Dr. Fatih Birol, the chief economist at the International Energy Agency (IEA), has said that a survey of 800 of the world's top oil fields shows that they are decreasing in production 6.7% a year -- double what was estimated in 2007. His agency is now forecasting peak oil for the planet in 10 years -- a decade earlier than previously expected.

In its first-ever assessment of the world's major oil fields, the IEA concluded that the global energy system was at a crossroads and that consumption of oil was "patently unsustainable", with expected demand far outstripping supply. Oil production has already peaked in non-Opec countries and the era of cheap oil has come to an end, it warned.

In most fields, oil production has now peaked, which means that other sources of supply have to be found to meet existing demand. Even if demand remained steady, the world would have to find the equivalent of four Saudi Arabias to maintain production, and six Saudi Arabias if it is to keep up with the expected increase in demand between now and 2030, Dr Birol said.