First, at a tree ring conference in the relatively treeless city of Tucson, Arizona, three scientists walk into a bar. The trio gets to talking, trying to explain a mysterious set of core samples from the Florida Keys. At some point, they come up with a harebrained idea: put the tree rings next to a seemingly unrelated dataset. Once they do, they notice something that no one has ever noticed before, a force of nature that helped shape modern human history and that is eerily similar to what’s happening on our planet right now. With help from pirates, astronomers and an 80-year-old bartender, this episode will change the way you look at the sun. (Warning: Do not look at the sun.) 

Then, we wrestle with the question of what we should be doing about climate change, or what we should even talk about. Summer 2023 was a pretty scary one for the planet. Global temperatures in June and July reached record highs. And over in the North Atlantic Sea, the water temperature spiked to off-the-chart levels. Some people figured that meant we were about to go over the edge, doomsday. In the face of this, Hank Green (a long time environmentalist and science educator behind SciShow, Crash Course, and more), took to social media to put things in context, to keep people focused on what we can do about climate change.

In the process, he came across a couple studies that suggested a reduction in sulfurous smog from cargo ships may have accidentally warmed the waters. And while Hank saw a silver lining around those smog clouds, the story he told—about smog clouds and cooling waters and the problem of geoengineering—took us on a rollercoaster ride of hope and terror.