Earlier quoted context omitted.
So would you say the claims are unfounded? I don't think it all hinges on tree rings, they are just one indicator of many.
I'm not sure which claims you mean. The specific claim that it's significantly warmer now than it was about a thousand years ago during the MWP does mainly hinge on (a) tree rings, (b) ignoring the difference between high frequency and low-frequency information sources, (c) ignoring the error bars. We can't say with any certainty that current temperatures are "unprecedented" compared to the last big peak and it seems…
I must admit to me it sounds a bit like the typical creationist argument: "but you can't explain how bone X came into existence". So never mind that evolution theory doesn't even claim to be able to provide a causal evolutionary path for every animal, and that it has been validated in countless examples (more than any other theory afaik), they find a single example that is not even relevant and use it as an excuse to dismiss the whole theory.
I don't call you a creationist, I just want to warn that you might be victim to the same kind of fallacy.