If I was a billionaire I'd be spending money to ensure planet Earth is habitable.
Climate change prevention is a meme for rich countries. It's an unwinnable battle.
I'm not saying we shouldn't be paying attention. We absolutely should. But humans follow gradient ascent and won't be willing to handicap every area of life to make modest gains on the climate front.
Paper straws don't even make a dent.
It's happening, and we'll just have to adapt. Sucks immeasurably for the current biodiversity, but life has adapted to much warmer climate in the past. We should catalog what we can while we can.
To address your comment, I think you'll find greater success in extending the lives of rich and powerful people. Once they realize there's a long term ahead, they'll adjust their thinking and time horizons.
It seems potentially worthwhile to fight a figurative battle for stemming climate change in order to try and reduce the risk of setting off a chain of events that could lead to a literal war.
That said, I suspect that fretting about space tourism also wouldn't make much of a dent. Maybe more than worrying about straws, but I bet we would get a lot more out of, e.g., allowing the real price of meat to rise back up to what it was 50 years ago.