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I think this stinks. The Science paper says their reconstruction is smoothed and has low time resolution. They say it preserves no variability at all on timescales <300 years, and attenuates even 1,000 year variations. Superimposing this with the 30-year Hadley data seems misleading, because it is on a very short timescale which is suppressed from the paleologic data.

(edit):

"Because the relatively low resolution and time uncertainty of our data sets should generally suppress higher-frequency temperature variability, an important question is whether the Holocene stack adequately represents centennial- or millennial scale variability. [...] The results suggest that at longer periods, more variability is preserved, with essentially no variability preserved at periods shorter than 300 years, ~50% preserved at 1000-year periods, and nearly all of the variability preserved for periods longer than 2000 years (figs. S17 and S18)."




The realclimate.org post discusses that as a potential issue, yes. See the section following the sentence: Because the proxy data have only a coarse time resolution – would they have shown it if there had been a similarly rapid warming earlier in the Holocene?


I read this as "no, it wouldn't show up".

"Had there been such a global warming before, it would very likely have registered clearly in some of these data series, even if it didn’t show up in the averaged Marcott curve."

I'm not arguing their conclusions. I'm criticizing the way they present this data. This composite reconstruction is so weak, that if you shifted 20th century AGW back 5,000 years, it would completely erase it. That's how powerful the smoothing is.


I can buy that view, yeah. It presents conclusions that are probably true, but the plot is a bit in the pop-science direction in doing so, in the sense that the plot itself is not really a rigorous way of establishing those conclusions. The paper doesn't include this kind of plot, probably for those reasons.




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