Wikipedia claims those estimates are obsolete, and the new ones are an order of magnitude smaller: https://en.wikipedia.org/wiki/Methane_clathrate#Reservoir_si

Wikipedia claims those estimates are obsolete, and the new ones are an order of magnitude smaller: https://en.wikipedia.org/wiki/Methane_clathrate#Reservoir_size https://en.wikipedia.org/wiki/Methane_clathrate#Reservoir_si... In which case the largest fossil-fuel resource is coal.