Forget "green growth". Judging by the hard numbers, only two economic factors produce reliably good environmental outcomes: high energy prices and recession. During the era of soaring oil prices, which peaked at just over $140 a barrel in June 2008, people began to do all the things greens have been badgering them about for years: driving less and cutting back on flights, for example.
More recently, the recession has pushed down Japan's fossil fuel emissions by nearly 7 per cent in a year, and the International Energy Agency forecasts that emissions will drop globally by 2.6 per cent. If politicians could claim credit for this unexpected climatic boon, it would be Nobel prizes all round.
Unfortunately, these two drivers of emissions reductions are also the two things that everyone seems desperate to avoid - and there are now reliable signs that the recession in most industrialised countries is ending. But the good news is that oil prices are climbing again: crude is now pushing back towards $80 a barrel, and fears of an oil supply crunch are resurfacing after a rather quiet year for the "peak oil" crowd.
Global Witness, a campaigning NGO, is the latest to issue stern warnings about imminent oil shortages. Its Heads in the Sand report points out that, over the past three years, "conventional oil production ceased to grow, despite massive investment, increasing demand and prices". Moreover, it warns, "the recession does not change the underlying fundamentals" of a widening gap between supply and demand. Instead, it foresees "disaster" if governments "remain committed to keeping their heads in the sand" about the prospect of peak oil.
So why are rising prices presented as such bad news? Oil prices above $100 - or, better still, $200 - a barrel could act as a global insurance policy against the collapse of the upcoming climate change talks in Copenhagen. As fossil fuels begin to price themselves out of the market, they could make up for the failure of politicians to price carbon appropriately to the damage it causes.
The current price of carbon on the EU emissions trading market is a risible 15 euros a tonne, much too low to send a serious signal to Europe's big fossil fuel users. On the other hand, a return to soaring oil prices makes renewables, energy efficiency, nuclear power and other environmentally preferable options much more attractive in conventional economic terms. For these reasons, many environmentalists will mutter privately, if provoked: "Peak oil? Bring it on."
There are, however, dangers of being too simplistic. Oil, for instance, is not the only fossil fuel. The biggest historical contributor to carbon dioxide emissions has been coal, and production of this dirtiest of all fuels has been rising for most of the past decade - led by the surging use of electricity in China. High prices also spur investment in new technologies aimed at converting coal to liquid form (for use as transportation fuel) and in unconventional oil production, both of which have enormous carbon footprints.
Peak oil can help humanity only if we have the wit to use it as a cold turkey opportunity to kick our oil addiction. If we simply increase our efforts to get more of the carbon drug - take the extraction of tar sands in Alberta, Canada, for instance, surely the world's most environmentally destructive industrial project - then the future looks bleak.