Warming from the end of the Little Ice Age.

The Little Ice Age (LIA) was a period of cooling that occurred after the Medieval Warm Period (Medieval Climate Optimum).[1] While it was not a true ice age, the term was introduced into the scientific literature by François E. Matthes in 1939.[2] It may be conventionally defined as a period extending from the 16th to the 19th centuries,[3][4][5] or about 1350 to about 1850[6] though climatologists and historians working with local records no longer expect to agree on either the start or end dates of this period, which varied according to local conditions. NASA defines the term as a cold period between 1550 AD and 1850 AD and notes three particularly cold intervals: one beginning about 1650, another about 1770, and the last in 1850, each separated by intervals of slight warming.[7] The Intergovernmental Panel on Climate Change (IPCC) describes areas affected by the LIA:


Evidence from mountain glaciers does suggest increased glaciation in a number of widely spread regions outside Europe prior to the 20th 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 time frame, 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 20th century levels.[8]

Several causes have been proposed: cyclical lows in solar radiation, heightened volcanic activity, changes in the ocean circulation, an inherent variability in global climate, or decreases in the human population. Lower CO2 atmospheric concentrations found in Antarctic ice cores may have resulted from the colder global climate.


On the MWP or a hot time for all.


The idea of a medieval warm period was formulated for the first time in 1965 by the English climatologist Hubert H. Lamb [1]. Lamb, who founded the UK Climate Research Unit (CRU) in 1971, saw the peak of the warming period from 1000 to 1300, i.e. in the High Middle Ages. He estimated that temperatures then were 1-2 ° C above the normal period of 1931-1960. In the high North, it was even up to 4 degrees warmer. The regular voyages of the Vikings between Iceland and Greenland were rarely hindered by ice, and many burial places of the Vikings in Greenland still lie in the permafrost.

Glaciers were smaller than today

Also the global retreat of glaciers that occurred in the period between about 900 to 1300 [2] speaks for the existence of the Medieval Warm Period. An interesting detail is that many glaciers pulling back since 1850 reveal plant remnants from the Middle Ages, which is a clear proof that the extent of the glaciers at that time was lower than today [3].

Furthermore, historical traditions show evidence of unusual warmth at this time. Years around 1180 brought the warmest winter decade ever known. In January 1186/87, the trees were in bloom near Strasbourg. And even earlier you come across a longer heat phase, roughly between 1021 and 1040. The summer of 1130 was so dry that you could wade through the river Rhine. In 1135, the Danube flow was so low that people could cross it on foot. This fact has been exploited to create foundation stones for the bridge in Regensburg this year [4].

Clear evidence of the warm phase of the Middle Ages can also be found in the limits of crop cultivation. The treeline in the Alps climbed to 2000 meters, higher than current levels are [5]. Winery was possible in Germany at the Rhine and Mosel up to 200 meters above the present limits, in Pomerania, East Prussia, England and southern Scotland, and in southern Norway, therefore, much farther north than is the case today [6]. On the basis of pollen record there is evidence that during the Middle Ages, right up to Trondheim in Norway, wheat was grown and until nearly the 70th parallel/latitude barley was cultivated[4]. In many parts of the UK arable land reached heights that were never reached again later.

Also in Asia historical sources report that the margin of cultivation of citrus fruits was never as far north as in the 13th century. Accordingly, it must have been warmer at the time about 1 ° C than today [7].