Peak oil adherents with an even darker view say the world is on the cusp of a global recession, widespread famine and constant warfare between nations desperate to secure what's left. Human extinction is a possibility, the most pessimistic believers say.
Not everyone who has studied the world oil supply believes production is about to peak. Researchers at the U.S. Energy Information Administration say they believe production will not peak until 2037, while other analysts point out that previous predictions of a peak date proved to be wrong.
Those who believe that depletion is imminent are sometimes derided as Chicken Little-like eccentrics, as they tell governments, the media, the energy industry and just about anyone else willing to listen that the world is on the front edge of an emergency.
One of the worriers is David Goodstein, a physics professor at the California Institute of Technology. In his book, "Out of Gas: The End of the Age of Oil," Goodstein writes that once production peaks, people will have to switch to alternative fuels in time to meet rising energy demand. Otherwise, "runaway inflation and worldwide depression" will force billions of people to burn coal, he says.
The so-called "greenhouse effect" — the rise in temperature caused by gases trapping energy from the sun — could make the planet unlivable, Goodstein says.
"End of story," is Goodstein's somber conclusion. "In this instance, worst case really means worst case."
Goodstein acknowledges that though it's impossible to predict all the effects, "We can all too easily envision a dying civilization, the landscape littered with the rusting hulks of useless SUVs."
But doomsday is avoidable, says Goodstein, who believes that the peak may hit this decade. Methane could fuel the world economy temporarily until more nuclear plants are built and the infrastructure for producing and using other energy sources is in place, he says.
Goodstein writes that if the human race gets over the shock of no more cheap oil and switches to coal and natural gas, life could continue without big disruptions. But by the end of the 21st century, the world will begin to run out of all fossil fuels under this scenario, he says.
"We may well have rendered the planet unfit for human life," he says. "Even if human life does go on, civilization as we know it will not survive, unless we can find a way to live without fossil fuels."
In an interview, Goodstein indicated that he tries to do his part. He drives a hybrid car, which runs on a combination of gasoline and electricity, and lives close enough to his job that he can walk some days. But he realizes his contribution is small.
"What I do doesn't make very much difference," he says. "I don't use 20 million barrels of oil a day."
Richard Heinberg, a professor of human ecology at New College of California and author of a book called "The Party's Over: Oil, War, and the Fate of Industrial Societies," also has no illusions about his ability to make a difference.
But Heinberg, who expects peak production in 2007 or 2008 and $5-a-gallon gasoline by the end of the decade, shows his conviction with his lifestyle. He tools around in a 1980 Mercedes that runs on modified vegetable oil — or "biodiesel" — and lives in a house that gets its electricity from the solar panels he installed for $10,000 three years ago.
Heinberg, who also wrote a book called "Powerdown: Options and Actions for a Post-Carbon World," is a member of a co-op at his school that buys the biodiesel in bulk.
Nobody disagrees that production eventually will peak, because the amount of oil in the Earth is finite. It also is clear that population increases and rapid economic growth, particularly in the United States, the world's wealthiest nation, and China, the world's most-populus nation, will continue to drive up demand.
The father of the theory is Marion King Hubbert, a Shell Oil Co. geologist who predicted in 1956 that American oil production would peak between 1966 and 1971. Skeptics questioned Hubbert's projection, but U.S. crude oil production reached 9.64 million barrels a day in 1970 and by last year had dropped to 5.74 million barrels, according to the EIA.
The world produced 69.3 million barrels of crude oil a day last year, the largest total on record. The United States was the largest consumer of petroleum, using 20.04 million barrels a day.
The potential effects of a serious shortage go far beyond stress at the gas pumps. Nearly everything we eat or use was made or transported with a fuel made from petroleum. The fuels power factories, farm equipment and ships. They heat homes and businesses. Fertilizers and insecticides are made from oil.
Oil is used to make most organic chemicals — or petrochemicals — including pharmaceuticals, agricultural products, plastics and fabrics.
High oil prices drive up the prices of goods and services and eat up the money people would rather spend on food, clothes, vacations, houses and other pleasures and necessities. That hurts those businesses and their employees. Every recession since the early 1970s was preceded by a sharp rise in oil prices.
Some researchers who have studied oil supplies believe that the peak in world production is decades, not years, in the future. They point to numerous variables, such as the development of alternative sources of energy, the possibility of finding new fields and the emergence of technologies that could make it economical for producers to pull more oil out of a field than they do now.
They also point to the possibility of new conservation strategies, such as hybrid cars like the Honda Civic Hybrid and the Toyota Prius.
Myriad geopolitical, economic and other factors — such as a large terror strike on oil infrastructure — could affect the supply, making predictions dicey, some say.
Higher oil prices also could trigger energy-saving cultural shifts leading to more use of public transportation, a migration from the suburbs into cities as people look to shorten their drive to work or a boomlet in sales of small cars like what occurred after the Arab oil embargo of 1973.
Any one of these trends would delay the peak.
A.F. Alhajji, an associate professor of economics in the College of Business Administration at Ohio Northern University in Ada, Ohio, says the first predictions that the world was about to run out of oil surfaced in the 1890s, less than 40 years after the first oil well was drilled in northwestern Pennsylvania.
"A hundred of years of wrong predictions," says Alhajji, who believes predicting a precise peak date is nearly impossible. "What kind of science is that?"
The peak theory does not appear to have gotten through to those in the boardrooms of some of the world's largest oil companies. Research into renewable sources of energy such as the sun, wind and water might yield results years from now, but shareholders aren't usually a patient lot.
Lord Browne, group chief executive at BP PLC, reported in a June speech in Washington, D.C., that his company is researching photovoltaics — the technology that produces electricity directly from sunlight. But he says it may be at least 20 years before the world can rely on so-called renewable sources of energy, such as the sun, wind and water for significant amounts of energy.
That means relying on oil, gas and coal, he says.
"Can the oil and gas industry meet that demand?" he says. "In physical terms, the answer is clearly yes. The physical resources are there."
Exxon Mobil Corp. says in a February report that it is eschewing research into renewable sources such as wind and solar because they are not sound short-term investments. The company is researching technologies that would make it easier to find reservoirs of fuel, hydrogen production for use in fuel cells to power cars and more-efficient engines.
Though officials in the federal government believe production will hit a peak, they are more optimistic about the timing than some other experts.
At the U.S. Energy Information Administration, three analysts examined about a dozen different possible scenarios in concluding that production is most likely to peak in 2037.
David Morehouse, an EIA geologist and one of the authors, says the estimate is based on the premise that the Earth contains 3 trillion barrels of recoverable oil, the amount estimated by the U.S. Geological Survey.
"Many modelers who say it's sooner have convinced themselves that the resources base is smaller than many of us think," he says.
The geological service estimates are "the most complete and thorough estimate for world oil," ever compiled, he says.
The authors' estimate also assumes crude oil production will increase about 2 percent a year, Morehouse says.
He says their conclusion covers only oil in conventional oil reservoirs. It does not include so-called "heavy oil" or tar sands that are plentiful in parts of Canada and Venezuela. Tar sands can be processed into petroleum products and, if exploited, could add a couple of decades to the peak date, Morehouse says.
But he acknowledges that tar sands are difficult to get out of the ground. The tar sands in Venezuela flow slowly, while those in Canada require steam injection to flow, he says.
Despite taking a rosier view than some, Morehouse and his fellow authors urge the world to pay attention to the phenomenon.
"This result in no way justifies complacency about both supply-side and demand-side research and development," they conclude.
President Bush and his Democratic opponent, Sen. John F. Kerry, both preach the need for the United States to be less dependent on foreign oil, but they differ on strategy.
Bush boasts of having increased research into making electricity more reliable and of filling the Strategic Petroleum Reserves to their capacity of 700 million barrels that can be tapped in an emergency. The president wants to drill in the Arctic National Wildlife Refuge, burn more coal and speed up the permitting of exploration on federal and tribal lands.
Kerry emphasizes research into new energy sources and pushes $10 billion in incentives to encourage automakers to make fuel-efficient cars. He also advocates a $4,000 tax credit for people who buy those gas-stingy cars.
Those who believe the peak is coming soon see a rising threat to the existence of the human race.
Matthew Simmons, who runs a Houston-based investment bank specializing in energy, says he believes that the world needs to curtail its oil production for several years while trying to get a better handle on what's left of the supply.
"It's very complicated, but the idea that it's not around the corner is really far-fetched in my opinion and it (peak production) may have already passed," says Simmons, who is writing a book about the depletion of Saudi Arabia's oil reservoirs.
Simmons says many of the world's largest oil fields, particularly those outside the former Soviet Union and the 11 nations that make up the Organization of the Petroleum Exporting Countries, no longer produce the volume they once did.
Though the yield from Russia and other parts of the former Soviet Union has increased in recent years, that growth has come because producers have squeezed old fields, not because they've discovered new fields, he says.
"It's really hard to find an area outside of OPEC that you could make you put your hand on your heart and say, 'I see a lot of growth coming in the next five years,' " he says. "Maybe we'll find a new basin somewhere, but we haven't done it in 30 years."
Simmons looks around the world and sees no other reasons for encouragement.
He says China has two fields, Daqing and Shengli, that account for 50 percent of that country's production. He says internal reports estimate production in these fields will drop by half in the next five years.
The bulk of Mexico's production comes from Cantarell Field, where it took a $10.5 billion nitrogen injection project to increase production.
The North Sea — between Great Britain and the European mainland — and Iran are other areas in decline, he says. Iraq's fields are being surveyed, but the nation's oil infrastructure was badly damaged by Saddam Hussein's neglect and war.
"There is a lot of potential for negative supply surprises," Simmons says. "There is very little potential for positive supply surprises."
It's a problem the world has been slow to recognize, and time is running out, he says.
"How do you solve it?" he says. "I don't know, but if you don't solve it, it's a show stopper. If you come back and think about the role of what modern energy plays in society, it's water, it's food, it's transportation. You really get into talking about much more than just motor gasoline prices."