Europe’s Little Ice Age

Two economists from University College Dublin question its existence.

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. 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”?

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. ….

Given the lack of evidence for any sustained trends or shifts in European temperatures before 1900, how are we to account for the general belief among climatologists that Europe experienced a Little Ice Age? The answer probably lies in the practise in climatology of smoothing data using some sort of moving average before analysing it. If the underlying data are white noise, as European temperatures appear to be, then smoothing them will give the spurious appearance of irregular oscillations as the filter is distorted by runs of high or low values: a Slutsky effect. ….

Note when interpreting our results that local weather conditions are a noisy signal of global ones. Just as the fact that European temperatures did not rise much during the twentieth century does not imply that global temperatures were constant (rises were concentrated in the Arctic and Siberia), so their constancy between the 14th and 19th centuries does not imply that global average temperatures did not experience notable falls during this time associated primarily with known falls in solar output. [Emphasis added.]

Morgan Kelly and Cormac Ó Gráda, “The myth of Europe’s Little Ice Age“, VoxEU, 28 March 2015 (ungated).

Here is the full, peer-reviewed paper that the Vox column summarizes:

Morgan Kelly and Cormac Ó Gráda, “Change points and temporal dependence in reconstructions of annual temperature: Did Europe experience a Little Ice Age?“, Annals of Applied Statistics 8:3 (November 2014), pp. 1372-1394 (ungated link).

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