For decades, doomsayers have wailed that we are running out of oil, and economists have replied smugly that price rises would always bring forth extra supply. A new report from the consultancy, Wood Mackenzie, suggests that both may be right and that will lead to some difficult choices.

Wood Mackenzie’s report identifies 3,600bn barrels of unconventional reserves such as oil shales and sands. This is a colossal figure: current global oil consumption is about 30bn barrels a year. Better, these reserves are widely dispersed, with large resources near consumers in North America and China. They offer reassurance against the depletion of conventional oil and against instability in the Middle East.