All of recorded human history has happened during a period in which the average global temperature didn’t change by more than 1 degree Celsius. But the burning of fossil fuels has triggered a temperature rise projected to exceed 3 degrees by the end of the century. It will be catastrophic. But it can be avoided if we massively scale back the burning of fossil fuels. The US isn’t the biggest emitter of carbon dioxide in the world, but it’s emitted more carbon dioxide in total than any other country. So the US has an important role to play in global decarbonization; the world basically can’t get there without the US’s full participation. But the current US president doesn’t have any plans to do that. His Democratic challenger in the 2020 election, Joe Biden, does. Biden’s plan is ambitious: Its goal is to completely transition the US to clean energy by 2050. But his plan doesn’t get into the details of exactly how that will happen. For that, we talked to physicist and engineer Saul Griffith, who took us through his incredibly detailed road map for how the US could actually walk away from fossil fuels in the next 30 years.