Signs of the times.

Harvard scientists plan to launch a balloon this summer to test the equipment needed for the first geoengineering experiments in the stratosphere. by James Temple archive page February 19, 2021 Trapped inside a long glass tube in a ground-floor lab at Harvard University is a miniature copy of the stratosphere. When I visited Frank Keutsch in the fall of 2019, he walked me down to the lab, where the tube, wrapped in gray insulation, ran the length of a bench in the back corner. By filling it with the right combination of gases, at particular temperatures and pressures, Keutsch and his colleagues had simulated the conditions some 20 kilometers above Earth’s surface. In testing how various chemicals react in this rarefied air, the team hoped to conduct a crude test of a controversial scheme known as solar geoengineering, which aims to counter climate change by spraying tiny particles into the stratosphere to reflect more of the sun’s heat back into space. But is what’s in that tube ...