The UK may have to cut emissions² of greenhouse gases by 90% by 2050 so the aviation sector³ can continue to grow.

英国需要在2050年以前将温室气体的排放缩减90%以促进航空业的继续发展。

The rest of the economy may have to make space for aviation emissions

That is the warning from the government's official climate advisers⁴, the Climate Change Committee (CCC).

It would mean even bigger cuts than the 80% drop on 1990 levels already planned for households and industry in Britain.

But the committee also says global aviation（航空） emissions should be capped during the forthcoming Copenhagen climate talks.

The committee was asked by government to advise on what should be done about emissions from aviation.

In a letter to the Transport Secretary Lord Adonis and the Climate Secretary Ed Miliband, the committee says the aviation industry will have to cut emissions from planes back to their 2005 level by 2050.

That is much more permissive（许可的，获准的） than the overall UK target of cutting emissions 80% on 1990 levels by 2050.

The failure of aviation to play its full part could mean that the rest of the economy has to reduce its emissions by 90% instead of 80%.

This 90% target is so ambitious that it might be easier for some sectors⁵ to make the leap to zero carbon emissions rather than trying to whittle⁶ down（削减） pollution decade by decade.

And some analysts⁷ think this might be an easier and cheaper approach than reaching a 90% cut in stages.

The options

The committee members see alternatives.

Planes, they say, might use biofuels or aviation might cut emissions below 2005 levels through new technology.

Plane operators might also be able to buy emissions permits in international emissions trading.

But all of these options carry difficulties of their own. Biofuels compete with crops for land and are already in demand for fuelling cars.

And it looks to be a huge task for aviation to restrict emissions to 2005 levels, even without trying to go further.

And the emissions trading system in which rich countries pay poor ones to clean up their pollution may prove to be a stop-gap solution which could be defunct⁸（死的，无效） by 2050.

The CCC's recommendations are designed to reduce aviation emissions in line with a global reduction in emissions of all greenhouse gases of 50% by 2050.

It says that, if left unchecked, global aviation could account for 15-20% of all the manmade CO2 produced in 2050.

The committee advises that:
All CO2 emissions from aviation should be capped, either through a global aviation deal or by including international aviation emissions in national emission¹ reduction targets;
Any international agreement to reduce emissions should be no less than the EU's target of a 5% reduction in net emissions from 2013-2020;
Emissions allowances for aviation in the EU emissions trading scheme, says the CCC, should be fully⁹ auctioned¹⁰ to prevent windfall profits for airlines;
Funds should be found for radical¹¹ innovation in engine, airframe（机身） and fuel technology;
Additional non-CO2 gases from aviation are contributing to global warming. The effects of these should be addressed within a global deal on aviation.

The CCC's Chief Executive David Kennedy said: "It is vital that an agreement capping global aviation emissions is part of a Copenhagen deal.

"We are calling for a cap that would not require people to fly less than today, but would constrain¹²（强迫，勉强） aviation emissions growth going forward."

The right-leaning think-tank Policy Exchange recently proposed that world production of sustainable biofuels should be diverted from cars to planes in order to overcome the lack of current breakthrough technologies in aviation.