What Would Happen if We Burned All the Fossil Fuels?

Picture bogs swarming with plant-life, oceans teeming with life, dinosaurs roaming the Earth. Picture those plants and animals dying, and over the course of 300 million years, becoming coal, oil, and gas through a complex series of processes beneath the soil. Fast forward to the present and now see the vast, Earth-wrecking machinery extracting those dead plants and animals to power our economy.

How much longer can we keep this up for? Did enough plants and animals die in the ancient past to sustain our current levels of fossil fuel consumption forever? What happens if we blow through all the fossil fuels available this century, unleashing a glug of carbon dioxide into the atmosphere the likes of which the planet has never seen?

It would be somewhere between super bad and sublimely screwed if we did that. The world hasn’t exactly shown much appetite to curb fossil fuel use. That’s not say the world will keep going down that path, of course. But this is Giz Asks, and we’re here to ask the weird questions and get down to the nitty gritty. So we posed the question to a number of experts in engineering, physics, climate modeling, and paleoclimate of what would happen to the climate—and society—if we kept our fossil fuel bender going down to the last drop .

Sarah Carmichael

Professor of geochemistry, Appalachian State University and National Geographic Explorer

The first thing to consider is timescales. If we burned all the fossil fuels, the amount of carbon dioxide put into the atmosphere in such a short amount of time would be unlike anything that has happened in Earth’s history. Even the end-Permian extinction (where 96% of life went extinct) is not really analogous. The end-Permian was due to massive volcanism, and likely this process was the equivalent burning of lots of fossil fuels, because the the location of the volcanism was also one with a lot of buried coal and natural gas deposits; the magma essentially cooked them away and released carbon dioxide into the atmosphere in the process. But the end-Permian took a very long time to happen, at least if we think about it on human timescales. In geologic time it was relatively rapid, at around 200,000 years or less. But it has only been about 200 years or so at a maximum that we’ve been burning fossil fuels on Earth and already we see the effects on climate.

However, one of the things that makes comparisons to deep time pretty complicated is our current continental configuration and where major mountain chains are located. When other major mass extinctions have happened in the past, our continents have been in very different positions. We have had the supercontinent Pangaea either forming, present, or breaking apart. There were completely different ocean currents due to continental boundaries. When continents are all clustered together, bad things can happen in terms of climate extremes.

One of the other complicating factors is sea level as it interacts with topography. For example, in the Late Devonian – a time period characterized by the transition from a greenhouse to an icehouse climate and another one of the major mass extinctions in Earth’s history) – we continental topographies that supported lots of inland, shallow, restricted seas. There are not really analogues to these seaways in the modern continental configuration.

The way our continents are configured now, we are probably a bit more protected from catastrophic climate change than we would be if our continents were in a different position. But again, we are in totally uncharted territory in terms of the rapidity and rate of carbon dioxide emissions, so I can’t predict a concrete scenario here.

Abigail Mechtenburg

Assistant Teaching Professor of Physics and Physics Laboratory Co-Director at the University of Notre Dame

I work on something that tends to get ignored: electricity failure in hospitals in low-to-middle income countries. When fossil fuels are no longer available—especially if it happens abruptly, which it potentially will—we’re going to see patients dying in hospitals and healthcare facilities due to electricity failure, and this will be particularly acute during natural disasters.

Currently, the World Health Organization has no specific policies for how to address electricity failures. Large percentages of the population are already facing fossil fuel shortages. They have healthcare, but because electricity fails and diesel and gas are too expensive, patients die. Why is this happening? It’s not due to a shortage—it’s because fewer fossil fuels in the ground have led to higher prices. They’ve recently gone down, of course, but even at their current prices there are countries struggling to get it for their hospitals.

Running out of fossil fuels will also seriously impact transportation. The only reason we’ve been even halfway able to survive through covid-19 is that we can ship things. If all of a sudden we can’t fly the way we do now, our global economy will be constrained to a semi-local condition.

Will all this happen? It depends on human choices. But we also have to live with a serious degree of uncertainty—we can’t know. That said, I do know for sure that in a hundred years we’re screwed.

Edward S. Rubin

Professor of Engineering and Public Policy and Mechanical Engineering at Carnegie Mellon University

The quick (somewhat glib) answer to your hypothetical question is that we’ll never completely run out of fossil fuels, because that last barrel of oil, cubic foot of gas, or ton of coal would be too expensive and thus stay in the ground! Instead, we would turn to other available energy sources like renewables (wind, solar, hydro, biomass, etc.) and perhaps nuclear. If energy supplies were limited for whatever reason, energy demands would have to adjust to meet available supplies in that hypothetical world, and the available energy would be used a lot more efficiently.

Jessica Kaminsky

Assistant Professor, Civil and Environmental Engineering, University of Washington

We will eventually shift to renewable electricity; we do not have another option assuming we want the human species to continue to exist (see: climate change), and assuming that we don’t care to do without lights and the internet and etc, etc. The answer to the question of what happens when we stop using fossil fuels (likely because we decide either the environmental or economic cost is too high) depends on when this happens, or more precisely how much technology has advanced by then. Specifically, we still need advances in batteries and storage, because wind and solar generation isn’t always available on demand, and existing storage technologies are still expensive.

If we stopped using all fossil fuels sooner rather than later, we would have to decide if we want to accept higher electrical prices or lower electrical reliability. If we can live with the lights being mostly but not always working in much of the grid, we don’t need to invest as much in expensive storage. In that case, places like hospitals or research labs that cannot accept any reduction of reliability in electricity could pay for microgrids to supplement the larger grid they exist in. However, many or even most people assume that lower reliability is not a politically viable option. Another question is if society would consider nuclear power for electrical generation. Personally I don’t care for nuclear because I believe the risks of catastrophic failures and waste management are too high, but there are plenty of people who disagree with me and think of it as an underutilized and carbon-efficient (no direct carbon emissions) electrical resource.

To my mind, the more interesting or at least more timely question is, what happens when we stop using so much fossil fuel to generate electricity. For example, in the US we are already at a point technologically where a very large percentage of our electricity—something like 80%—could be coming from renewables. The cost effectiveness and reliability of this is also pretty decent, especially if we can meet a very small percentage of the total electrical demand with different technologies. And this financial argument for renewables will only get stronger as costs for solar continue to plummet—it is already the low cost option, without subsidy, in some markets.

Ken Caldera

Emeritus Senior Scientist, Global Ecology, Carnegie Institution for Science

There are 1,000,000 billion tons of reduced carbon in Earth’s sedimentary shell, so we will never run out of fossil fuel. It is just that eventually the amount of effort that you have to put into extracting the carbon gets bigger than the amount of benefit you get from burning that carbon.

There is an abundance of wind, solar, and nuclear energy. With enough electricity, fuels can be synthesized taking hydrogen from water and carbon either from plants or directly from CO2 in the atmosphere. These carbon-neutral fuels can be used for long-haul jets and other applications that require very dense energy storage.

I don’t see running out of fossil fuels as a problem. Maybe the bigger problem is that we are not running out of fossil fuels fast enough to protect us from dangerous climate change.

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