Here we go again: the spike in global oil prices that preceded the Great Recession is being repeated. Just three years ago, the price of oil futures on the New York Mercantile Exchange hit $100 a barrel for the first time ever, bringing dire warnings about looming economic hardship. Sure enough, the world economy entered its worst downturn since the Depression just months after oil prices peaked at a record $147 a barrel in July 2008. Now the doomsayers are back, as oil futures crept above $92 a barrel this week - their highest level since 2008.

Fatih Birol, chief economist at the Paris-based International Energy Agency, which represents the world's industrialized oil-consuming countries, warned on Monday that oil prices are expected to reach $100 a barrel again soon, threatening the economic recovery by hugely increasing the energy bills of countries, factories, cities and drivers. Birol warns that the rising price "is a wake-up call." View photographs of South Africa's oil-from-coal refinery.

But what exactly should we be waking up to this time? The 2008 price surge was explained by simple supply and demand: not enough oil was being pumped to meet the voracious appetite of Asian economies, particularly China and India, for whose high-speed expansion oil suppliers had failed to plan. Today, however, there is enough spare oil warehoused, and demand remains relatively weak after two years of recession. Even if supplies tighten, some specialists believe that more oil could be brought to the surface fairly quickly. Saudi Arabia, the world's biggest producer and the powerhouse of OPEC, which produces about 40% of the world's oil, is pumping well below its capacity. And the growth in Iraq's output in the next few years, as international oil companies revamp the country's giant fields after years of stagnation, will boost global supplies. "There is space capacity in OPEC," says Olivier Jakob, managing director of PetroMatrix, an energy-analysis firm in Switzerland. "The financial picture is very different from 2008."

The current spike in oil futures, say Birol and Jakob, is a product of excess supply - of speculative dollars, billions of which are flowing into U.S. commodities markets. "The investors are using their cards to their benefit," Birol told TIME on Thursday. "The way they're reading the market, they feel that when the U.S. recovers there will be a strong demand and a tightness" in oil supplies. Commodities investments in general have soared since August, when Federal Reserve Chairman Ben Bernanke announced the quantitative-easing program to boost the supply of investment capital. "Before the Fed announcement, net interest in crude oil was fairly neutral, but it has now climbed to the highest level ever," says Jakob. "The U.S. Fed is injecting about a trillion dollars into the economy in six months, and that liquidity has to go somewhere. Some of it has gone into commodities." View photographs of the 2008 global food crisis.

Oil is not the only crucial commodity whose price is soaring. The U.N. Food and Agriculture Organization (FAO) announced on Tuesday that food prices had hit a record high, after staples such as wheat, sugar and corn rose more than 4% between November and December. That, says the FAO, is partly due to the booming commodities markets. The organization tracks a basket of staples as an indicator of world food prices. FAO's senior economist Abdolreza Abbassian told the Financial Times that the trend was "alarming," and that it would be "foolish to assume this is the peak."

A combination of rising food and energy prices could ignite a repeat of the food riots that spread across the world in 2007 and 2008, provoking violent clashes from Haiti to Cameroon to Bangladesh. Rising oil prices are already causing major problems in some countries. On Thursday, Pakistan's Prime Minister Yousuf Raza Gilani dropped his Jan. 1 plan to raise fuel prices by 9% - an increase needed to bring relief to badly stretched public finances in a country where government subsidies are so large that drivers pay about 28 cents a gallon for gas. The reversal was a desperate attempt to save Gilani's already fragile government from collapse after the announcement of higher fuel sparked major political protests. View photographs of Azerbaijan's oil boom.

The price surge is being felt even in the U.S., where drivers on average now pay about 40 cents more per gallon at the gas pump than they did six months ago. And airfares have risen for the same reason. (Comment on this story.)

Several other governments that have long relied on fuel subsidies to garner public support now face tough choices. Iran has steadily raised gas prices in recent months, and Bolivia hiked its fuel prices by 80% last month. "All countries are going to need to either increase oil prices or find a way to ease the burden of subsidies," says Jakob. But the problem for governments is that citizens long used to paying pennies for gasoline may not see it that way.

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