Peak oil is the point in time when the maximum rate of petroleum extraction is reached, after which the rate of production is expected to enter terminal decline. Global production of oil fell from a high point in 2005 at 74 mb/d, but has since rebounded setting new records in both 2011 and 2012. There is active debate as to when global peak oil will occur, how to measure peak oil, and whether peak oil production will be supply or demand driven.
The aggregate production rate from an oil field over time usually grows until the rate peaks and then declines—sometimes rapidly—until the field is depleted. This concept is derived from the Hubbert curve, and has been shown to sometimes be applicable to the sum of a nation's domestic production rate, and similarly to the global rate of petroleum production. However, the discovery of new fields, the development of new production techniques and the exploitation of unconventional supplies can disrupt this correlation. Peak oil is often confused with oil depletion; peak oil is the point of maximum production, while depletion refers to a period of falling reserves and supply.
M. King Hubbert created and first used the models behind peak oil in 1956 to accurately predict that United States oil production would peak between 1965 and 1971. His logistic model, now called Hubbert peak theory, and its variants have been used to describe and predict the peak and decline of production from regions, and countries, and has also proved useful in other limited-resource production-domains. According to the Hubbert model, the production rate of a limited resource will follow a roughly symmetrical logistic distribution curve (sometimes incorrectly compared to a bell-shaped curve) based on the limits of exploitability and market pressures.
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 oil price increase—due to 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.
In 2008 oil prices reached a record high of $145/barrel. Governments sought alternatives to oil, particularly the use of ethanol, but that had the unintended consequence of creating higher food prices, particularly in the developing countries. Throughout the first two quarters of 2008, there were signs that a global recession was being made worse by a series of record oil prices.
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. These models show the price of oil at first escalating and then retreating as other types of fuel and energy sources are used. Pessimistic predictions of future oil production are that either the peak has already occurred, that oil production is on the cusp of the peak, or that it will occur shortly. In 2013 the International Energy Agency (IEA) projected that global oil production capacity would grow 8.4 mb/d over the next 5 years.
Global warming is the rise in the average temperature of Earth's atmosphere and oceans since the late 19th century and its projected continuation. Since the early 20th century, Earth's mean surface temperature has increased by about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980. Warming of the climate system is unequivocal, and scientists are more than 90% certain that it is primarily caused by increasing concentrations of greenhouse gases produced by human activities such as the burning of fossil fuels and deforestation. These findings are recognized by the national science academies of all major industrialized nations.