A new study shows modern temperatures are not unprecedented and disproves an important part of Mann’s “hockey stick” paper of 1999.
Orbital forcing of tree-ring data, J. Esper et al., says:
“… large-scale near-surface air-temperature reconstructions [specifically the hockey stick] relying on tree-ring data may underestimate pre-instrumental temperatures including warmth during Medieval and Roman times.”
This is beautiful.
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I see HT seems to be silent on that one. Still embracing Mann 🙂
Of course there’s been numerous studies over the years that have said the same. Inconveniently get’s in the way though.
Actually it’s still a hockey stick of sorts – just more like a stubby field hockey stick with a couple of thick offset hand grip wrappings than it is an ice hockey stick.
Very unwieldy I would have thought being an ex field hockey player from school days.
Mann’s “hockey stick” was a meta-study (a study of studies) and this is only one data-set from one part of the globe.These are boreal forests, which shut down over winter so there would be no information on winter temperatures. It would be interesting to know what is affecting tree growth over the most recent decades.
Simon, my understanding is that MBH wasn’t a meta-study, it was a flawed technique using many proxies. The flaw was two fold: the baseline averaging, followed by the selection method that weighted massively in favour of hockey-stick shaped proxies. Indeed, it was proven later that even random red noise-generated data sets would produce a hockey stick shape.
The winter temperatures shouldn’t matter, as long as we compare like with like. Ie: the tree growth 2,000 years ago was higher than in recent years. Unless someone can show that these trees grew in a different way 2,000 years ago, the result is valid.
The paper is interesting in that it’s a high-quality series, made up of 587 data series. It may be from only one region, but it exhibits all the characteristics of the known historical and archeological records: a RWP followed by a cool Dark Ages, then the MWP, LIA, and CWP. The RWP is warmer than the MWP which was marginally warmer than the CWP. So it confirms what is already known from countless other global sources.
The outlier is MBH, and it has been proven to be fatally flawed, which explains why it’s the outlier.