Dominic Lawson: Fight climate change? Or stay competitive? I'm afraid these two aims are incompatible

Isn't politics wonderful? Within days of Gordon Brown's address to the conservation group WWF, in which he pledged eye-wateringly tough reductions in British emissions of Co2, the Government has announced its support for the construction of a third runway at Heathrow Airport. "This time he really gets it," Greenpeace's executive director had enthused after the Prime Minister's "Let's save the polar bear" speech. Yesterday, following the Transport Secretary's endorsement of BAA's expansion plans, Greenpeace was back to its default position, spitting ecological tacks.

You might think this is a case of the left hand not knowing what the right hand is doing (or possibly the left hand not knowing what the left hand is doing) especially given the Government's growing reputation for administrative chaos. In fact it is entirely deliberate. The Government both wants to claim "leadership in the fight against climate change" while at the same time it – quite understandably– does not want to do anything which might reduce this country's international competitiveness. It knows that these two objectives are incompatible – very well, then: it will contradict itself.

Gordon Brown's commitment to the most stringent reductions in C02 emissions yet announced by a British Prime Minister follows exactly the path set by his predecessor. Mr Blair would, with a great moral fanfare, pledge this nation to achieve some carbon emission target. Then, when it became completely clear that we were not on track to meet it, he would announce – with equal confidence and certainty – not an easier target but an even tougher one than that which we were failing to achieve.

The civil servants who live in the real world of facts and actually have to devise the practical policies to meet these political flourishes have become increasingly panicky. A month ago there was a leak of an especially desperate memo in which officials warned that the previous Prime Minister's commitment to produce 20 per cent of our energy from renewable sources by 2020 was facing "severe practical difficulties".

As we know, that is senior civil servant speak for "this will be absolutely impossible." One of the memos rather plaintively pointed out that if we admitted this publicly and tried to advocate a general lowering of such targets internationally, there would be "a potentially significant cost in terms of reduced climate change leadership".

Here we see the absurd grandiosity of our global ambitions, partly a legacy of Tony Blair's messianic approach, but which is to some extent a characteristic of the British political class as a whole. More than half a century since the collapse of the British Empire, our leaders still seem to think that what we do or say is as important in the eyes of the rest of the world as it was when we really did rule the waves. It is a grotesque vanity, economically as well as politically.

It has been written often enough that any likely reduction in Co2 emissions from our own generation of electricity is not just sub-microscopic in terms of any measurable effect on the climate: the People's Republic of China is now opening two new coal-fired power stations every week. Real "climate change leadership" would be developing "clean coal" technology and selling it to the Chinese – but for some reason that does not fascinate politicians in the way that targets do. It is insufficiently heroic.

We can see the same national self-obsession in the debate over the environmental consequences of opening a third runway at Heathrow: last year China announced plans to expand 73 of its airports and build 42 new ones. Yes, the British government could demonstrate "increased climate change leadership" by blocking BAA's plans to build another runway at Heathrow. Does anyone seriously imagine that the consequence of further congestion and delays will be something other than a transfer of traffic from that airport to others in the immediate vicinity, such as Charles de Gaulle, which already has much more capacity?

For those on the provisional wing of the British environmental movement, arguments about a loss of business to other countries are irrelevant. They would insist that this complaint makes no more sense than saying that it's necessary to sell arms to unpleasant dictatorships because if we don't, other countries will, to the benefit of their own economies.

If, like George Monbiot, you regard flying as morally equivalent to "child abuse", then, yes, the executives of BAA should be thrown in jail ( after a fair show trial, of course) and never be let out. As for any recession deriving from a closing down of Heathrow – pah! A recession would be a good thing, since it would lead to further reductions in Co2 emissions.

I accept that there will be many sensible people living in the area around the Heathrow Terminals who will not welcome the increase in planes taking off and landing. On the other hand, there has been an aerodrome at Heathrow since the 1930s and the first Terminal was opened by the Queen in 1955: that is to say, there are unlikely to be many home-owners living in the Heathrow area who bought under the impression that he or she would enjoy peace and quiet. Doubtless the property prices there reflect that fact.

Anyway, why worry about airports when we are going to ban the plastic bag? That, you will recall, was the "eye-catching initiative" within Mr Brown's WWF speech. It was artfully designed to capture the headlines in the popular press, and duly did so. The Prime Minister declared that we should "eliminate single-use plastic bags altogether in favour of more sustainable alternatives." Perhaps, since Mr Brown argued that fighting climate change was the political challenge for the younger generation, students should already have been marching on Whitehall with placards declaring "Ban the Bag."

The only problem with that is that plastic bags, though undeniably irritating when left lying around, are essentially the by-product, rather than the cause, of fossil fuel generation. Approximately 98 per cent of every barrel of oil, once refined, is consumed as petrol or diesel. If the remaining two per cent of naphtha was not used for packaging, it would almost certainly be flared off – which is pure waste.

Paper bags have the reputation of being environmentally sounder, but I don't see how this can be justified. They require significantly more space in landfill, being much less compressible – and don't they come from trees, which we are meant to be preserving as capturers of Co2? Besides, if the plastic bag is to be banned, what are we going to use to line our rubbish bins? We need to know the answer to such important questions, Prime Minister, before we allow you to put us forward as the saviours of the planet.

d.lawson@independent.co.uk