Zen 634: New study says that fall of Roman Empire was due to climate change - I say new study is balls

According to a new study of tree growth rings from Roman era wooden artefacts, we can apparently deduce that times of prosperity coincide with wet, warm summers while times of instability and crisis coincide with changes in the climate.

Can you see what they did here? They drew an analogy between the fall of an ancient civilisation that failed to act and was doomed by a shift in the climate, and modern society which is failing to act and is doomed ... etc, blah.

You get the point.

The study, published in the journal Science, looked at 9,000 wooden artefacts from the past two and a half millennia.

"Looking back on 2,500 years, there are examples where climate change impacted human history," asserts co-author Ulf Buntgen, a 'palaeoclimatologist' at the Swiss Federal Research Institute for Forest, Snow and Landscape.

Except that the data doesn't say that at all. That's what Ulf wants it to say, but he's mixing up correlation and causality, a fallacy even the most callow undergrad should have learned to dismiss by the end if week one.

Then there's the sample. Nine thousand items. That's less than four for every year, assuming an even distribution, which we shouldn't. It's unbelievably, microscopically, insignificantly tiny.

Then there's the problematic dating of wooden artefacts, further complicated by the life story of each individual piece, the type of wood employed in its manufacture, the method of manufacture, the provenance of the wood, the local climatic variation (let's not forget that the Roman Empire was very, very big, stretching from Scotland to Syria and the Rhine to the Sahara) and the location and state of preservation when it was found.

And because this was a meta-analysis, you have to account for variations in technique and competence between thousands of individual research groups.

Even then, there's the period the authors determine as 'in crisis', choosing 250 to 600 AD, presumably because that was the best fit for their data. Only, the Third Century crisis began in the mid-230s, thereby presumably discounting climate as a trigger, and from Diocletian onwards the Empire experienced a long period of stability despite the dicky weather.

And in any case, it's a peculiarly one sided, Roman-centric perspective. One man's crisis is another's opportunity, and while the Roman Empire might have been struggling, it's fair to say the Goths, Vandals, etc were making hay.

So apart from the authors' biases, the ludicrously small sample, the basic failure to understand the history of the period and the multiplicity of confounding factors for the dating, it's a really jolly good study.