Steve and Corey talk to Klaus Lackner, director of the Center for Negative Carbon Emissions (CNCE) at Arizona State University and the first person to suggest removing CO2 from air to address climate change. Steve asks whether Klaus’ research was motivated by a tail risk of catastrophic outcomes due to CO2 build up. Klaus explains that he sees atmospheric CO2 as a waste management problem. Calculations show that removing human-produced carbon is energetically and economically viable. Klaus describes his invention, a “mechanical tree”, that passively collects CO2 from the air, allowing it to be stored or converted to fuel.