MONTREAL (AFP) - The airline industry's mouthpiece called on Monday for uniform global measures by 2020 to curb all aircrafts' carbon emissions, warning that a patchwork of competing proposals could emerge otherwise.

And if that happens, it could lead to a proliferation of trade wars, said International Air Transport Association general manager Tony Tyler said at a meeting of the international industry trade group of airlines.

Tyler said he remains "optimistic" that IATA member states will come together on a plan.

"We think that a global mandatory carbon offsetting scheme would the simplest, easiest in the end to implement," he said.

"We have seven years to do it," he added. "It's achievable." But if IATA member nations fail to reach a consensus on what a global airline carbon tax might look like, he warned, "We could well see a proliferation of regional schemes of taxes, charges, different ways of penalizing the industry.

"This could lead to overlapping, duplicating, sometimes conflicting schemes under which we may be paying twice for the same emission." Several nations have already balked at a global emissions scheme for airlines, including the United States and India.

Late last year, after running into a storm of criticism, the European Union suspended its CO2 Emissions Trading Scheme (ETS) for intercontinental flights for 2013, saying it wanted to give all sides more time to reach a global accord.

Under the ETS, airlines flying in EU airspace were required to buy pollution credits to cover 15 per cent of their CO2 emissions for the entire flight, wherever it originated.

A European source said earlier this month that the EU is ready to compromise over its tax if opponents, led by the United States and China, apply a similar levy by 2016.