But "proven reserves" are a function of technology and price not of how much oil there is. Many mineral reserves prove to expand faster than consumption.

@matt_black Which is why that end date tends to get moved up from time to time as improvements in technology and increased demand make hitherto unviable deposits desirable, but ultimately what doesn't change is that we're consuming fossil oil much, much, much faster than it's generated by the ecosystem, so eventually we will run out.

@jdunlop the necessary 'sea change' has already begun in UK. The above answer shows there is enough coal for 130 years, yet all the deep coal mines and all the open cast mines here have shut. By 2023 coal as a domestic fuel will be unavailable. The few remaining coal fired electricity generating stations will close by 2024. And new fossil-fuel cars will be gone by 2030.

Will they have heritage volunteer organizations reopen the coal mines like they do for the canals and the historic railways, to dig enough coal for the narrowboats and heritage steam engines? Or will they be literally bringing coal to Newcastle?

@Harper-ReinstateMonica There are about 6,000 registered narrow boats in use on UK canals, but the number of coal fired (and steam powered) boats that are actually used (i.e. not just displayed in museums) can probably be counted on the fingers of one hand. Heritage steam trains are increasingly problematic to operate aside from fuel considerations, since even if their top speed is high their acceleration is too slow to mix with modern commercial rail traffic without disrupting timetables. Importing one train-load of coal per year from say eastern Europe isn't going to destroy the planet!

@WeatherVane In many parts of the UK, coal has been gone as a domestic fuel for decades already. The first UK Clean Air Act restricting coal usage was passed in 1956.

@Harper-ReinstateMonica "Or will they be literally bringing coal to Newcastle?" The UK has been doing that for decades already. See statista.com/statistics/370921/…

So is your answer "pretty close for oil and gas, but way off for coal?"

@LShaver In my view, the numbers speak for themselves; there seems to be significant discrepancies between what the article claims and what you get applying the same methodology using IEA numbers.

@Dave I tend to agree, but this answer would benefit from a direct, clear response to the question.

@WeatherVane: "but we're not really going to wait until then to find alternative energy sources are we?" We've been looking for alternatives for a long time, and nothing comes close to petroleum. It's "free" (i.e. already available in the ground, unlike electricity or hydrogen), it's a liquid at ambient temperature and pressure, it's easy to store and transport, and it has a huge energy density. Too bad it's finite and it has a large impact on climate change.

@EricDuminil petroleum isn't free. It has to be extracted, shipped, refined, and shipped again. The energy efficiency for fossil fuel engines is less than 50%. It's a far bigger problem than just finding an alternative: it is political and economic too. Also 13% of the world's population have no access to electricity, and 40% do not have access to clean fuels for cooking: they lack infrastructure. Some economies are still huge consumers of coal, particularly China and India.

@WeatherVane: Indeed, that's why I wrote quotes around "free". Still, the energy return on investment is about 20:1 for oil. You only need to invest 1kWh in order to get 20kWh of oil. For hydrogen, the EROI is 1:4, i.e. a net loss. For biofuels, the EROI is often too close to 1 to be useful.

@EricDuminil so you are saying: petroleum is "too good" to do anything but wait until it is exhausted? Entire economies depend on oil: doing nothing will be easy.

@WeatherVane Basically, I'm saying that we're screwed. As you said, our entire economies (including food supply) depend on available cheap oil. We'll have to stop some day, the sooner the better. But we have no idea how to do so, or we don't accept the harsh implications of a life without all the energy slaves working for us.

@EricDuminil Your EROI calculation only works because current legislation allows you to set the cost of waste disposal at zero. If we factor in the true cost of fossil fuel waste products, like we do with nuclear power, oil, gas and coal become much less efficient. [In case you're in any doubt, I'm talking about CO2 here].

@OscarBravo: EROI only takes into account energy : how many kWh in and how many kWh out. EROI doesn't take waste (e.g. CO2) into account, Are you suggesting carbon sequestration? This would indeed require more energy, and would lower the EROI. But this technique also isn't proven to work well, or to work at large scale. Fossil fuels would indeed look much worse if we took waste into account, instead of simply releasing it to the atmosphere. But as one satirical party is asking in Germany : "Is it worth it to destroy the economy, just to save the planet?"

@EricDuminil If EROI is only about energy then it's just an arbitrary physical property of petroleum, like density or specific heat capacity, and has no value in calculating the economic worth of the product. If you want to make an economic argument for oil, you have to factor in the cost of re-building New Orleans, flooding Central Germany and burning California every decade or so.

@OscarBravo yes, more externalities should be taken into account for every energy source, including fossil fuels. But there's nothing arbitrary about energy in general, or EROI in particular. This ratio tells you if a proposed solution conflicts with the first law of thermodynamics. If it does, no amount of money will make it work. The economy is built on top of our physical world. It will be a very painful lesson when people finally realize the difference between economic theory and physical laws.