They've been doing it for decades, and the news reports on it, but then gaslights anyone who talks about stratospheric aerosol injections. Therr have been ongoing tests of these geo-engineering tools for decades.
That's aircraft contrails you're talking about? They're part of standard climate modelling because they behave slightly differently than regular clouds. Or do you mean the sulphur-rich fuels used in shipping until recently, which had a similar impact (though IIRC low level not stratospheric)?
Incidental rather than deliberate geoengineering, but totally monitored and openly discussed.
This is the main unknown with global warming imho: how will it affect the thermoaline circulation. Because if it's 'not much', the adaptation will be hard in some places but possible (and we will be able to predict/modelize risk and mitigate). If it's 'a lot', I'll become religious and pray a lot.
Incidental rather than deliberate geoengineering, but totally monitored and openly discussed.