This is today’s edition of The Download, our weekday newsletter that provides a daily dose of what’s going on in the world of technology. Hacking the atmosphere: geoengineering gets a reality check Solar geoengineering, the controversial idea that we could deliberately intervene in the climate system to counteract global warming, is moving beyond computer simulations…

Jim Franke pulls away the cover page of a presentation on the wraparound desk in his office, revealing an illustration of an odd-­looking aircraft with massive wings stretching out from a stubby fuselage. The uncrewed plane is soaring thousands of meters higher than commercial jets fly—so high you can see the curvature of the Earth.…