When leaders from the Group of Eight nations agreed last week to cut carbon emissions in half by 2050, all the commentary debated their failure to set shorter-term goals.

But all of that chatter ignores the iceberg in the room: How will those nations or any others meet even that relatively modest goal? The scientific community argues that by 2050, carbon emissions must be reduced 80 percent below the level in the year 2000, if serious global warming is to be averted. I would argue that the political reality of today makes either of those goals impossible to reach. To succeed, many of the world's dictators and despots would have to agree to give up their holds on power.

About 80 percent of the world's human-generated carbon emissions result from burning fossil fuels — petroleum, natural gas, coal. More than half of that is fuel for cars. With gasoline prices at record levels, oil consumption in the United States and many other industrialized nations has fallen by about 4 percent this year. Still, the world's overall consumption of gasoline is increasing.

How can that be? Well, more than half of the world's people live in countries that subsidize gasoline — by as much as 97 percent. In those places, there's no incentive to conserve. Quite the opposite, in fact. And yet, no one can debate that it will be impossible to address the climate-change problem effectively without dramatically reducing gasoline consumption.

Working in Egypt last month, I hired a driver to take me north to the Nile River Delta. When he stopped for gas, I reached for my wallet to pay, not sure I had enough cash. But then I saw the gas price: the equivalent of $1.29 a gallon.

In Venezuela, gasoline costs just 12 cents per gallon. That's extreme. But in Russia, the price of gas is 20 percent less than in the United States. China just reduced its gas subsidies. Still, gas there costs about $3.40 a gallon.

Most of the nations that subsidize gasoline are totalitarian states, including Egypt, Iran, Cuba, China, Libya, Syria, North Korea, Turkmenistan, Sudan. Most of these dictators must maintain a careful balance of benefits for their people to stave off unrest that could oust them from power. Remember what happened last summer when Burma raised fuel prices? A vast popular uprising that brought the world's wrath raining down on the ruling junta.

Egyptians have rioted this summer over the rising cost of bread. Hosni Mubarak, the Egyptian president, responded by raising public-employee salaries by 30 percent. He had little choice. Meantime, Cairo's streets are clotted with cars, all of them honking at the same time. The traffic is as tangled and congested as any place on Earth.

If Mubarak were to end fuel subsidies, no doubt the entire nation, 82 million people, would turn against him.

The Chinese dictators' compact with their people requires the government to foster economic development. It's working, and one result is that Chinese buy about 25,000 new cars every day. What would happen if China suddenly ended the gas subsidy? In Astana, Kazahkstan, dictator-President Nursultan Nazarbayev lives in a marble palace atop a hill. Standing on his vast balcony, he likes to look out over his dominion. How long would his people put up with him if he suddenly required them to pay full price for gas? Now, it costs about $2.90 a gallon.

Around the world, fuel subsidies help dictators maintain their hold on power — global warming be damned. But even in democratic states, the idea of reducing gasoline consumption by close to 80 percent seems farfetched, particularly since the world's population is expected to increase by 50 percent by mid-century.

Right now, most Americans consider global warming a well-argued hypothesis, not necessarily a hard and fast fact. It's difficult for any government, democratic or despotic, to ask its people to sacrifice for something theoretical, and decades off, when holding on to power depends on effectively addressing today's serious problems — war, crime, education, health — right now.

Writing in Scientific American magazine, Jeffrey Sachs, head of Columbia University's Earth Institute, put it this way: "Even with a cutback in wasteful energy spending, our current technologies cannot support both a decline in carbon-dioxide emissions and an expanding global economy." Sachs and others believe technology will be the solution. We all can hope for important technical breakthroughs because most of the world's leaders will not make it their priority until the water is lapping at our feet.

Joel Brinkley is a Pulitzer Prize-winner and a professor of journalism at Stanford University. He wrote this commentary for McClatchy-Tribune Information Services.

We can talk about reducing consumption, but it remains farfetched nonetheless

More than half of the world's people live in countries that subsidize gasoline — by as much as 97 percent. In those places, there's no incentive to conserve. Quite the opposite, in fact. And yet, no one can debate that it will be impossible to address the climate-change problem effectively without dramatically reducing gasoline consumption.

Joel Brinkley is a Pulitzer Prize-winner and a professor of journalism at Stanford University. He wrote this commentary for McClatchy-Tribune Information Services.