You could plant huge new forests where none have been before. You could blast particles into the sky to block the sun's radiation. You could put mirrors in space. These planetary hacks could slow global warming, but one thing that none of them could do, most likely, is to stop the rising sea levels that a warming planet will bring. That's the contention of John Moore, lead author of a study out in the Proceedings of the National Academy of Sciences. Moore's team examined five different means that scientists have proposed to hack the planet and save ourselves from anthropogenic global warming. The geoengineering schemes—forestation, atmospheric aerosols, space mirrors, biochar, and the use of biofuels plus carbon sequestration—are focused either on reducing the amount of energy the Earth absorbs or pulling carbon out of the atmosphere. So Moore wanted to see what they could do about a side effect of the extra heat: melting ice raising the global average sea level. The results weren't terribly encouraging. Sea levels respond slowly to changes in the planet's temperature, Moore told Nature News, so "you can't just slam on the brakes."