(The one problem with this analysis is that, doing the division, we don't run out of fossil fuel for another 800 years. Of that "oil" is a subset of "fossil fuel" and seems to be generally believed to last less long; that same Wikipedia article estimates 57 ZJ (0.057) YJ of oil left, consuming 0.18 ZJ/year, giving 317 years of oil left. That still kind of says that, particularly if you don't believe that global peak oil is imminent, there's lots of time.)