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....

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...