The responsible UN body, the International Civil Aviation Organisation (ICAO), based in Montreal, has been discussing the issue for 16 years now. But it took the EU's inclusion of international aviation in its Emissions Trading System (ETS) to really focus minds.
Aviation was included in the ETS on the basis of EU sovereignty - if you fly into Europe's airports, you comply with Europe's laws. The EU required airlines to surrender pollution permits for the carbon emitted during the entire length of all flights to and from an EU airport. Europe did so in the belief that it had the responsibility to reduce emissions from aviation, just as from any other sector of the economy. But other countries cried foul, especially the USA - the world's biggest aviation emitter, accusing the EU of breaching its sovereignty by regulating emissions outside of Europe's borders.
Let's be clear: international law allows countries to set rules for aircraft landing at their airports. The US uses this provision to full advantage by requiring full passenger information before you even board a US-bound aircraft, nevermind before you enter US airspace. And the EU Court of Justice declared the EU's plan legal when it dismissed a challenge from US airlines. No country has ever brought an appeal to the ICAO Council to challenge the legality of the EU action, but the cries of sovereignty breaches continue.
This leads us to where we are today. In order to foster a consensus, the EU recently offered to cut back the EU ETS by regulating emissions only within EU airspace. This is a reduction of over 60% of the intercontinental emissions covered by the original law. In exchange, the EU hopes the ICAO countries will finally agree in Montreal to develop details of a global market-based measure over the next three years, then sign off on the global measure in 2016 and begin implementation in 2020. But divisions amongst ICAO members run deep and it is not clear that this can even be agreed, never mind actually achieved in 2016.
And in any case, even if every country implemented an airspace regime, 78% of global emissions would still be uncovered, with flights over international waters and third countries uncovered. It's hard to see this approach as robust guidance on how to tackle an industry whose climate impact accounts for 5% of global warming.
The aviation ETS became EU law in 2008, and it seems extraordinary that EU member states, with the backing of the European Commission, can now see fit to concede on such a grand scale when the clear divisions in ICAO could well undo any delicate conclusion reached at this Assembly. The fact that the European Parliament has been side-lined in this whole process, not to mention relevant stakeholders like you and I, only makes the story more incredible.
A far more sensible and politically viable solution would have been to revise the ETS on the basis of what we call 50/50. To explain this, let's take a London to New York flight. Under 50/50 the EU would regulate the first 50% of emissions of flights departing London and the last 50% of all flights returning from New York. The US would then have the option to enact a regulation for its 50% of each journey if they wanted to (they won't). Importantly, this solution keeps the environmental integrity of the system. Emissions over the US continent are not taken into account (solving the supposed violation of US sovereignty) and the EU continues to exercise its sovereignty over flights landing at its airports.
It is clear that the EU's concession will fatally weaken EU action on aviation emissions. We can only hope now that as a result of this concession, the US and other countries show sufficient political determination to broker the best possible global deal. After 16 years of delay and the EU's massive retreat, international aviation must now take responsibility for its ever-growing climate impact.