Climate change increasingly affecting people denying climate change makes it more likely they will one day accept it. I don't know how true that is, but that's my view on this particular line of thought.
Karma is believed to work across lifetimes. Without it we'd not be free to make mistakes. So is more about reincarnation, and not about revenge, justice systems or retribution. Misguided belief in karma may wither away at sense of necessary fairness (dharma), which is also karma.
I feel like that’s a normal human thing to say. People usually say it’s sad when people are affected by bad things, and don’t put a great deal of thought into every implication of how they phrase things. I don’t know, maybe you’re more a fan of karmic justice than of sad irony.