The myth of Europe’s Little Ice Age

[TexasTowelie]

The Little Ice Age is generally seen as a major event in European history. Analysing a variety of recent weather reconstructions, this column finds that European weather appears constant from the Middle Ages until 1900, and that events like the freezing of the Thames and the disappearance of English vineyards have simpler explanations than changing climate. It appears instead that the European Little Ice Age is a statistical artefact, where the standard climatological practice of smoothing what turn out to be white noise data prior to analysis gives the spurious appearance of irregular oscillation – a Slutsky Effect.

The Little Ice Age – dated from the mid-14th century to the early 19th – plays a large role in historical analyses. Anthropologist Brian Fagan suggests that this climate swing demoralised the European peasantry, allowing for the rise of despotic leaders (Fagan 2000). British and Dutch canals and rivers frequently froze, allowing French land forces to invade the Netherlands while the Dutch fleet was ice-locked. But was it really an ice age, or have historians been “fooled by randomness” (Taleb 2005)?

In recent research we attempt to discover how much European weather actually worsened during the Little Ice Age. Our conclusion – using a variety of standard temperature reconstructions – is that there is little evidence that a European Little Ice Age ever occurred (Kelly and Ó Gráda 2014).

Figure 1. The European Little Ice Age as Slutsky Effect: Netherlands summer temperature, 1301-1980. The top panel shows the data smoothed with a twenty-five year moving average and gives the appearance of marked cold episodes between the 15th and 19th centuries. The lower panel shows the actual data which are almost entirely random with a constant mean and variance.



Instead, European weather between the 14th and 19th centuries resembles white noise: uncorrelated draws from a distribution with a constant mean and variance (although there are occasional decades of markedly lower summer temperature), with the same behaviour holding more tentatively back to the eleventh century. Our results suggest that the existing consensus over a Little Ice Age in Europe is a statistical artefact, where the standard climatological practice of smoothing what turn out to be random data prior to analysis gives the spurious appearance of irregular oscillations. This is an example of the ‘Slutsky effect’ where filtering of purely random variations can produce spurious cycles.[1]

Read more: http://www.voxeu.org/article/myth-europe-s-little-ice-age