly 9 per cent a year since 1960, the report says (although it has now slowed to an annual growth rate of about 5 per cent) and so emissions continue to rise.
Fuel consumption by civil aviation is expected to reach 300 million tonnes in 2015 and 450 million tonnes in 2050 - compared with 130 million tonnes in 1992 - with corresponding higher emissions.
"Although improvements in aircraft and engine technology and in the efficiency of air traffic systems will bring environmental benefits, these will not fully offset the effects of the increased emissions resulting from the projected growth in aviation," the study says.
Simon McCrae, aviation campaigner at Friends of the Earth, said: "This report proves aeroplanes are a significant threat to the world's climate.
"If current trends continue, greenhouse gas emissions from planes will rise, potentially undermining international treaties to protect the world's climate. Only a cut in the forecast use of planes will reduce overall aviation greenhouse gas emissions."
A spokesman for the British Air Transport Association said: "The IPCC report acknowledges that today's aircraft are 70 per cent more fuel-efficient than they were and that the industry will generate a further 50 per cent improvement in the years to come.
"An airliner is more fuel- efficient than a train or a car. But IPCC also acknowledges that there are considerable uncertainties about whether emissions from aircraft have an environmental impact and further work is needed to determine the real impact of aviation on the environment."Reuse content