Investment firms have put over $100 million into developing risky technologies that could cool the planet with unknown side effects.

Should private companies be able to dim the sun? Solar geoengineering aims to manipulate the climate by bouncing sunlight back into space. In theory, it could ease global warming. But as interest in ...

For years, the idea of geoengineering—artificially lowering global temperatures through technological means—has been met with skepticism. Only a handful of dedicated and much-criticized scientists ...