Oil and doomsday

Recently, I provided an estimate of the amount of oil that was formed in the Earth—about 18 trillion barrels.  It's always good to tackle these kinds of problems from different angles, and before using the composition of the atmosphere to do the calculation, I had planned to re-purpose the doomsday argument.  It seems much better suited to this type of problem.  After all, there is a finite amount of oil—or, rather, a finite number of barrels of oil—that we are drawing from.

However, before we are able to apply the doomsday argument, we need to know how many barrels of oil have already been consumed. Using data from Energy Trends Insider, it appears that approximately 1.4 trillion barrels have been produced in modern history.  That being said, reliable verifications of this estimate are hard to find.


Using the doomsday argument, we find that we can be 94% confident that there are at most 16.6 trillion barrels of oil remaining, given that we have already consumed 1.4 trillion barrels.

Peak oil, part II

"It is sunlight in modified form which turns all the windmills and water wheels and the machinery which they drive. It is the energy derived from coal and petroleum (fossil sunlight) which propels our steam and gas engines, our locomotives and automobiles." ― John Harvey Kellogg

In a previous post, I wrote about peak oil—particularly that answering the question of how much oil is left is not easy.  That said, a new approach has occurred to me.  Oil and coal are the remains of ancient plants, formed 300 million years ago in the carboniferous period—C on the horizontal axis of the chart below.  The periods leading up to this saw the proliferation of plants, which removed massive amounts of carbon from the atmosphere.  At its peak, carbon dioxide made up 7000 parts per million (ppm) of the atmosphere, but today makes up only 180 ppm.  This carbon went somewhere, and for the most part it was sequestered in rocks as coal and oil.  A simple calculation puts the weight of this carbon to be 10 trillion tonnes.

How much is oil and how much is coal?  Consider the proven reserves of oil versus coal.  There are 190 billion tonnes of oil reserves, but there are 860 billion tonnes of coal reserves.  Assuming that this reflects their natural abundance, we'll assume that oil and coal are in a ratio of 5 to 1 of sequestered carbon.  This implies that there have been 3.6 trillion tonnes of oil and natural gas—18 trillion barrels—and 11 trillion tonnes of coal.

How long will this last?  As of 2015, 93 million barrels of oil are consumed per day—about 34 billion per year—which has grown by about 1% per year since the 1980s.  If this continues, there are 185 years of oil.  That being said, consumption must eventually stop growing and begin to decline—that is the notion of peak oil.  Instead, oil rations will eventually be put into effect, which could mean that oil will be here for centuries.  As for coal, 7.5 billion tonnes are consumed per year, growing by about 2% per year since the 1980s.  This implies a 170 year supply.  The same caveats apply.  Many things can change in this time, too.  It's still hard to say how long we will burn fossil fuels.

Peak oil

"Life without oil, in fact, would be so different that it is frightening to contemplate. We are addicted, and it is no comfortable addiction. Like other drugs, oil comes with a baggage of greed, crime and filth. Worse, it is smothering the planet."  ― James Buchan

Petroleum is a non-renewable resource. The question we need to ask is just how much is left?  A 2013 OPEC report estimated that there are 1.5 trillion barrels of oil in proven reserves in the world.  At the rate the world consumes oil, this will be gone in only 44 years.  In 2014, BP released a report putting the figure at 1.7 trillion barrels, claiming that this will last 53 years.  New oil is continually being discovered, though—oil companies have an incentive to find these new resources.  How long we can keep discovering new oil, however, isn't clear.

Source data via OPEC.

Understanding this chart is difficult—not what it says, but why it says it.  This requires a more detailed study of the history of oil production and the technologies that have driven discovery.  In the past, intermittent bursts of discovery seem to have been the norm.  This appears to have changed in the 1990s, with a lull that has lasted until the present—I am most interested in finding out why.  However, the size of the earth is finite.  The oil we have already found is low hanging fruit—the remaining oil will be difficult to find.  In addition to slowing rates of discovery, the oil industry will also face increased competition from alternative energy and—one may hope—increased pressure from the public for environmental responsibility.  It is likely that the end of oil will not come from dwindling supplies, but from these other causes.