The Little Ice Age (LIA) was a perio of cooling occurring after a warmer era known as the Medieval Warm Period or Medieval Climate Optimum. Climatologists and historians find it difficult to agree on either the start or end dates of this period. Some confine the Little Ice Age to approximately the 16th century to the mid 19th century. It is generally agreed that there were three minima, beginning about 1650, about 1770, and 1850, each separated by slight warming intervals.