n. The peak of the Earth's oil production.
Peak oil, an event based on M. King Hubbert's theory, is the point in time when the maximum rate of extraction of petroleum is reached, after which it is expected to enter terminal decline. Peak oil theory is based on the observed rise, peak, fall, and depletion of aggregate production rate in oil fields over time. It is often confused with oil depletion; however, peak oil is the point of maximum production, while depletion refers to a period of falling reserves and supply.
Some observers, such as petroleum industry experts Kenneth S. Deffeyes and Matthew Simmons, predict negative global economy implications following a post-peak production decline and subsequent oil price increase because of the high dependence of most modern industrial transport, agricultural, and industrial systems on the low cost and high availability of oil. Predictions vary greatly as to what exactly these negative effects would be.
Oil production forecasts on which predictions of peak oil are based are often made within a range which includes optimistic (higher production) and pessimistic (lower production) scenarios. Optimistic estimations of peak production forecast the global decline will begin after 2020, and assume major investments in alternatives will occur before a crisis, without requiring major changes in the lifestyle of heavily oil-consuming nations. Pessimistic predictions of future oil production made after 2007 stated either that the peak had already occurred, that oil production was on the cusp of the peak, or that it would occur shortly.
Hubbert's original prediction that US peak oil would be in about 1970 seemed accurate for a time, as US average annual production peaked in 1970 at 9.6 million barrels per day. However, the successful application of massive hydraulic fracturing to additional tight reservoirs caused US production to rebound, challenging the inevitability of post-peak decline for the US oil production. In addition, Hubbert's original predictions for world peak oil production proved premature.