The Little Ice Age was a period from about 1550 to 1850 when the world experienced relatively cooler temperatures compared to the present. Subsequently, until about 1940, glaciers around the world retreated as the climate warmed substantially. Glacial retreat slowed and even reversed temporarily, in many cases, between 1950 and 1980 as global temperatures cooled slightly.
It is difficult to overstate how stupid this line of thinking is.
They claim that glaciers melted as the climate warmed rapidly from 1850 to 1940, but then a slight cooling after 1940 caused glaciers to advance. The theory they are promoting is that the freezing point of water is controlled by whether temperatures are increasing, or decreasing – not the absolute temperature. That is just plain idiotic.
Humans surpassed this level of ignorance hundreds of years ago, until brain-dead climate science became prominent. These really are the world’s stupidest people.