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. ![]() Dating The last written records of the Norse Greenlanders are from a 1408 marriage at Hvalsey Church, which is now the best-preserved Norse ruin. 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. 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 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. 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 IPCC Fourth Assessment Report (AR4) of 2007 discusses more recent research and gives particular attention to the Medieval Warm Period: hemispherically, the "Little Ice Age" can only be considered as a modest cooling of the Northern Hemisphere during this period of less than 1☌ relative to late twentieth century levels. 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. 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. The Intergovernmental Panel on Climate Change Third Assessment Report (TAR) of 2001 described the areas that were affected:Įvidence 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. Several causes have been proposed: cyclical lows in solar radiation, heightened volcanic activity, changes in the ocean circulation, variations in Earth's orbit and axial tilt ( orbital forcing), inherent variability in global climate, and decreases in the human population (such as from the massacres by Genghis Khan, Black Death and the epidemics emerging in the Americas upon European contact ). At most, there was modest cooling of the Northern Hemisphere during the period. ![]() The Intergovernmental Panel on Climate Change Third Assessment Report considered that the timing and the areas affected by the LIA suggested largely independent regional climate changes, rather than a globally synchronous increased glaciation. One began about 1650, another about 1770, and the last in 1850, all of which were separated by intervals of slight warming. The NASA Earth Observatory notes three particularly cold intervals. The period has been conventionally defined as extending from the 16th to the 19th centuries, but some experts prefer an alternative timespan from about 1300 to about 1850. ![]() ![]() The term was introduced into scientific literature by François E. It was not a true ice age of global extent. The Little Ice Age ( LIA) was a period of regional cooling, particularly pronounced in the North Atlantic region. Global average temperatures show that the Little Ice Age was not a distinct planet-wide period but a regional phenomenon occurring near the end of a long temperature decline that preceded the recent global warming. For the most recent period that was much colder than present with significant glaciation, see Last glacial period.
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