> We're at historically normal levels of warming.

Misleading. You have to appeal to pre-history to find temperature levels similar to current.

> Eventually we'll plunge into another glacial period, and no amount of CO2 will stop it.

Eventually, i.e. 10's or 100's of thousands of years, if CO2 levels revert to preindustrial.

You are appealing to timescales of thousands of years, but the timescale relevant to the problem and our response is years and decades. Is your comment intended to minimise the problem of current warming? If so why?

The early Holocene does predate the alphabet, but it's only 6,000 years ago, a blink of an eye geologically speaking. There were also several cooling and warming episodes in the interim since then, with the Minoan, Roman, and Medieval Warm periods all exceeding modern temperatures. Historically, warm climate has correlated with boom times for civilization and cold periods have brought famine. See research below:

(Note: CO2 was at least 100 ppm lower than today yet the Arctic hit much higher temps and had to lose much of its ice as a result)

"Peak warmth occurred ~10 ka BP, with temperatures 7 °C warmer than today due to high radiative forcing and intensified inflow of warm Atlantic waters."

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...

Global average temperatures 6000 years ago were 0.5 °C warmer than baseline (1961-1990 average), now it's 1.1 °C. Historical warm periods were local, and global average temps did not exceed current temperatures. (Also, modern is a weasel word here -- you could pick e.g. 1920 and be correct).

Even if warming stopped now, Arctic and Antarctic would continue to melt for decades to come. Rate of change is key.

Your reference is also local (to the arctic), not global.

Again, what argument are you making here?

Is it: 1: It was warmer in the past / 1a: but nothing bad happened / 1b: therefore current warming is not due to human activity / 2: therefore there is no need to reduce CO2 levels.

From the abstract: During peak warmth, summer temperatures were 7 °C warmer than today as more solar radiation and warm water reached the Arctic. However, Early Holocene warming was much slower than today.