Dating the Past

Historiscientific nerd alert: There's a hot new method of dating historical artifacts, specifically ceramic artifacts, based on their moisture uptake. But there's at least one big problem -- it assumes that mean temperatures are constant. HNN's Jonathan Jarrett has the goods, in a paragraph so well-linked that I've cut-and-pasted them all. (I also changed some of the punctuation and split Jarrett's long paragraph into a few short ones.)

Now, you may have heard mention of a thing called "the medieval warm period." This is a historical amelioration of temperature in Europe between, roughly, the tenth and twelfth centuries. This probably decreased rainfall and other sorts of weather bad for crops, therefore boosted agricultural yield, pumped more surplus into the economy, fuelled demographic growth and arguably deliquesced most European societies to the point where they changed in considerable degree.

However, because of the current debate on climate change, it has become a ball to kick around for climate "scientists," those who wish to argue that we're not changing the climate pointing to it and ice coverage in Norse-period Greenland (which was less than there is currently despite less carbon dioxide in the atmosphere then), while those who wish to argue that we are changing the climate (and, almost always, that this relates to CO2 output, which does seem like a weak link in the argument) dismiss it as legend or scorn the very few and unscientific datapoints, not really caring that the historical development of European society in the ninth to eleventh centuries just doesn't make sense without this system change from the ground. None of these people are medievalists and they're not trying to prove anything about the Middle Ages, so it gets messy, but there is a case about this temperature change that has to be dealt with.

This obviously has an impact on this research. If the sample were old enough, the errors and change probably ought to balance out. But if it were, from, say, the eighth century, then the moisture uptake in the four or five subsequent centuries would be higher than expected from the constant that this research used and the figure would be out, by, well, how much? The team didn't know: "The choice of mean lifetime temperature provides the main other source of uncertainty, but we are unable to quantify the uncertainty in this temperature at present."

We, however, need to know how far that could knock out the figures. Twenty years? More? It begins to push the potential error from a single sample to something closer to a century than a year. That is, the margin of historical error (as opposed to mathematical error) on this method could be worse than that of carbon-dating, and we don't actually know what it is.

Lots of good stuff in the whole, long post, including an annotated run-down of ALL of the ways we know how to date old things.