For their calculations, the two assumed that where there was a gap between demand and conventional supply it would be filled with synthetic fuels, first with tar-sands oil and later with oil from coal and shale. (According to high-end estimates, coal and oil shale could together yield some ten trillion barrels of unconventional crude.) They then calculated what the impact would be on global carbon-dioxide levels.

NEWYORKER: Unconventional Crude

There is oil aplenty of other sorts (tar sands, liquefied coal and so on), so the stuff is unlikely to run out for a long time yet.

ECONOMIST: A survey of The future of energy

The greens may not be able to stop the Canadians from extracting oil from the Alberta tar sands, but they would succeed in wiping out American coal-fired power.

WSJ: Review & Outlook: Carbon Power Politics

Unconventional sources of oil and gas that are set for further exploitation include Canada's tar sands, shale and coal-bed methane deposits around the world.

ECONOMIST: Drilling on Wall Street | The