"By 2050, only stratospheric aerosol injections or sunshades in space have the potential to cool the climate back toward its pre-industrial state," earth scientists Tim Lenton and Naomi Vaughan of East Anglia University in England write.
Many global cooling approaches have been floated. The broad range of the proposals — from injecting the upper atmosphere with sun-blocking particles to creating plankton blooms by feeding them extra iron to burying carbon-filled "biochar" in soil — has made comparing them very difficult. The new study provides the first useful comparisons of a wide variety of geoengineering ideas.
The study did not calculate the costs or environmental impacts of any of the techniques, but for most of the climate hacks, they could be large. For those reasons, the authors of the paper recommend reducing the amount of our emissions, not just banking on geoengineering to bail us out.