I recalculated my world energy projections after finding an error in the timing for exhausting fossil fuel reserves, and came up with three different scenarios representing the best, worst, and mode cases (where the “mode case” represents the closest agreement between my assumptions). A PERT estimate was done using these scenarios to derive the most likely scenario. I also determined the associated population curves, based on curve fits of population vs. total cumulative energy use. The results, along with relevant assumptions, are shown on my Web site.
Based on the mode and best cases, the world’s petroleum supply will be exhausted by 2047, natural gas will run out by 2055, and the coal supply will be exhausted by 2157. The worst case has production drop to zero for all energy by 2037.
In all scenarios, the world’s population reaches a maximum in less than 20 years of about 7.1 billion people before either dropping or leveling out (the leveling out occurs with the “worst” case energy projection). The most rapid decline accompanies the “best” case, reaching zero population by 2048; this corresponds to my consumption model’s projection based on cumulative ecological footprint. The mode case projects a more gradual population decline, reaching zero by 2098. The expected case drops gradually and levels off at 2.1 billion people by 2097.