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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:


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.

I have tried to post this comment on Stoat, in reply to this post, but the server is playing up and not letting me through. I’ll try again later. In the meantime, here is one possible line of argument:

No, it’s okay; it’s now on there three times. Sorry, William.

Does scientific opinion on climate change matter, beyond the PR value? Of course it does. Not so much within science itself, perhaps, though there are those who would argue this too, as it might help liberate the ‘voices’ of individuals who could be intimidated by the prospect of opprobrium and thus prevented from voicing their true opinion.

Where the value in understanding scientific opinion lies mostly is in the critically important interface between scientific results and public attitudes. If the survey of public responses to CC cited today on the radio is correct, 90% of the public are aware that they should be doing something about climate change, but only 10% actually do it. At least one plausible explanation for why people aren’t changing their habits (and this applies to governments, too) is that there is no clearly established and trusted ‘authority’ to act as a guide. It is a given that a rational person would want reason to be the guide, and in CC, this means climate scientists. Whether the expectation of a definitive, clear message is misplaced or not doesn’t bear: the public perception is that the science is still ‘uncertain’ (a loaded, multi-meaning term).

If the public or policy makers are in a position to see that climate scientists can speak with ‘one voice’, even on a relatively straightforward matter, this offers a reassurance and a motive for ending apathy. Perhaps this shouldn’t be how things work, but it is (at least in part), how it seems to pan out in the real world. In brief: we want to be told, without prevarication, ‘the truth’.

As to how you establish what that opinion is: there is a lot of value in reviewing the findings of a collection of papers (and the embedded research) on a regular basis, and keeping the public up-to-date with the ever-progressing understanding of what is going on and how the body of evidence is developing. OTOH, if you want to know what someone thinks, surely the easiest way is to ask them.

Polls and reviews alike need careful construction and considerable thought for any meaningful and valid conclusions to come from them. They also need to be robust to criticism and open to discussion and revision. This may be a difficult task, but it is not beyond the competence of a dedicated team of researchers to achieve.

For the benefit of scientists and the public alike, I suggest then that having a clear notion of what scientists think is one of a number of desirable, if not necessary ways of getting the message across in a way which will improve the prospects of CC action being timely and potent.



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August 2007