As of 2020, the world has emitted a total of 1.7 trillion tonnes of CO2. Every year, we add an additional 40 billion tonnes to this number. The majority of these emissions come from China, the USA, and the European Union, as these regions produce the most GDP. However, other countries are quickly catching up.
The exact amount of CO2 that remains in the ground and could potentially be used is unknown, but it’s likely to be substantial. What we do know is the amount of fossil fuels that are recoverable with certainty, both technically and economically, and are listed on the balance sheets of countries and companies. If we were to use (burn) all of these resources, this is what we would end up with:”
Coal – 2.6 trillion tonnes of CO2. We have around 1.07 trillion tonnes of coal in its various shapes. Astonishingly, when coal is burned, it produces on average 2.4 times more CO2 than it weights. This is because coal is mostly carbon, and a single carbon atom attracts two oxygen atoms from the atmosphere to form CO2. If we burn all of that coal, we get 2.6 trillion tonnes of CO2.
Oil – 0,5 trillion tonnes of CO2. Each barrel of oil produces 2.3 times more CO2 than it weights. It’s better than coal because there is less of carbon in oil, and more hydrogen. More hydrogen is good, as this also means that the same amount of oil has nearly twice the energy as black coal. Current oil reserves are estimated at 236 billion tonnes / 1740 billion barrels, equivalent to 0,5 trillion tonnes of CO2.
Natural gas – 0.4 trillion tonnes of CO2. Approximately 2kg of CO2 for each cubic meter of the total 188 trillion cubic meters currently underground. Natural gas has even more hydrogen than oil and therefore more energy. It also burns more cleanly than oil.
Total CO2 “under the ground” – 3,5 trillion tonnes, which is the number you can get if you just search the search the internet. Anyway, at present rate we can go for 50 years before oil and gas run out, and then another hundred years before all coal ends. Likely we can go far more, because, as new technologies became available, and fossil fuel prices go up, more fuel can be extracted economically.
What does that mean
If we burn roughly one third of the reserves currently under the ground (reserves, not all resources!), there is a 50% chance of reaching temperature increase of 2oC. With the same fossil fuel use as today, we will arrive there in 30 years, likely before 2050. And we we burn all of it, we might be pushing 4-5 degrees warming.