The vast majority of the world's fossil fuels are effectively "unextractable" and must remain in the ground if we want even half a chance at meeting our climate goals, according to a new study.
For nations like Indonesia and Australia, the world's leading exporters in coal, that will require abandoning 95 percent of their natural deposits come 2050, researchers at University College London have calculated.
In that same time frame, Middle Eastern nations will have to leave all their coal reserves in the ground and the United States will have to leave 97 percent of its stores untouched.
These are the regions that truly have their work cut out for them, but this is, of course, a team effort.
Across the world, nearly 90 percent of all coal reserves will need to stay in the ground over the next three decades, including 76 percent in China and India. Any more removal than that and this combustible black rock could easily push global warming over the 1.5 degree Celsius goal, scientists warn.
Nor is it just coal we need to worry about. At the same time we tackle this particular fossil fuel, the world must also halt 60 percent of its oil and methane gas extractions, including those projects that have already started.
Canada alone will have to leave 83 percent of its oil in the ground by 2050 and 81 percent of its fossil methane gas.
Even if the world can tick all three of those boxes – a colossal challenge to be sure – researchers estimate we have only a 50 percent chance of keeping global temperatures below the 1.5 degree threshold.
One of our best climate scenarios, it seems, boils down to the statistical toss of a coin.
The findings are a grim update to an already gloomy 2015 paper, which estimated nearly a third of all oil reserves, half of all gas reserves, and over 80 percent of coal reserves will need to stay in the ground by 2050 if we want to keep warming from pushing 2 °C.
The new estimates are considerably more challenging, adding 25 percent more oil reserves that will need to stay in the ground, as well as 10 percent more coal reserves that will need to remain untouched if we want to keep warming under 1.5 °C.
And in all likelihood, that's still too little too late. The model in the current study, for instance, does not take into account any possible feedback systems that may trigger a whole bunch of new carbon emissions sooner than we assumed.
What's more, if we want to give ourselves a greater than 50 percent chance of keeping to 1.5 °C, we will need to keep even more carbon in the ground.
"The bleak picture painted by our scenarios for the global fossil fuel industry is very probably an underestimate of what is required and, as a result, production would need to be curtailed even faster," the authors write.
Obviously, it's hard to predict what the future will look like. Some scientists think the rollout of renewables and the possibility of carbon capture could allow us to persist with using fossil fuels, at least to a certain extent, but this view remains highly controversial, especially since the technology we have has not yet been scaled up to the task.
The new model relies on a certain amount of carbon capture and removal by 2050, but right now some question if we can even achieve that.
After 2050, the authors say the only thing we should still be using fossil fuels for is aviation and feedstock for the petrochemical industry.
If a worldwide energy transition is not achieved by 2050, we will not only resign ourselves to a worse climate crisis, some nations could suffer huge losses of revenue.
At the moment, Middle Eastern nations, as well as Russia and other former Soviet states, are the largest fossil fuel reserve holders, which means they stand to lose the most.
In Iraq, Bahrain, Saudi Arabia, and Kuwait, for instance, fossil fuels currently account for between 65 and 85 percent of total government revenue.
If the fossil fuel bubble pops before these nations can transition to cleaner forms of energy, some could very well go bankrupt.
There's a lot at stake and there's no more time to dawdle. The authors argue nations around the world need to start drafting domestic policies that restrict fossil fuel production and reduce demand, whether it be through subsidies, taxes, bans on new exploration, or penalties for polluters.
It's imperative we find an economically viable way to keep fossil fuels buried in the ground, as that is now the only sure way to save lives and livelihoods.
The study was published in Nature.