Burroughs claims that there had been almost no depictions of winter in art, and he "hypothesizes that the unusually harsh winter of 1565 inspired great artists to depict highly original images and that the decline in such paintings was a combination of the 'theme' having been fully explored and mild winters interrupting the flow of painting".Wintry scenes, which entail technical difficulties in painting, have been regularly and well handled since the early 15th century by artists in illuminated manuscript cycles showing the Labours of the Months, typically placed on the calendar pages of books of hours.[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 twentieth century levels.The IPCC Fourth Assessment Report (AR4) of 2007 discusses more recent research, giving particular attention to the Medieval Warm Period.
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." but a series of events before the known climatic minima has often been referenced.
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.
Evidence 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.
Based on radiocarbon dating of roughly 150 samples of dead plant material with roots intact, collected from beneath ice caps on Baffin Island and Iceland, Miller et al.
(2012) The first River Thames frost fair was in 1607 and the last in 1814; changes to the bridges and the addition of the Thames Embankment affected the river flow and depth, greatly diminishing the possibility of further freezes.