A new paper on proxy reconstructions of temperatures has appeared in Geophysical Research Letters. It involves a reworking of the Esper et. al. numbers for past centuries.
In the abstract (I haven’t looked at the paper yet), it says that the Medieval Warm Period temperature has been adjusted downward by 0.2C. Oops. Maybe MBH wasn’t so far off the mark after all?
Seeing as certain bloggers – or should I say, types of blogger – love looking at revisions of temperature records, you’d have expected someone to pick up on this by now. But no, hang on a minute; this sort of revision is bad news for them. So, silence. I hope some others pick up on this.
Go on, then; here’s that abstract:
Abstract
Proxy records may display fluctuations in climate variability that are artifacts of changing replication and interseries correlation of constituent time-series and also from methodological considerations. These biases obscure the understanding of past climatic variability, including estimation of extremes, differentiation between natural and anthropogenic forcing, and climate model validation. Herein, we evaluate as a case-study, the Esper et al. (2002) extra-tropical millennial-length temperature reconstruction that shows increasing variability back in time. We provide adjustments considering biases at both the site and hemispheric scales. The variance adjusted record shows greatest differences before 1200 when sample replication is quite low. A reduced amplitude of peak warmth during Medieval Times by about 0.4°C (0.2°C) at annual (40-year) timescales slightly re-draws the longer-term evolution of past temperatures. Many other regional and large-scale reconstructions appear to contain variance-related biases.
To me, this sounds like good news.
Old man in a cave 
6 comments
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August 31, 2007 at 9:29 pm
Eli Rabett
Properly put the European Warm Period. . . Thanks for the heads up.
August 31, 2007 at 9:59 pm
fergusbrown
Apparently, Mike thinks it’s no big deal. Perhaps, but it is another nail in the sneptics’ coffin; new work confirms old work you claimed was wrong…
It’s hard top know where to find a welcome if you’re a sneptic these days.
🙂 F.
September 3, 2007 at 6:46 am
John Mashey
it is an interesting result, but probably not very relevant except to a few researchers and general understanding.
Edward Wegman got it right (although denialists never quote this part):
‘As we said in our report, “In a real sense the paleoclimate results of MBH98/99 are essentially irrelevant to the consensus on climate change. The instrumented temperature record clearly indicates an increase in temperature.” We certainly agree that modern global warming is real. We have never disputed this point. We think it is time to put the “hockey stick” controversy behind us and move on.’
Click to access Wegman.pdf
They said it in the report that I studied, and then Wegman said again at the later hearing. This was July 2006. That’s about as clear as it gets.
September 3, 2007 at 10:34 am
fergusbrown
Hi John. It would be so nice if people were rational and able to modify an ill-formed opinion given the opportunity. Fat chance. I still get one or two a week loudly proclaiming ‘The hockey stick is broken! Long live the Auditors!’, as evidence that there is no AGW and that scientists are useless incompetent liars.
For some people, the capacity to ignore facts or reason and persist in perpetuating such folly is inexhaustible.
There’s a lot of context in ‘Wegman’, which not all readers will understand, but suffice it to say that the hockey stick is as well tested a piece of work as there is.
September 4, 2007 at 1:54 am
John Mashey
It would also help if a few more people were statistically numerate, preferably starting in high school. A good course in basic probability and statistics, including especially understanding of error bars, uncertainty, regression trends, and especially detection of gaming … would probably be more useful to most students than a a lot of other things.
September 4, 2007 at 9:29 am
fergusbrown
Unfortunately, there are some otherwise educated people who still belong to the group which either does not or cannot accept that AGW both exists and is a problem. This is something I have been thinking about recently. ClimateDenial is a blog I have mentioned before in this respect, which considers the psychology aspect: I am starting to be a bit more aware of the credibility of some of George Marshall’s arguments.