Despite prophecies that fossil fuels would soon run out, new reserves were discovered faster during the 1970's and 1980's than the old ones were consumed.

However the quality of the coal varies, the older the coal the higher its calorific value and the deeper it is found making extraction more difficult. For example brown coal is 23,000 years old and constitutes 62% carbon, anthracite is 32,560 years old and is 91% carbon.

In 1970, there were enough known oil reserves to last for 31 years; by 1989 however, this had risen to 41 years supply. There is also enough natural gas to last for about 60 years. It is not long really.

The USA has already burned 80% of all the oil so far discovered. It is spending hundreds of billions of dollars searching for new deposits and ways to break down the heavier oils. New reserves are increasingly being found in places where they will be difficult to exploit, and transport to where they are needed. The US Bush administration has given the go ahead to exploit Alaska more.