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inglese Little Ice Age , LIA) è un periodo di tempo che va dall'inizio del XIV secolo alla metà of the nineteenth century [1] [2] [3] where there was a sudden fall in temperature land in 'northern hemisphere . This period was preceded by a long period of relatively high temperatures called Medieval Warm Period . Since 1300
has witnessed a gradual progress of glaciersup to a maximum expansion around the 1850 when temperatures started to increase favoring the withdrawal of the ice. This phase is currently underway and if there will be a change in the near future many glaciers disappear. At first it was believed that the Little Ice Age was a global phenomenon, but now we tend to doubt it. For example, the reconstruction of Northern Hemisphere mean temperatures over the last 1000 years does not show a pronounced cooling. From the data collected it appears that in this period average temperatures are lowered only 1 ° C
about.[4] The debate about the extent of this cooling, as well as the previous heating medieval remains still open and unfinished.
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The Little Ice Age caused , but are documented in detail only Europe and North America . In the mid-seventeenth century glaciers in the Swiss Alps advanced gradually incorporating farms and destroying entire villages. [5] River Thames
of rivers and canals of the Netherlandsoften froze during the winter and even shoes and people held fairs on the ice. [5] In the winter of 1780 the New York Harbor froze, allowing people to walk from Manhattan to Staten Island. The sea ice surrounding the ' Iceland extended for miles in all directions, preventing access to naval ports of the island. So also in Greenland . In both countries commercial ships from Denmark could not penetrate the earth. This meant that Denmark began to forget the existence of the two islands. We have references 1500 a Danish expedition to Greenland he found completely deserted. In particular, we are reminded of the 'Winter 1709, according to experts, is considered the coldest in 500 years to the European continent. The coldest winters had effects on human life in large and small size. The
famines became more frequent (than the 1315killed 1.5 million people) and deaths from the disease increased. The Little Ice Age can be seen in works of art at the time, for example, dominates the snow many landscapes by the Flemish painter Pieter Brueghel the Elder , who lived between 1525 and 1569. Cause
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Scientists have identified some possible causes for the predominant Little Ice Age: The solar . However, in the absence of the elements certain and absolute, there are many other hypotheses that attempt to explain its causes. Various clues emerged as another cause of the Little Ice Age (and the ice ages in general) can be represented by a slowdown in
Gulf Stream and other ocean currents.[6] [7] [8] This current contributes to the mild climate of the Western Hemisphere, it seems that during periods of total glaciation of the planet all the ocean currents had been arrested, and the Little Ice Age may have been caused only by a temporary slowdown of the Gulf Stream, [9] [10] [11] combined with a decrease in solar activity. It is not yet known whether these phenomena are interrelated. Although there are several hypotheses, none of them are still reasonable shared by the scientific community.
It seems, moreover, that a new possible slowdown of the Gulf Stream could influence the global climate or continental within a relatively short period.[12]
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 Main article: | solar activity. |
1715, its central range of the Little Ice Age, the sunspots were found unusually few, a few years without detection of any stain (l ' observation of sunspots and their cataloging began around 1610, a few years after the invention of the telescope ). This period of few sunspots is also known as the Maunder Minimum and fits with the period more rigid during the Little Ice Age. It must be said that is not currently known no direct connection between low sunspot number and low-temperature terrestrial [14] [15] but this coincidence suggests that the connection can be. Other indicators of low solar activity during this period are represented by the levels of carbon beryllium -14 and -10. [16] Recent studies by studying ice cores taken from Greenland have led to the Maunder Minimum of the last 1000 years studying '
isotope of beryllium, and this is created by the interaction of cosmic rayswith ice. These studies suggest that variations in solar activity affect Earth's climate in some way causing heating and cooling. As a result, these data further show that the sun has never been so active in the last millennium, as in the past 60 years. [ citation
The Rhone Glacier a century ago (1890-1900). 
[edit ] During the Little Ice Age the world has experienced an increase in volcanic activity.
[17]When a volcano erupts , his ashes reach the tops of the ' atmosphere and from there expand to the entire Earth . These clouds of ash can block part of solar radiation, causing a cooling of the climate that can last up to two years by the eruption. The eruptions also emit sulfur form of gas SO 2 . When this gas reaches the stratosphere turns into sulfuric acid particles that reflect sunlight, thus increasing the reduction of solar radiation reaching the Earth's soil. The eruption of the volcano in 1815
Tambora in Indonesia whitewashed the atmosphere with his ashes, the following year, 1816 , is known as the 'year without summer : frost and snow were reported in June and July both in New England and North Europe. [5] End of Little Ice Age
[edit ] The Little Ice Age ended around 1850
, when the Earth's climate began to warm up gradually. Clear evidence of the increase in temperature during the last 150 years is impressive retreat of glaciers in nearly all the glaciers in the world.A spectacular example of this phenomenon is visible in the upper
Rhone Valley.
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