“For the scientists of GISP-2, year-to-year levels of gases and aerosols were measurable in the ice, either as solutes in the water itself or trapped as gas bubbles in each layer of core. The resolution was clear enough to identify fallout from postwar nuclear tests and the Chernobyl reactor accident in 1986. It was a heroically tedious task, much of it conducted on scene by people clad in freezer suits and polar gear to fight hypothermia. The reward was a timeline of atmospheric data more than a thousand centuries long, with a previously unseen level of detail.”