I think the short answer is, While it is true that the Earth's...

I think the short answer is, While it is true that the Earth's climate has been colder (by many degrees) and sea levels have been both lower and higher in the past (by many meters), those changes happened over much longer timescales (tens or even hundreds of millennia) than the current changes we are seeing today, which are happening rapidly on a scale of decades to centuries. The other factor is that for most of that distant past, Earth was largely bereft of people, not like today's 8 billion many of whom live on the coast i.e. it matters, if one believes at all that people matter.

What is clear is that your and my posts are profoundly OT, I'm surprised a moderator hasn't intervened...