But there is another school of thought, which believes in the concept of Peak Oil. As a global concept, it is an extension of the (correct) prediction made by geophysicist King Hubbert in 1956 that US oil production would peak around 1970, even with the most optimistic view of likely reserves. Others have previously questioned the likelihood of IPCC assumptions on fossil fuel use being right, but Prof David Rutledge of Caltech has analysed the situation in some detail. (Readers can access Prof Rutledge's lecture and slides at http://rutledge.caltech.edu/ and form their own opinion.)
Not only does he conclude that exploitable global oil reserves are finite, but he questions the prevailing view that there are sufficient coal reserves for well over a century (indeed, unlike oil, proven coal reserves have fallen over recent decades). He estimates total exploitable reserves of oil, gas and coal at 938 Gtoe (gigatonnes oil equivalent). On that basis, we have already used about 40% of the total, and 90% of total resources would be exhausted by 2068.