This story is at various places and in various newspapers, such as The Guardian and at http://archaeologynewsnetwork.blogspot.co.uk/2012/08/mass-grave-in-londo... ... but has an ultimate origin in an article in the latest issue of Current Archaeology 270 (Aug/Sept 2012) (www.archaeology.co.uk). A mass burial pit in East London with thousands of medieval skeletons was at first thought to be as a result of the Black Death, in the 14th century, or even perhaps the Great Famine of 1315-17. Now, it is being suggested, as a result of C14 methodology, they were caused by an earlier famine event associated with a giant volcanic explosion - in 1258AD. Now, the culprit is as yet unknown but the finger is being pointed at the usual suspects, volcanoes in Indonesia and South America - see also www.archaeology.co.uk/articles/features/londons-volcanic-winter.htm?ht
Meanwhile, at http://phys.org/print263459917.html ... it has been found that glaciers in Switzerland expanded during a cold spell dated between 3800 and 3200 years ago. This coincides with the Bronze Age which was otherwise a relatively prosperous period in most places in the world - so what do the glaciers reflect? Glaciation is not an exact science -especially when they contract and expand over time. The researchers were actually dating rocks they believed were frozen at a particular time in the past so there is a margin of error. Might it also reflect an anomaly in C14 methodology, particularly when the Bayesian method is used. Or did the glaciers expand as a result of cooling 4000 years ago, or earlier? - taking a certain amount of time to manifest itself in actual glaciation. Unlikely. The Little Ice Age glaciation was quite quick. Something seems to be wrong in this study published in the journal Geology.
Finally, at http://phys.org/print263471703.html ... Snowball Earth was not quite the snowball imagined -there were interglacials. Either that or the Earth, 715 million years ago, was bouncing around like a ping pong ball. Now, the idea of Snowball Earth comes from evidence of glaciation in the tropics. If there was evidence of glaciation at the equator and then the Earth must have been very cold. For example, in northern Namibia, ice debris was laid down but was apparently followed by a l ayer of non-glaciated shale, a formation that divides or is sandwiched between a topping and a bottom of glaciated material. Why? Movement at the Poles - out of the question. Junk science. Uniformitarianism will not countenance such an outlandish idea.