What Carbon Dioxide Has to Do With the Meaning of Life

How did life first form on Earth? What does entropy have to do with the origins of mammalian life — or the creation of the modern economy? And what chemical process do people, insects, Volkswagens, and coal power plants all share?

On this week’s episode of Shift Key, Rob chats with Peter Brannen, the author of a new history of the planet, The Story of CO2 Is the Story of Everything. The book weaves together a single narrative from the Big Bang to the Permian explosion to the oil-devouring economy of today by means of a single common thread: CO2, the same molecule now threatening our continued flourishing.

Brannen is a contributing writer at The Atlantic and the author of The Ends of the World, a history of mass extinctions on Earth. He is an affiliate at the Institute of Arctic and Alpine Research at the University of Colorado, Boulder. Shift Key is hosted by Robinson Meyer, the founding executive editor of Heatmap, and Jesse Jenkins, a professor of energy systems engineering at Princeton University. Jesse is off this week.

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Here is an excerpt from our conversation:

Robinson Meyer: Why do we have a surplus of oxygen in the air in the first place? It was, for me, also something I did not understand at all before I read the book.

Peter Brannen: So there’s this common trope that two out of the next three breaths you have is from phytoplankton the ocean, or a quarter of it is from the Amazon alive today. And there’s a sense in which that’s true because oxygen and CO2 are being exchanged very quickly in the biosphere. But there is something like 800 times more oxygen in the air than can be produced by the entire biosphere. And all of the oxygen that’s produced by the rainforest, say — the rainforest is a living system where everything else is consuming that organic matter and feeding off of it. And it’s kind of a wash — just as much oxygen is created by the trees as is consumed by the bugs and fungi and jaguars and all the things that are living in the rainforest that are feeding off those plants and respiring that plant matter back to things like CO2 and water. So on a net scale it’s a wash.

So that gets you a planet with close to zero oxygen, and instead we have this absurd abundance of this thing that wants to react with everything. And the only way you can do that is if, say, you imagine a tree and when it dies, rather than being decomposed by fungi and beetles and on and on, that tree suddenly gets buried in sediment and falls into the crust and becomes part of the rock record, and the oxygen it made in life is not used in its own destruction. And by shielding that tree in the earth, you leave this surplus of oxygen in the air. And over all of Earth history, as a vanishingly small amount of this organic matter, things like plants and algae, do make it into the rock record, they leave an equivalent gift of oxygen in the air as a surplus.

We are more familiar with plant matter in the crust where it’s economically exploitable — we call those fossil fuels. So in a weird way, the fact that me and you can breathe — I don’t think a lot of people attribute that to the fact that there’s fossil fuels in the ground. Luckily most, you know, quote-unquote fossil fuels are very diffuse in mudstones, and they’re not economically exploitable. And we’re never going to run out of oxygen by burning fossil fuels because, you know, we worry about CO2 going up in parts per million and oxygens in whole percent. So, you know, it is true that for every molecule of CO2 we burn we’re bringing down oxygen by an equivalent amount, it’s just not that concerning.

But yeah, there is this astounding way of reframing, of looking at the world where the plant surface is breathable only because of what’s happened in the rocks beneath it.

Mentioned:

Peter’s book, The Story of CO2 Is the Story of Everything

Lost City Hydrothermal Field

ATP synthase in action

This episode of Shift Key is sponsored by …

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Music for Shift Key is by Adam Kromelow.