Fossil fuels are the main source of energy in the world, powering much of modern civilization as we know it, from transportation to industrial applications. But, as finite resources, this paradigm can't obviously last forever.
Considering our lives currently hinge on the availability of oil, coal, and gas, and will continue to do so for the foreseeable future given the rapid, but not fast enough adoption of renewable energy, all of this begs the question: how long before we run out?
This is a complex question is no straight answer because the availability and consumption of fossil fuel reserves are in constant flux. But the quick answer is that not too soon, as the goalpost has been constantly moving. In all likelihood, fossil fuels aren't about to run out during anyone's lifetime. In fact, there are now more available fossil fuel reserves than ever, despite record-high consumption with dire consequences for climate change.
Millions of years to make, only hundreds of years to spend
Fossil fuels have formed over an extensive period of time from the remains of plants and animals that lived millions of years ago. Humans have been using them in ample amounts since the 19th century and with our current rate of consumption, fossil fuel resources are depleting much faster than their regeneration potential, which is why they are "non-renewable".
In the 1950s, geologist M. King Hubbert predicted that the world will experience an economically damaging scarcity of fossil fuels. This idea has remained in the collective consciousness as the Peak Oil theory, according to which the production of oil, as a finite resource, will peak at some point and ultimately decline and deplete. According to some researchers, Hubbert included, Peak Oil is already behind us, and we are now living in a decline. However, more recent data seem to paint a different picture, where fossil fuel reserves have grown in abundance rather than experiencing a decline.
So, how long before we run out of fossil fuels? In order to project how much time we have left before the world runs out of oil, gas, and coal, one method is measuring the R/P ratios -- that is the ratio of reserves to current rates of production.
At the current rates of production, oil will run out in 53 years, natural gas in 54 years, and coal in 110 years, according to estimates from the 2015 World Energy Outlook study by the International Energy Agency. This forecast is predicated on the assumption that fossil fuels will constitute 59% of the total primary energy demand in 2040, even despite aggressive climate action policies.
Other researchers, organizations, and governments have different deadlines for fossil fuel exhaustion, depending on the data and assumptions that they make, as well as political affiliation and interests.
The American Petroleum Institute estimated in 1999 the world's oil supply would be depleted between 2062 and 2094, assuming total world oil reserves at between 1.4 and 2 trillion barrels. But in 2006, the Cambridge Energy Research Associates (CERA) predicted that 3.74 trillion barrels of oil remained on the Earth -- three times the number estimated by peak oil proponents.
So depending on who you ask, you may get widely different estimates for fossil fuel reserves. However, everyone seems to agree that we still have at least many decades before these resources run out even with today's voracious consumption of energy.
Is Peak Oil behind us? Doesn't look like it. Reserves are actually increasing!
While we know for sure that the exploitation of fossil fuels is limited, estimates can vary wildly because new deposits are sometimes found and new technology enables access to previously untapped oil or gas fields or allows more efficient extraction. So, the challenge in estimating a timescale for fossil fuel depletion lies in the fact that new resources are added fairly regularly. Therefore, we have to keep in mind that all of these estimates are based on R/P ratios and thereby only consider proven reserves, not probable or possible reserves of resources.
"Proven reserves" or "known reserves" refers to quantities of fossil fuels that, according to proven geological and engineering information, exist in a certain region with a high probability and can be extracted under existing economic and geological conditions. In reality, as technology improves, the quantity of proven reserves should only improve as we become better at extracting fossil fuels or new resources are identified with new surveys.
In 1980, the R/P ratio suggested only 32 years of oil production from existing reserves. However, according to data from the BP Statistical Review of World Energy, the known oil reserves were 254% larger in 2022 compared to 1980, while natural gas reserves were 265% higher compared to the same period.
A 1977 report issued by the Energy Information Administration concluded that the United States could only access 32 billion barrels of oil reserves and 207 trillion cubic feet of natural gas reserves. But from then to 2010, the country extracted 84 billion barrels of oil (2.6 times more than the initial estimate) and 610 trillion cubic feet of gas (2.9 times the initial reserve estimate). What's more, reserves are growing. Today, the U.S. has increased the size of its reserves by a third since 2011 thanks to horizontal drilling and hydraulic fracking which enable access to oil and gas trapped in underground rock formations. Previously, it wasn't economically feasible to extract these resources.
As technology continues to improve, both governments and oil & gas companies will be able to access new reserves -- some that can't currently be exploited and others that are still unidentified.
Japan, for instance, is planning to one day extract methane from undersea hydrate deposits -- these types of deposits may contain more than twice the amount of carbon as all of Earth's fossil fuels. Elsewhere, climate change is opening corridors in the Arctic -- ironically due to warming facilitated by the burning of fossil fuels -- that enables the extraction of oil that was previously logistically impossible to undertake. It was the Russian company Gazprom that brought home the first barrels of oil from the Arctic in 2014, and more have followed since. Now, some 20% of Russia’s GDP and 30% of its exports come from these chilly lands.
Keep the oil in the soil
Some might fear that we'll run out of oil and coal before we get the chance to replace them with renewable energy, thereby triggering a planetary-wide collapse of human civilization. But that's an unlikely scenario. First of all, if we burn even 50% of the world's reserves, we're screwed. Forget about the prospect of not being able to turn the lights for a second, and think of greater perils: runaway climate change.
Despite having used only a small fraction of fossil fuels, the planet’s atmosphere is already around one degree Celsius warmer on average than it was prior to the Industrial Revolution. A 2016 study published in Nature Climate Change assessed what would happen if we burned all the fossil fuels known to exist on Earth.
Assuming a scenario where there are no efforts to curb global warming, by 2300 CO2 would stabilize at roughly 2,000 parts per million (ppm), five times higher than today’s level (~418ppm) — resulting in a total of 5 trillion tons of carbon dioxide finding its way into the atmosphere. In this nightmarish scenario, global average temperatures would be pushed by as much as 8 degrees Celsius past pre-Industrial levels, with the Arctic bearing the grunt of warming, experiencing temperatures rising by as much as 17 degrees Celsius.
As such, the limiting factor on humans' fossil fuel use is not the depletion of recoverable fossil fuels, but the crossing of a dangerous threshold past which the planet is no longer able to withstand the byproducts of burning fossil fuels.
According to a 2021 study led by researchers at University College London, nearly 60% of oil and fossil methane gas, and 90% of coal must remain unextracted to keep within a 1.5 °C carbon budget. Furthermore, scientists estimate that oil and gas production must decline globally by 3% each year until 2050 to meet this goal.
Knowing oil and gas won't ever run out in your lifetime shouldn't be an excuse to keep using them. Rather, knowing this, we should all take action to ensure that our children and grandchildren actually have a future.
This article originally appeared in 2018 and has been updated with new information.