Is there a top in sight for the rally in oil prices?

Crude oil futures are up more than 20 percent so far this year, and today oil climbed to nearly $118 a barrel, with no sign that a major retreat may be near.

Much has been made of the speculative element in the rise of oil and other commodities, as investors around the world seek alternatives to equities and other investments. And certainly the weakness of the dollar is playing a role.

But the oil story is primarily one of demand—and by two countries in particular: China and India, the two most populous nations. Their economic booms are drawing off inventories even as the world's biggest economy, the United States, slows.

Jad Mouawad in a Week in Review article in the New York Times says supply problems may only get worse in the future.

"Consider a few numbers: The planet's population is expected to grow by 50 percent to nine billion by sometime in the middle of the century. The number of cars and trucks is projected to double in 30 years—to more than two billion—as developing nations rapidly modernize. And twice as many passenger jetliners, more than 36,000, will in all likelihood be crisscrossing the skies in 20 years."

The rise in oil today was triggered by number of events that underscored how nervous investors are about any disruptions to supply.

Several pipelines in the oil-rich delta region of southern Nigeria were reportedly blown up and a Japanese oil tanker was attacked off the coast of Yemen.

And the president of the Organization of Petroleum Exporting Countries indicated that the group would not raise its production quotas.

"The price seems to be rising inexorably towards $120,'' Bill Farren-Price, director of energy at Medley Global Advisors in London, told Bloomberg News. "OPEC has a very limited amount of spare capacity left, and maybe they're trying to keep that in case there's actual physical disruption.''

To be sure, things can quickly change in commodities. James Burkhard, managing director of Cambridge Energy Research Associates' global oil group, noted this in testimony earlier this month before the Senate Energy Committee.

"Just when the future seems preordained in the oil market, the unexpected can unfold. It did in the decade following 1998, just as it had several times since 1970. This year will be a stiff test for the new oil-price era that dawned on the world several years ago."