Quote Watsisname (
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So, what are comparable changes through the Holocene, what was the forcing mechanism, and where are they in the climate record?
You argue as what we measure as climate (a thin section of air above the ground) is a function of forcing solely. There also is internal, unforced variability, which can amplify, cancel or reverse the effects of forcing changes.
Quote Watsisname (
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You're sure you don't want to protest the cosmic distance ladder? We stitch together totally different data from totally different methodologies all the time in science.
The issue is comparing something measurable in one methodology with something much less measurable in another methodology. It's not just a matter of calibration when you stitch together things measured differently. Though matching ice cores with global temps probably takes clever calibration, that is not what I point at. A lot more internal variability is visible in the instrument record than in the proxy record. Just because much internal variability doesn't show in the proxy record, it doesn't mean that it didn't exist.
So what is the internal variability in the instrumental record? Since we think we know a lot about forcings and feedbacks, a good guess would be that the internal variability is what the models tell us given the actual forcings minus observations. But you can't then say that this is the variability and it proves that the observations match what we know about the forcings. That's circular.
Quote Watsisname (
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We do not see ~1C global temperature change on century timescales
No wonder, if the proxy has no details shortert than 200 years, like the xkcd graph. Anyway, you can't dismiss such changes without showing that internal variability of that scale is impossible.
One interesting case for this question is the Younger Dryas.
Even if we're confident about the calibration of individual proxies and about the insignificance of internal variability, a proxy for global temperatures is still a leap of faith away. If it wasn't warmer in central Greenland 10 to 6k years ago than today, is it a good proxy when we can be pretty sure that other places were warmer than today? As mentioned before, like the Arctic ocean (fossil beaches at the northern coast of Greenland), or Scandinavia (known from old flora).
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For instance, when the modern warming shows up in the ice core record, we'll know more about how well the record picks up internal variability and we'll also get a firmer calibration. That could take centuries. Meanwhile, we'll learn more about the multidecadal variability. I hope I've been clear that I don't reject the hockey stick because the record can't be like that, but because we don't know that.