Caroline Lucas: The Green case against airports

You could be forgiven for thinking a third runway at Heathrow dead in the water, since all three main parties were against it. But this week the debate was revived with some macho posturing from Tim Yeo, the chair of the Committee on Energy and Climate Change, who urged David Cameron to prove his "strength" by changing his position. So far, this has been given short shrift by the Transport Secretary, Deputy Prime Minister and No 10. However, as Tory frustration mounts over the economy, we can be sure the debate – and the aviation lobby's insatiable appetite for growth – will rage on.

Some perspective is crucial. The reality is that endless growth in our aviation capacity is not sustainable. Aviation is one of the fastest-growing sources of greenhouse gas emissions, and already contributes to 13 per cent of our GHGs once non-C02 emissions – including soot, nitrogen oxides and water vapour – are taken into account. Worryingly, the non-C02 effects – nearly double that of C02 alone – are not included in the Climate Change Act nor in the advice to Government from the Climate Change Committee (CCC). Neither are they factored into the EU's Emissions Trading Scheme. The failure to take non-C02 emissions into account means that this is not the get-out-of-jail-free card for the industry Yeo and others would have you believe.

Essentially, unchecked growth in capacity at Heathrow and elsewhere would make it impossible for the UK to meet its emissions reduction target of 80 per cent by 2050 – one which already falls short of what the science requires.

The pro-expansion lobby makes bold claims about growing demand. But the Government's forecasts indicate that even if airport growth could continue free of environmental legislation, passenger demand could be met solely via the existing infrastructure until almost 2030. They also overestimate demand by assuming economic growth of two per cent or more a year (a fantasy), a continuation of aviation's outrageous tax exemptions, and no increase in oil prices.

The Government must ignore the weak arguments for never-ending airport expansion, and instead reduce demand. Only by dropping the third runway obsession and recognising the ecological constraints on aviation expansion can we hope to have cleaner air to breathe, less noise pollution for those under flight paths – and to take a lead in the fight against climate change.