Little Ice Age

The thirteenth-century cooling that has no date

Retreating Arctic ice has exposed rooted moss that died when advancing ice buried it roughly eight centuries ago — the closest thing this transition has to an event.

Nothing happened worldwide in 1250

1250 is a rounded label, not a switch. Continental-scale reconstructions by the PAGES 2k Consortium find no globally synchronous Medieval Warm Period or Little Ice Age, and Neukom and colleagues found no globally coherent warm and cold periods across the preindustrial Common Era.

The Intergovernmental Panel on Climate Change avoids leaning on either term precisely because their timing is poorly defined and varies by region.

What can be dated is regional: around the middle of the thirteenth century, expanding ice caps in Arctic Canada overran and preserved rooted tundra vegetation.

Onset dates that do not agree

A recent compilation of Arctic Canadian moss kill dates has an early ice-expansion peak near 1240. The 2012 Arctic study behind much of this line of evidence radiocarbon-dated roughly 150 rooted plant samples.

A separate study using Arctic Canadian and Icelandic evidence placed an abrupt regional onset of cold summers and ice growth between 1275 and 1300, followed by intensification in 1430–1455.

The regional order differs too: PAGES 2k found the transition arriving earlier in the Arctic, Europe and Asia than in North America and the Southern Hemisphere, and a 2019 global analysis found different regions reaching their coldest epoch in the fifteenth, seventeenth or nineteenth centuries.

The volcano arrives seven years late

Samalas erupted on Lombok in 1257, seven years after the listed date, and may have contributed to subsequent cooling. It cannot itself be an event that occurred in 1250.

No single global trigger has been settled. Long-term orbital forcing, internal ocean–atmosphere variability and clusters of volcanic eruptions are among the mechanisms studied for regional cooling.

Frost fairs, famines and glacier maxima are later and regional, and cannot be treated as immediate consequences of the year 1250.

Sources

Researched 23 Aug 2026 7 sources 2 audit passes Date disputed

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Date disputed. Sources disagree; the research places it at ~1250.

What the sources leave uncertain

The prefix “~” is essential: 1250 is an approximate convention, not a dated global event.
Different studies define the Medieval Climate Anomaly and Little Ice Age differently. The IPCC notes that their timing is not well defined and varies regionally.
Arctic Canadian moss kill dates near 1240 support a regional mid-thirteenth-century ice expansion, while another influential study dates abrupt Arctic Canada/Iceland cooling to 1275–1300.
A 2019 global analysis found that different regions experienced their coldest epoch in the fifteenth, seventeenth or nineteenth centuries, further undermining a single worldwide transition date.