wo years ago, the crew of the Po- larstern, a German icebreaker frozen into Arctic sea ice, shot a green laser up into the night. The beam’s reflected light was meant to help researchers study icy winter clouds. Instead, the beam encountered something unexpected: a kilometers-thick layer of particles in the stratosphere, more than 7 kilometers up. The haze, the researchers later concluded, was smoke from enormous wildfires that had ripped through Siberia that summer.
Voosen P. 2021. High-flying wildfire smoke poses potential threat to ozone layer. Science 374 I6570, 19 Nov 2021: 2p.