Geoffrey Lean: The end of the Oil Age is in sight, but who is looking?

That was, of course, in the immediate wake of Hurricane Katrina which knocked out a tenth of US refining capacity, sending prices in garage forecourts soaring. Some of the refineries are coming back on steam and pump prices are beginning to ease. But this is likely to be only short-lived relief.

The world's thirst for oil grows ever greater, particularly in the United States and China. In the US - where, until recently, oil cost less than bottled water - demand is booming as the Bush administration scorns any suggestion that the nation should save fuel for environmental reasons. China has just overtaken Japan as the world's second largest oil consumer, and its economic expansion is only just beginning.

This was sending prices soaring before the hurricane struck. But it is nothing compared to what will happen if, as Simmons predicts, the rapid 145-year-old growth of oil soon turns into a decline.

There is, of course, only so much oil in the world, so one day we will reach a peak by pumping out more than we have ever done before, or will ever be able to do again. On that day - dubbed "peak oil" - ever-expanding, generally cheap, supplies of the stuff will turn into shrinking, increasingly costly, ones. If it comes before we are properly prepared, the world economy will slump and conflict increase as nations fight over what is left.

The orthodox oil industry view is that there is plenty of time: peak oil will not occur until the 2030s. But Simmons and a growing number of analysts believe it may be only a couple of years away.

The world has been burning more oil than it has found every year for the past quarter of a century. And, despite vast investment in prospecting, the discovery of new fields is at a record low.

US production peaked in 1971, our own in 1999. The British-based Association for the Study of Peak Oil estimates that the Middle East's peak is just five years away; Simmons believes it may already have passed.

Even if he and his colleagues are wrong, prices are likely to go on rising. There is a shortage of refineries (which is why Sir Richard Branson announced yesterday that he was going to build one of his own), oil rigs and tankers. Worse, a terrorist attack on a major oil refinery, or a radical takeover in a key state such as Saudi Arabia, would cause a major crisis, disrupting the world economy.

As we report today, Bill Clinton believes that rising oil prices are a good thing. That is true, up to a point. Higher prices will encourage the exploitation of less accessible oil reserves.

More importantly, they will boost energy saving and the expansion of renewable energy - also urgently needed to avert global warming.

But all that takes time to bring on stream and, if the pessimists are right, we do not have much of it.

Even if the official view is correct, we need an immediate crash programme on conserving energy and developing renewables if a disastrous shock is to be avoided. For the end of the Oil Age is indeed in sight.