Britain finally confronted the point of a decision on a difficult question that it had ducked for far too long. Or, at least, that is how the Airports Commission presented its endorsement of an extra runway at Heathrow. The airwaves reverberated with the voices of the sort of men who never shrug off a boyhood Airfix fixation, arguing with burning intensity about whether the precise spec and coordinates of the Heathrow proposal, and its Gatwick rival, had the makings of a world-beating hub. A few voices were raised about the “environmental” effect, in the sense of the immediate local environment – questions of noise, of birdlife and the extra fumes that could soon be inhaled by the suffering lungs of Middlesex. These are all real issues, but together with the diversionary debate about “where” rather than “whether”, they pale besides aviation’s contribution to the planet’s slow cooking. If there is a difficult question that has been ducked for too long, then that is the one about decarbonising the economy.

To be fair to Sir Howard Davies, his commission did not ignore carbon. The report predicated its projections of passenger growth on two scenarios, both of which it said could respect UK carbon obligations. The first involved a rigid cap on aviation emissions, a little above current levels. The commission stuck a finger in the air and ventured that this might be compatible with a 61% rise in passengers by 2050, a calculation that must rely on engineering advances easing the brute, energy-intensive physics of lifting people and machinery into the air. The emphasis, however, and the basis for arguing that increased capacity was not merely desirable but imperative, was on a second, fairytale future, in which passengers double, under the auspices of comprehensive and globally enforced carbon trading.

At a time when European integration is under strain, the invitation here is to imagine that something akin to the EU emissions trading system is first extended to the rest of the world, and then made so much more effective that the carbon price rises from a few euros a tonne to something in the hundreds. If all this can be put into practice, then, the theory runs, the value of UK flights will be such that the aviation sector will be able to outbid British factories and foreign enterprises in the scramble for carbon rations. That is a dubious proposition. For all the talk of Heathrow as an engine of growth, many of the new jobs would be low-tech and low-pay: serving the coffee in another Costa, or lugging more suitcases out of holds. The official figures confirm that the proportion of flights dedicated to business is lower than it was at the dawn of the millennium, the result not only of passing recession, but also the march of things like Skype, which allow more business meetings to be held online.

Seeing as – in all likelihood – the price of carbon is not going to rise to the point where the climate problem is fixed, the pertinent question is whether the actual price of flying is going to get closer or further away from where the planet would want it to be. Building more capacity is going to reduce the cost of taking an extra flight: that is its principal aim. It will mean more people choosing to fly, rather than holidaying closer to home, or taking the train. Indeed, nothing betrays the mindset more than the way in which the commission held up the downward trend in regular domestic flights into Heathrow as if this were a problem. It is part of the solution.

In 2009, David Cameron stood against expanding Heathrow, linking his opposition to support for high-speed rail. That grand project may be on track, but other important rail upgrades have just been postponed. The Guardian’s Keep it in the Ground campaign has pointed out that existing fossil-fuel stocks are more than sufficient to unleash climate chaos; the same thing is true of the existing infrastructure. Transport networks need to be re-engineered for decarbonisation. But that would require some real blue-sky thinking, and of that there is no sign.