"Solar geoengineering" as defined by the IPCC includes any/all forms of solar radiation management (SRM), most notably stratospheric aerosol injection (SAI) and marine cloud brightening (MCB) but also cirrus cloud thinning or orbital mirror deployment (lol).
Notably, this does not include carbon dioxide removal (CDR) technologies such as direct-air capture (DAC), biomass carbon removal and storage (BiCRS), enhanced weathering (EWR), ocean alkalinity enhancement (OAE), or other techniques that simply reduce the concentration of CO2 in the atmosphere. The IPCC definition of solar geoengineering also (somewhat contentiously) does not include surface albedo enhancement (e.g. painting rooftops white).
"Significant scale" here is somewhat arbitrarily defined as having an estimated net decrease in radiative forcing of at least 1 W/m2 for at least one month (about a ~0.4% increase in planetary albedo). This would correspond to a net sulfur injection of about 5 Mt/y for the most commonly discussed SAI technique -- about 0.25 Pinatubos per year.
I will not bet in this market.
1,000
1.00I guess contrail management would count but is unlikely to reach the postulated scale. https://sites.research.google/contrails/
@Thomas42 Correct, I'd argue contrail mitigation is functionally an indirect method of cirrus cloud thinning.