It has become clear that any practical idea of how to cut carbon emissions will meet strong public opposition. A YouGov poll for the Sunday Times, in the wake of the climate-change bill, finds higher petrol taxes are opposed by 63 per cent, road pricing by 69 per cent and higher flight taxes by 60 per cent. Similar proportions think politicians use climate change as an excuse for higher taxes. So why do all the main parties think they need to embrace greenery?
The answer, I suppose, is that global warming fears nag at voters' minds and they want reassurance that the government is doing something, thus releasing them from personal guilt. It is politics as therapy, pioneered by new Labour, which promised to reduce poverty and inequality without pain for the affluent. Climate change often seems too big for any individual to make a significant difference but, paradoxically, it offers a wide choice of small guilt-reducing actions - switching off the TV standby, turning the heating down a degree, taking the bus - so that anyone can say they're already doing their bit. Call it gesture politics for the masses.
But there's a genuine problem with green taxes: they are potentially regressive. True, the majority in the lowest income quintile don't have a car and the D and E social classes are eight times less likely to fly than As and Bs. Yet when the poor do drive or fly, however, the costs can account for a high proportion of their income. And for them, travel isn't usually an optional luxury. Think of migrants who want the cheapest flight possible to visit elderly parents in Pakistan or Poland. Or of rural residents who need a car to get to a job.
If we really cared about poverty, we'd raise benefits and the minimum wage. But leave that aside for now. Is there another way of controlling carbon emissions that doesn't increase the cost of essential fuel use but does discourage excess? Carbon rationing seems to do exactly that.
Elegant and just
The idea was first floated by environmentalists in the early 1990s, and it has long been Green Party policy (I mention that to save the editor printing a letter from the Greens next week). But David Miliband, the Environment Secretary, was the first prominent politician to give it an airing. He invited us last year to "imagine a country where carbon becomes a new currency. We carry bank cards that store both pounds and carbon points. When we buy electricity, gas and fuel, we use our carbon points as well as pounds." The government would give everybody the same free points. Those who didn't need them all, including the poor people who don't drive or fly, could sell their surplus to people who wanted to run an SUV or jet to Spain every weekend. Though a Policy Studies Institute report (The Distributional Impact of Economic Instruments to Limit Greenhouse Gas Emissions by Simon Dresner and Paul Ekins) has calculated that some poor people in damp old houses might still lose out, the overall effect would be more progressive than green taxation, particularly if domestic fuel were excluded from the equation.
The scheme looks elegant and just. It recalls wartime rationing of food, clothing and petrol, which commanded general public support and didn't completely end until 1954. But there's a difference. The wartime government considered tradable rations but ruled them out because, as a recent paper from Mark Roodhouse, an historian at York University, puts it (www.historyandpolicy.org/  archive/policy-paper-54.html), they feared they would "undermine the moral basis of rationing: equality of sacrifice". The resulting black market never developed its full potential because, as Lord Woolton, the food minister, said, "the correctness of its purpose and the fairness of its administration" was widely accepted, and the public "trusted the government's judgement".
Morality, equality, sacrifice, fairness, trust: to see those words in a public policy debate is to realise the gulf that separates us from our parents and grandparents. Governments have insisted not only that individuals have a right to judge their own needs and choose their public services accordingly, but also that choice leads to more efficient provision. This large bird is coming home to roost.
Politicians increasingly find themselves holding the ring between competing demands for individual gratification, rather than establishing a notion of the common good. We see it in debates over access to NHS treatment or school admissions. We shall see it again - sometimes in ugly form, as during the fuel-tax protests of 2000 - as the climate-change debate develops. To judge the size of the problem, go to the Downing Street website. A petition against road pricing: 1,810,655 signatures. A petition for carbon rationing: 1,956. Still, the second one isn't yet closed, so NS readers have time to swell the numbers.