Geoengineering is a risky way to blunt the effects of climate change. But climate scientist David Keith says we still need to consider it seriously.
Humanity can burn less than one-sixth of its known fossil-fuel reserves. That's one upshot of the big new IPCC report.
A California businessman has been seeding the Pacific Ocean with iron in order to trigger plankton blooms. It's a promising scheme to help cool the planet. But there's a catch: he appears to be doing it on his own, possibly illicitly. This raises the unnerving possibility of "rogue geoengineering."