I not sure this is going to resonate much with people about climate change. If you are getting publicity you actually need a message. This will help sell Van Gough prints and super glue, not change the world.
The message has been out there for decades - hell, if not more than a century. We as a species have utterly failed to listen. We're consequently staring down the barrel of an existential threat to humanity's continued survival on Earth. Far more than one Van Gogh painting will be lost, and at this point it's likely too late to do anything about it but triage and mitigate further catastrophe.
No Van Gogh painting will be lost. Those people don't underestand how democracy. They just need a lobbying agency and a revolving door to the government. Glueing yourself to a wall after trying to vandalise a picture does not show anything.
We are 5 past 12 with the climate change but nobody who can make a change, gives a shit.
And no, turning your lights off for 1 hour does not count. It's like trying to cool the Mediteranean sea by trowing an ice cube into it.
I think you're underestimating how difficult it will be to maintain an art gallery / museum amid the increasingly-probable global socioeconomic crisis we're inflicting upon ourselves.
> They just need a lobbying agency
You say that as if ordinary citizens have anywhere near the necessary capital for that.
> nobody who can make a change, gives a shit
Maybe people being sufficiently desperate to resort to vandalism (or, worse, actual violence) would encourage them to give a shit.