You’re wondering how I can know that other people are hallucinating and not me. That’s where it comes in handy to study persuasion and hypnosis. Delusional people leave tells.
One of the tells in this case is an ad hominem attack on whoever disagrees with you on climate science. You can see that happening on my Twitter feed today as the pro-climate-science types are coming after me in numbers. When you see an oversized reaction to what should be nothing but competing scientific claims, that’s usually a tell that someone slipped into cognitive dissonance.