[3] Stored solar energy is how one can think about all types of fossil fuels. Plants convert solar radiation (light) energy into chemical energy through photosynthesis. Layers of plant matter build up and, throughout millions of years, it converts into coal, oil, and natural gas.
It is noteworthy to point out that in 2011, 474 exaJoules of energy was used by the first world, or about 2 billion people – depending on how one defines the first world. This is equivalent to 449 quadrillion BTUs, representING all forms of energy combined (coal, oil, gas, nuclear, hydro, etc.). This is roughly equivalent to 15 billion tons of coal. If we wish to bring the other 5 billion people up to a first world standard of living, we would need to increase this energy production rate by three to five times, ignoring any advances in efficiency. If we wish to increase the standard of living beyond that of where the first world is today, bringing the energy per capita for everybody on the earth to twice that of the present level in the United States, we might need 10 times this rate of energy production. Achieving this with fossil fuels would be challenging to say the least. Even if one does not believe in climate change, consuming fossil fuels at 10 times the present rate should, at least, make one rethink that position.