Greenland. Anecdotal evidence suggests expanding glaciers almost worldwide. Based on radiocarbon dating of roughly 150 samples of dead plant material with roots intact that were collected from beneath ice caps on Baffin Island and Iceland, Miller et al. (2012) state that cold summers and ice growth began abruptly between 1275 and 1300, followed by "a substantial intensification" from 1430 to 1455. In contrast, a climate reconstruction based on glacial length shows no great variation from 1600 to 1850 but a strong retreat thereafter. Therefore, any of several dates ranging over 400 years may indicate the beginning of the Little Ice Age: 1250 for when Atlantic pack ice began to grow, a cold period that was possibly triggered or enhanced by the massive eruption of Samalas volcano in 1257 and the associated volcanic winter. 1275 to 1300 for when the radiocarbon dating of plants shows that they were killed by glaciation 1300 for when warm summers stopped being dependable in Northern Europe 1315 for when rains and the Great Famine of 1315–1317 occurred 1560 to 1630 for when the worldwide glacial expansion, known as the Grindelwald Fluctuation, began 1650 for when the first climatic minimum occurred The Little Ice Age ended in the latter half of the 19th century or in the early 20th century. The 6th report of the IPCC describes the coldest period in the last millennium as: By region Europe The Baltic Sea froze over twice, in 1303 and 1306–1307, and years followed of "unseasonable cold, storms and rains, and a rise in the level of the Caspian Sea.” The Little Ice Age brought colder winters to parts of Europe and North America. Farms and villages in the Swiss Alps were destroyed by encroaching glaciers during the mid-17th century. Canals and rivers in Great Britain and the Netherlands were frequently frozen deeply enough to support ice skating and winter festivals. The first River Thames frost fair was in 1608 and the last in 1814. Changes to the bridges and the addition of the Thames Embankment have affected the river's flow and depth and greatly diminish the possibility of further freezes. In 1658, a Swedish army marched across the Great Belt to Denmark to attack Copenhagen. The winter of 1794–1795 was particularly harsh: the French invasion army under Pichegru marched on the frozen rivers of the Netherlands, and the Dutch fleet was locked in the ice in Den Helder