We have to commit to metric, every inch of the way.
Anyway, from Wikipedia:
"During the most recent ice age (at its maximum about 20,000 years ago) the world's sea level was about 130 m lower than today, due to the large amount of sea water that had evaporated and been deposited as snow and ice, mostly in the Laurentide Ice Sheet. Most of this had melted by about 10,000 years ago."
Well, because you could die in a horrible natural disaster, why wear your seat belt? There are things that "we" can control the effect "we" are having, and there are things that are totally out of "our" control. So we should just not care about the things we can because things we can't exist is just a very strange leap in logic.
Rather than worry, we need to plan for the devastation caused to the people and massive investments in infrastructure that lie within centimeters of the current sea level.
The problem with inferring ancient temperature is you have to rely on sparse proximal data (ie tree rings, ice cores, etc) that is only accurate within 1 or 2 degrees C for estimation and then you have to fill in whatever's missing, geographically and temporally.
Still sometimes the data does indicate sharp, dramatic changes, such as the Younger Dryas, about 12K years ago. After the recent glacial period ended, roughly 14K YA, there was a plunge back to glacial temps over a couple centuries which lasted about 1200 years, then very suddenly the temperature rose almost 20C.
The issue with doubting ancient temperatures, is that one has no faith in the predictions of science for the present, as this is the basis/metric in use.
Putting aside the arguments on the merits of global warming ideology, your logical argument doesnt make sense, the sea rise in question was on the back of an ice age that receeded the waters prior, just because things have multiple causes doesnt mean it invalidates the other.
Also, there is serious evidence that this one is anthropocenic.
And finally, even if it wasn’t, our societies will be affected so much that it is a good investment to work on preventing it.
And finally - Earth had it’s periods when it had o2 contents so low that humans wouldn’t survive, ditto with co2 levels being so high at times that we would feel like in an extremely stuffy room at all times.
In the Baltic, it did happen rapidly, and the lake level variously fell and rose as glaciers melted and flowed and moraines dammed the narrow strait that separates it from the North Sea.
From 14,000 years ago to 6,500 years ago (pre-human), the sea level rose 110 meters. That's 14mm/yr.
From 1880-now (industrial era), the sea level rose ~0.2 meters. Thats 1.4mm/year, an order of magnitude less.
From 2006-2014 ("things are really bad!" era), the sea level rose 3.6mm/yr. About a quarter of how quickly they rose before there was any human intervention at all, yet people will still insist that this rise is due to human behavior.
Ancient sea level rise was so catastrophic to human proto-civilization that to this day the most common cross-cultural ancient mythological remnant is the flood myth: https://en.wikipedia.org/wiki/Flood_myth . A sea level rise of even a fraction of that would be similarly catastrophic.
Meanwhile, your argument is a non sequitur. Arguing that the sea level has previously risen faster without human intervention provides absolutely no argument against the fact that modern sea level rise is a result of human activity. We have evidence that the temperature is rising faster now than it has in the past 20,000 years (https://xkcd.com/1732/), curiously coinciding with the advent of the industrial revolution, and we understand well the mechanisms that have caused it and are still causing it.
You're afraid of change. That's understandable. I empathize. Hiding from the truth won't help.
(also note from this data, that the earth was warmer in the first half of the Holocene, we have been trending lower despite the recent mild increases)
Secondly, no we do not have evidence that it's rising faster than any time in the past 20K years. The end of Younger Dryas was a 20C increase in less than a couple hundred centuries.
