From what I've read, there are many cycles far warmer and just as quickly changing as in the past century. Consensus isn't proof, it's appeal to authority, which is a logical fallacy.

Appeal to authority fallacy occurs when someone asserts a claim solely based on the authority or expertise of an individual or group, without considering the evidence supporting the claim. However, in the case of climate change, the scientific consensus is derived from a robust body of evidence and research conducted by thousands of scientists worldwide

That said, the level of proof is mostly conjecture, contrast and comparison. There are a lot of other mitigating factors at play when we're talking about a solar system. It's not significantly different than what was pushed as the heart-health cholesterol hypothesis as fact for half a century, and was in fact wrong, dramatically wrong.

The level of alarmism doesn't help. According to 2001, Florida should be underwater right now. And that is as we, as a global population haven't dramatically changed much of anything. I'll believe the alarmism, when treaty proposals don't draft out massive exclusions for India, China and African nations.

Do you have an example? Because all of the variations in recorded history, the Medieval Warm Period and Little Ice Age, were less than 0.5C. Also, both were regional and came on over centuries.

Also, the difference between the Ice Age and current interglacial was only 4C. The transition took 6000 years. We are approaching 1.5C and should hit 3C. That is the opposite of Ice Age in a century.

When smart people decide not to accept a given fact no matter the evidence, they become really good at denying it. Instead of accepting the fact, there is always the next "what about ...?"