Sorry, I don't think ice cores can tell what were the temperatures. I don't think they even tell years correctly. But, would be nice to see how they prove their opinion correct.
Yes, it is nice to learn and understand, but that's only available to those who pursue knowledge. You've been batting if off.
This has been a discussion about climate, and you're playing the
convince me though I'm impossible to convince game. I know that you're a creationist from previous encounters, but creationists don't usually get involved in this dispute. It's usually over biology, not climate science. I wonder what religious belief you're defending? Is the objection that the earth could be 20,000 years old?
What do you suppose is in for you to play that game? If you think it makes you look curious, it does the opposite. It demonstrates your incuriosity when you reject the help offered you out of hand. If you think it implies that evidence and reason are your path to belief, same answer. It underscores your aversion to these things.
You'll notice that when I addressed this earlier with you - when I said that these answers aren't for you to know without effort and open-mindedness on your part - that I also didn't try to tell you that you were wrong or go find you a link or citation - because the outcome after doing that was a foregone conclusion, and we saw it play out. Others tried to help you, but you refused it.
And you'll notice that I haven't disagreed with your scientific misstatements above, because I understand the futility of that and don't care to play Charlie Brown to your Lucy with the football.
So, enjoy your creationist worldview, deny climate science if you feel you need to maintain your faith, or whatever it is that's going on here, because there is no other path for you without a course correction, and you have no interest in that.