The best messaging I've seen (IMO) is this ELI5:
“blanket of pollution trapping heat on Earth”. Every oil and gas emission makes that blanket thicker – and all that trapped heat helps cause floods and start fires
I think it's helpful that it doesn't mention the obvious anxiety words that will cause people to tune out, and makes a very simple & direct connection between burning it and the impacts of climate change.
From here
There's a quote from Greta Thunberg which from memory goes roughly: