The issue is that scientists aren't quite sure how much good that would do or whether geoengineering might inadvertently trigger new problems.

The European Commission says the world needs to start thinking about rules on geoengineering. Without them, climate vigilantes could decide to go ahead with their experiments without any oversight or accountability. This is starting happen on a small scale. 

One of the problems that the EU has is that conspiracy theorists think it is already using atmosphere-altering chemicals itself.