Britain faces the prospect of closed filling stations and empty supermarket shelves as the fuel protesters once again threaten blockades. Last time the problem went away within a week or two. The hope is that this time too, the crisis will quickly evaporate. But there are scientists who believe that the recent problems are just a foretaste of what is to come - all the time and very soon. They predict that from 2005, the world will face a permanent and deepening shortage of petrol and diesel. 

Geologist Dr. Colin Campbell warned, "The recent disturbances in Britain are like the tremors that precede an earthquake. The earthquake, which is almost now upon us, marks the beginning of the end of the age of oil." He and a growing band of supporters believe that, in the crisis we now face, we have glimpsed the future. And the future is about to arrive. 

The world is utterly dependent on oil. The first modern oilfields were discovered in Pennsylvania, in the United States, in 1861 and global prosperity grew as the torrents of oil flowed. We depend on oil for petrol and diesel and therefore for transport. On land, sea and air. We depend on oil for the transportation of goods and food. We depend on oil for plastics. We depend on oil for agricultural fertiliser. Everyone is agreed that oil is running out. In 1998, the world consumed more than three times the amount discovered, according to IHS Energy Group, the leading oil and gas information firm.. When the oil does run out, without an alternative, the consequences will be severe. The question is when and how. The school of thought predicting early depletion is led by Dr. Campbell. In a 45-year career as an exploration geologist, working for BP, Texaco, Amoco and Fina, he has looked for oil all over the world. 

After studying data from the world's 18 thousand oil fields, Campbell concluded that the oil will begin to run short in five years time. He said: "From 2005 onwards, we see the beginning of the long term decline in conventional oil production. I think it will probably fall roughly 3% a year. "Demand, on the other hand is growing at 2% a year. That means there's a shortfall, and by about 2020, there will be a shortfall of something like 40%." Scarcity will drive up the price. Economist Andrew Oswald of Warwick University explained what that means: "Some kind of economic slow down is inevitable. We've seen more than a trebling in the oil price in the last year and a half. "If the price went up to say 50 dollars a barrel then it would become very serious indeed for western economies. "Currently we don't know how bad an economic slow down would be produced, but certainly if the price keeps going then in the long run we're in trouble." 

Speaking in a personal capacity, Richard Hardman, vice president for exploration for American oil producers Amerada Hess, went further: "I think there will be a real crunch. There will be a competition for this scarce resource - the oil. It means that there could be famines and wars." Campbell and Hardman acknowledged that doom mongers have falsely predicted oil dearth before. And they have been proved wrong by new discoveries. But, they said, high tech "global X-rays" now enable the industry to determine far more accurately how much oil is left to discover -- and it's not much. Said Hardman: "People have cried wolf in the past many times. I believe that this time the wolf really is at the door. "And I believe that, because, for the first time, we have a systematic survey of all the major sedimentary basins in the world. And we've got a calculation of what reserves they can contain." 

Campbell and Hardman have updated a theory first expounded by Shell geologist King Hubbert in the 50s. He said that the big oil fields are discovered first, they are easier to exploit and the oil runs freely and cheaply. When they've gone, the industry turns to the smaller, more difficult fields. There will always be oil in the ground. But as the oil depletes, it eventually becomes impossible to pump. Oil discovery in the United States peaked in the 50s and then declined. Hubbert argued that production rises, peaks and falls in the same way after a time lag. He predicted that US production would peak in 1970 and then decline inexorably. It has. Campbell calculated a "Hubbert curve" for the world which sees production peaking in 2005 and thereafter declining. The decline will start first outside the middle east. The world will then become increasingly dependent on countries such as Iraq, Iran, Kuwait and Saudi Arabia, said Campbell. But their production will start to decline not long after. And then the need for an alternative will become ever more pressing. 

Campbell dismissed gas as a viable alternative long term on the grounds that gas field discovery and production follow the same pattern as oil -- and gas supplies will decline not long after oil. The Germans, with hardly any oil of their own, take the issue more seriously than in Britain. They have formed a coalition of oil companies, car companies and Government to seek long term alternatives. As part of that project, BMW has spent vast sums developing vehicles run on hydrogen. They emit only water vapour. BMW chief of science Detlef Frank said: "We can face the future only if we have unlimited access to fuel for mobility -- and the only alternative we know of is hydrogen." But there are only two hydrogen filling stations in Europe -- at Munich Airport and in Hanover. A vast new infrastructure to supply hydrogen would have to be built. 

BMW has a vision of a future powered by non-pollutant hydrogen fuel produced from water by electricity created through solar power in a totally clean and renewable cycle of production. Dr. Roger Bentley of Reading University, applauds BMW's efforts but concluded: "There's nothing wrong with the idea of a hydrogen economy. But none of it can happen in the timescale to help solve the oil crisis. "Hydrogen needs energy to produce it. Solar panels may be one of those sources, but its all very expensive at the moment. There's a lot more development to be done. And as yet the infrastructure is not in place." So what hope for the world? Are the doomsayers wrong? 

Putting the optimistic case is Ged Davis, Shell International's vice president global business environment. He believes we've got 20 years before oil depletion becomes "an issue." At the moment only 35 per cent of oil reserves are recoverable. Ged Davies believes better technology will enable the industry to extract a greater proportion of existing known reserves. He also believes that the industry will discover more oil fields. He said: "I think you can make a very clear case that if one looks for example over the next twenty years, that most of the additional oil that will be needed in the marketplace will be met either from exploration and equally from improved recovery." American oilmen, however, believe that, with oil as with much else, what happens there first then happens all over the world. And the annual rate of oil production in America has been in decline since 1970, falling by a third. 

Texan oil producer Jim Henry said: "I've seen it decline. Elsewhere they've seen production increase and they don't realise that some time it peaks. And when it peaks then it starts declining. "Production goes down because the large fields are declining, the smaller fields are on stream but they don't produce nearly as much as a larger field. And overall the production declines. "High technology in my opinion can never stop the decline. It might at some time arrest it for a year or two, but the decline is inevitable." 

Dr. Colin Campbell might be expected to condemn the fuel protestors for demanding cheaper prices and thus hastening the depletion of reserves. Instead he said: "The fuel protesters have done us a service by letting us know just how utterly dependent on cheap, abundant oil we have become." However he looks forward to the day when protestors take to the streets to demand - not cheaper oil - but renewable alternatives to oil.