For “Marketplace” host Kai Ryssdal, joining the Navy fresh out of college was one of the most consequential times of his life. It was the 1980s; the Cold War and the Soviet “evil empire,” in President Ronald Reagan’s words, was the greatest threat. Fast-forward through 40 years and one career change, and the threat looks different. Climate change does not have a face or a flag, but it will fundamentally change the way the U.S. military trains and fights. It already has. 

Our armed forces have a global presence and a huge carbon footprint. The Department of Defense consumes more than 85 million barrels of fuel per year. It is one of the biggest emitters of greenhouse gas in the world. It bears some responsibility for the climate crisis, yet it has to find ways to navigate a planet with more climate extremes and, potentially, more conflict.

In the sixth season of “How We Survive,” Ryssdal travels to far corners of the world, from a small Arctic village to a remote island in the Pacific and a warehouse in Brooklyn, New York. He shines a light on how the institution that shaped him could shape our climate future.