The Little Ice Age cooled regions, not the whole planet in lockstep
Named by François E. Matthes in 1939, the Little Ice Age was regional cooling—especially around the North Atlantic—not a true global ice age. Conventional dating runs from the sixteenth to nineteenth centuries; some specialists prefer roughly 1300 to 1850.
NASA notes cold spells centered near 1650, 1770, and 1850, each separated by milder stretches. The IPCC's Third Assessment Report stressed that glacier advances in Alaska, New Zealand, and Patagonia were not synchronized, and that Northern Hemisphere cooling was modest—under one degree Celsius next to late-1900s benchmarks. A later IPCC framing describes a multicentennial cool stretch beginning around the fifteenth century, with global mean surface temperature about –0.03°C (range –0.30 to 0.06) between 1450 and 1850 versus 1850–1900. Northern Hemisphere onset is placed between 1200 and 1400; the Southern Hemisphere lagged by roughly two centuries.
Proposed drivers include solar lows, volcanoes, ocean circulation shifts, orbital forcing, natural climate variability, and population crashes after events such as the Black Death or epidemics in the Americas. Candidate start markers include Atlantic pack ice growth around 1250 (possibly tied to the 1257 Samalas eruption), plant-killing ice advance between 1275 and 1300, unreliable warm summers in Northern Europe after 1300, the Great Famine rains of 1315–1317, and the Grindelwald Fluctuation of worldwide glacial expansion from about 1560 to 1630. Central European winter reconstructions show seventeenth- and nineteenth-century winters about 1.2°C below the 1961–1990 mean.
Lived effects were vivid. Swiss Alpine farms were destroyed by mid-seventeenth-century glaciers; British and Dutch canals froze hard enough for skating festivals, with Thames frost fairs from 1608 to 1814. In early 1658 a Swedish army marched across Denmark's Great Belt on ice to strike Copenhagen. Icelandic harbors closed under miles of sea ice; population there fell by half, though skeletal fluorosis after the 1783 Laki eruption may explain much of that loss. Cod vanished from Faroe waters after late-seventeenth-century cooling, which Hubert Lamb linked to southward Arctic water.
Source: Little Ice Age
