The Misunderstood History of CO2: The Science Behind Earth's Most Controversial Molecule with Peter Brannen
The Great Simplification with Nate Hagens
How much carbon do humans emit?
Peter states humans emit roughly 40 gigatons CO2 annually and discusses how oceans and forests absorb part of it.
Carbon dioxide (CO2) is often seen as the problematic byproduct of modern lifestyles that threatens our planet's stability – at least within conversations among environmentalists. But this perspective overlooks the fundamental role of CO2 in everything on Earth, from the food we eat to the houses we live in to our bodies themselves. Despite this reality, the carbon cycle as we know it has been interrupted in ways never before seen in Earth's history. How could understanding the deep history of CO2, as well as humanity's relationship with this controversial and vital molecule, help us prepare for the planetary changes ahead?
In this episode, Nate is joined by science journalist Peter Brannen, who reframes CO2 from an industrial pollutant to a miraculous substance whose critical role within the carbon cycle makes Earth habitable. Peter traces our planet's history through the lens of CO2, including mass extinctions, Snowball Earth events, and the surprisingly stable Holocene period that has cradled human civilization. Peter also addresses humanity's current impact on the carbon cycle, the complexity and resilience of Earth's ecosystems, and the challenges we face as we push climate systems we don't fully understand into unknown territory.
How is the carbon cycle unexpectedly connected to the origins of oxygen, dozens of major and minor mass extinctions, and even the beginning of civilizations? How do humanity's current CO2 emissions compare to those of Earth's past? And could understanding the deep time of geology inspire both cosmic wonder and precautionary action, subsequently pushing us towards better decisions for the future?
(Conversation recorded on September 23rd, 2025)
About Peter Brannen:
Peter Brannen is an award-winning science journalist and contributing writer at The Atlantic, with particular interests in geology, ocean science, deep time, and the carbon cycle. His work has also appeared in The New York Times, The Washington Post, Wired, Aeon, The Boston Globe, Slate and The Guardian among other publications. His book, The Story of CO2 is the Story of Everything, was published earlier this year by Ecco, who also published his previous book, The Ends of the World, about the five major mass extinctions in Earth's history.
Peter was a 2023 visiting scholar at the Kluge Center at the Library of Congress, and is an affiliate at the Institute of Arctic and Alpine Research at the University of Colorado-Boulder. He was formerly a 2018 Scripps Fellow at CU-Boulder, a 2015 journalist-in-residence at the National Evolutionary Synthesis Center at Duke University, and a 2011 Ocean Science Journalism Fellow at the Woods Hole Oceanographic Institution in Woods Hole, MA. His essays have been featured in the Best American Science and Nature Writing series and in The Climate Book by Greta Thunberg.
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