Aeronaut wrote:
The question thus becomes “how long will fossil fuels (not the wells) be economically viable?”
this is probably a function of price of the cheapest one: coal.
estimated world coal reserves
“At the end of 2006 the recoverable coal reserves amounted to around 800 or 900 gigatons.”
— http://en.wikipedia.org/wiki/Coal#World_coal_reserves
