[aurelwu]

iron seeding can increase amount of cyanobacteria which recently have been identified as potentially being methanogenic, thus this might not be a good idea. Unintended side effects of most geoengineering solutions are a big problem - some things like marine cloud brightening might be a bit less risky though. The other big issue is that most of those measures are just a bandaid which offsets a fixed amount of CO2, so it counter acts a few years of emissions but then you can't scale it up anymore. Adding Sulfur to the atmosphere for example can have a cooling effect but alongside other bad effects like acid rain, there are also studies showing that after a certain amount of sulfur, it does not provide a lot of negative forcing anymore.