Current sources of fossil fuels, i.e. oil, natural gas, coal, oil sands and oil shale, are mixes of hydrocarbons which have been formed from dead organic matter over millions of years through geological transformation processes. Since no new fossil fuels can develop within time frames relevant to human existence they are designated as non-renewable forms of energy.
Forecasts for the statistical lifetime of individual fossil fuel reserves vary considerably. These depend on assumptions concerning the development of global demand and supply, proven technically and economically recoverable reserves, and resources (proven or presumed reserves of energy sources, the exploitation of which is currently not technically and/or economically viable). Price levels play a decisive role in this context too. Evidence of this is the boom in shale gas and shale oil in the USA and Canada since the middle of the first decade of the 21st century. The exploitation of these hitherto barely tapped reserves with expensive fracking extraction technology was only possible after the oil price had exceeded the 50 dollars per barrel mark for the long term. Assuming that the consumption of fossil fuels remains stable at current levels, proven oil reserves are expected to last at least 53 years according to the statistics compiled by BP. BP also forecasts approximately 55 years for gas and more than 100 years for coal.
Nevertheless, most specialists and organisations assume that the demand for fossil fuels will decline in the coming decades owing to technical progress in renewable energy and climate policy objectives. Almost all countries have undertaken to reduce CO2 emissions in line with their obligations in the context of the Paris Agreement. Switzerland aims to achieve climate neutrality by 2050.
The annual report on monitoring Energy Strategy 2050 also makes forecasts for the development of the international fossil fuel markets (in the chapter on the international environment).