An excerpt form Wikipedia:
"The Little Ice Age (LIA) was a period of cooling that occurred after the Medieval Warm Period (Medieval Climate Optimum). While not a true ice age, the term was introduced into the scientific literature by François E. Matthes in 1939. It is conventionally defined as a period extending from the 16th to the 19th centuries, 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. 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."
New Evidence suggest the Little Ice Age was cause be four separate volcanic eruptions during the 13th century between 1275 AD and 1300 AD.
Read the stories here:
Little Ice Age triggered by volcanic eruptions
Four huge volcanic eruptions are to blame for the 'Little Ice Age' that cooled Earth up until the late 19th century
