Compared to oil, natural gas is so abundant it's staggering. Proven petroleum reserves are good for another one trillion barrels or so. At today's rate of consumption, they will last about 40 years. Add in oil reserves thought to exist but still undiscovered, and the timeline stretches out some 160 years.

Known reserves of natural gas, which is composed mainly of the simple hydrocarbon methane, will last for about 50 years at today's consumption rate. Estimates of likely but as yet undiscovered gas resources extend that projection to about 200 years. But when the natural gas thought to lie buried deep under the ocean in methane hydrates is added in, the potential is mind-boggling. Hydrates, ice crystals that trap methane molecules, form below a depth of 300 meters as a result of methane-producing bacteria. Very little is known about how much gas is bottled up in these crystals or how to get it out, but best guesses are that the reserves could, even with natural-gas consumption rates doubling over the next several decades, last tens of thousands of years.