"Peak oil" -- what is that? The concept has been discussed since 1949, when geologist M. King Hubbert theorized that the extraction of the black gold followed a simple bell curve, meaning that after passing the peak in the curve, extraction would decline. After peak, never again would we be able to extract, and use, as much oil as we had previously.
In 1956, Hubbert made a startling and controversial prediction: America's oil production would peak in or around 1970. Hubbert's peers were confounded, as it was inconceivable that the United States, the world's largest oil producer in the first half of the 20th century -- literally the "Saudi Arabia" of the West -- could possibly decline in production.
So Hubbert was ridiculed, that is, until soon after 1970, when it became obvious that U.S. production had indeed peaked that year. (Peaks in production, whether in individual oil fields or oil nations, or worldwide, are only recognizable in hindsight, by comparing production in subsequent years.)