THE CONQUEST:

By the end of the 19th century, traditional biomass fuels (wood, charcoal, and straw, which together dominated energy use for millennia) were reduced to a small fraction of overall energy supply as coal became the principal fuel. The shift away from coal to hydrocarbons (crude oil and natural gas) began slowly before 1900 in the United States and Russia, and it accelerated only after World War II. By 1970, crude oil supplied 46 percent of the world's energy and its shares were 43 percent in the United States and 50 percent in Europe. There is no mystery about what will come next: Rising consumption of natural gas will eventually make it not only more important than crude oil but the single-most important fossil fuel.

Seen from this perspective, American shale gas production must be viewed as only one, albeit a major, component of gas's global rise. In 1970, natural gas supplied 18 percent of global commercial energy and that share rose to about 24 percent by 2010 (with the EU share going from less than 8 percent to 26 percent), while the worldwide crude oil share fell from 46 percent to 34 percent (and in the EU from 50 percent to 38 percent). Natural gas's rise has been slowed recently by China's extraordinarily high coal extraction rates, but these cannot be repeated in the future (the country is already a large importer of coal). Natural gas will thus continue its conquest of global and national energy supplies, with five factors behind the rise--discoveries of new large fields, diffusion of shale gas production, expansion of LNG exports, high prices of crude oil, and unrivaled efficiency of gas converters.

New giant gas fields have been discovered in such previously unpromising places as the Mediterranean off Israel's shores and deep Atlantic waters offshore near Brazil. There are extensive deposits of gas-bearing shales in Europe (particularly in Poland) and enormous resources in Asia. Recent reductions in the cost of gas liquefaction coupled with increased sizes of LNG tankers (they now rival the size of ships carrying crude oil) made LNG into a trade equivalent of oil: It can now be transported to consumers on any continent, bought without restrictive long-term contracts, and delivered at increasingly affordable prices. The totals speak for themselves: Global LNG trade rose roughly eightfold between 1980 and 2010, and it now accounts for 30 percent of the worldwide natural gas trade.

Little has to be said about high oil prices (the price spread between liquid and gaseous hydrocarbons has reached an unprecedented level), but the conversion efficiencies achievable by furnaces and turbines burning natural gas are not sufficiently appreciated. New, super-efficient household gas furnaces convert up to 97 percent of the fuel into heat; combined-cycle generation (using the waste heat from a gas turbine to raise steam and generate more electricity in an associated steam turbine) now produces electricity with 60 percent efficiency (and 70 percent will be possible in the future).

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