[ben_w]

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.

[zosima]

The global sulphur dioxide emission has gone down continuously since the 80s [1], and ship emissions are a small fraction of the total emissions.

The recent spike in temperatures is obviously related to an el Nino. It will go down again, just like it's done after every other el Nino.

[1] https://ourworldindata.org/grapher/so-emissions-by-world-reg...

[orwin]

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.

[Izkata]

I think they're referring to cloud seeding, which has been a thing for decades. Just not exactly what the topic is about.