It seems obvious. Just tell the facts!
You may have great social circles with intelligent and curious people, but in my life the facts don’t work because the facts don’t matter. The number of people actually interested in the science and not just the science (tm) is dismally low, we’re talking less than 10% in my experience. This includes people who have degrees in physics and engineering and a university engineering professor I knew.
People are hungry, vulnerable, emotional, scared, and prideful creatures. That’s what we are; and we like stories. We like stories where we’re hero’s on an epic journey with villains to defeat.
If you tell someone a fact that breaks their story, makes them scared, and makes them less prideful, you’re not having a conversation for very long, doesn’t matter if you can support it with evidence and reasoning. What PR added on top of this human tendency is people think about climate way more than they otherwise would, they think about it in terms of a story, in us vs. them terms (PRs narrative), and if you say something counter to that narrative, now you’re the villain.
I’ve had people I respect flat out tell me that climate change is a hoax and if we reduced carbon emissions it would just be virtue signaling. They are not joking, they are serious and they’ve been told this by talking heads for over 20 years.
You’ll never get to the back of the envelope calculation.