Glacial Biome

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Lore & Background

The Intergovernmental Panel on Climate Change Third Assessment Report (TAR) of 2001 described the areas that were affected: evidence from mountain glaciers does suggest increased glaciation in a number of widely spread regions outside Europe prior to the twentieth century, including Alaska, New Zealand and Patagonia. However, the timing of maximum glacial advances in these regions differs considerably, suggesting that they may represent largely independent regional climate changes, not a globally-synchronous increased glaciation. Thus current evidence does not support globally synchronous periods of anomalous cold or warmth over this interval, and the conventional terms of "Little Ice Age" and "Medieval Warm Period" appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries. [Viewed] hemispherically, the "Little Ice Age" can only be considered as a modest cooling of the Northern Hemisphere during this period of less than 1°C relative to late twentieth century levels. The IPCC Fourth Assessment Report (AR4) of 2007 discusses more recent research and gives particular attention to the Medieval Warm Period: when viewed together, the currently available reconstructions indicate generally greater variability in centennial time scale trends over the last 1 kyr than was apparent in the TAR. The result is a picture of relatively cool conditions in the seventeenth and early nineteenth centuries and warmth in the eleventh and early fifteenth centuries, but the warmest conditions are apparent in the twentieth century. Given that the confidence levels surrounding all of the reconstructions are wide, virtually all reconstructions are effectively encompassed within the uncertainty previously indicated in the TAR. The major differences between the various proxy reconstructions relate to the magnitude of past cool excursions, principally during the twelfth to fourteenth, seventeenth and nineteenth centuries.

In Their Own Story

There is no consensus on when the Little Ice Age began, but a series of events before the known climatic minima have often been referenced. According to J. M. Lamb of Cambridge University, the Little Ice Age was already underway in Canada and Switzerland and in the wider North Atlantic region in the 13th and the 14th centuries. In the 13th century, pack ice began advancing southwards in the North Atlantic, as did glaciers in 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 the length of glaciers 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 the 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, not the start of the Little Ice Age, but the start of the coldest years midway through, i.e., the First Climatic Minimum. 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: a multi-centennial period of relatively low temperature beginning around the 15th century, with GMST averaging –0.03 [–0.30 to 0.06] °C between 1450 and 1850 relative to 1850–1900. The definitions for the beginning and end of the LIA differ considerably, depending on the region and dataset used. The LIA in the Northern Hemisphere started between 1200 and 1400 AD. In the Southern Hemisphere the beginning of the LIA was delayed by about two centuries.

Reader's Guide

In 2021, historian Christian Pfister and climatologist Heinz Wanner published a reconstruction of seasonal temperatures in Central Europe using temperature indices (historical climatology) based on documentary data. After CE 1500, the reconstruction is based on an article by Czech geographer Petr Dobrovolny, which includes monthly, seasonal and annual temperature estimates for Germany, Switzerland and the Czech lands based on temperature indices up to 1759 and subsequent temperature measurements. Winters from 1000 to 1999 were generally cold until the end of the 19th century. A reconstruction of winter temperatures on a year-by-year basis from 1170 onward reveals a different picture of the Little Ice Age. The 13th-century winters were predominantly cold only in the first third of the century, as well as between 1270 and 1280. During the 14th century, cold winters were the norm, except for the 37 years between 1340 and 1377. The 15th century was almost entirely cold, except for the 1470s. Until 1520, winters remained mostly cold. During the 16th century, cold and warm seasons were balanced until 1540. After that, cold winters became the norm, with particularly severe winters occurring between 1565 and 1573 and again from 1587 to 1595. Overall, winter seasons were around 0.9 °C (±0.69 °C) below the 1961–1990 average. During the 17th century, temperatures were 1.2°C (±0.69°C) below average. During the 18th century, temperatures were 0.9°C (±0.69°C) below average. During the 19th century, temperatures were 1.2°C below average based on thermometric measurements. The 20th-century temperatures were 0.2°C below the 1961–1990 average, with positive values dominating after 1950. Conclusion: The duration and intensity of cold spells in winter have increased since the 14th century, peaking in the 15th, 17th, and 19th centuries. The gradual decline in winter temperatures until the early 20th century, compared to the 1961–1990 measurement period, was one manifestation of the end of the Little Ice Age in Central Europe due to Global Warming. 14th-century summers were slightly cooler than warm ones in the 14th century. The years from 1324 to 1340 and from 1380 to 1399 were predominantly warm, whereas the years from 1314 to 1322 and from 1355 to 1370 were mostly cold. The latter cold period triggered an advance of the Alpine glaciers, reaching its peak in the 1380s. Cold summers predominated in the 15th century. After a relatively warm period until 1424, the trend reversed. Seven cold summers occurred in the 1450s alone, presumably in connection with the eruption of a tropical volcano (Kuwae). Also notable is the sequence of three hot summers between 1471 and 1473. During the 16th century, estimated temperatures were 0.2 °C (±0.49 °C) below the 1961–1990 average. Due to ten hot and dry summers, temperatures from 1534 to 1567 were 0.3 °C (±0.49 °C) above average, causing the glaciers to melt back somewhat. Subsequently, temperatures fell in conjunction with high summer precipitation, reaching a low point in the 1590s and triggering the widespread advance of Alpine glaciers. During the 17th century, estimated temperatures were 0.2°C (±0.49°C) lower than the average for the period 1961–1990. Until around 1630 and from 1670 to 1685, extremes of cold and warmth dominated, with warm summers occurring mid-century. After 1675, temperatures fell by an average of 0.6 °C until the turn of the century. Cod, which is sensitive to cold temperatures, disappeared from the waters around the Faroe Islands. The English climatologist and historian Hubert Lamb concluded that cold Arctic water had spread southwards. Warm summers prevailed during the 18th century, particularly between 1718 and 1731. Temperatures remained relatively low between 1760 and 1779, triggering an advance of the Alpine glaciers. Cold summers prevailed during the 19th century. Average temperatures in Central Europe were 0.6 °C below the 1961–1990 average. The first half of the century was predominantly cold, leading to glacier advances. In the 20th century, summers in Central Europe remained cold until 1927. Temperatures then rose until the w

Did You Know?

• The term 'Little Ice Age' was introduced into scientific literature by François E. Matthes in 1939.
• The NASA Earth Observatory notes three particularly cold intervals: one began about 1650, another about 1770, and the last in 1850.
• Based on radiocarbon dating of roughly 150 samples of dead plant material with roots intact, Miller et al. (2012) state that cold summers and ice growth began abruptly between 1275 and 1300.
• The massive eruption of the Samalas volcano in 1257 may have triggered or enhanced a cold period when Atlantic pack ice began to grow.
• The 6th report of the IPCC describes the coldest period in the last millennium as averaging –0.03 °C between 1450 and 1850 relative to 1850–1900.