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Skewness of Temperature Data Implies an Abrupt Change in the Climate System between 1982 and 1993
  • Alasdair Skelton,
  • Nina Kirchner,
  • Ingrid Kockum
Alasdair Skelton
Stockholm University

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Nina Kirchner
University of Stockholm
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Ingrid Kockum
Karolinska Institutet
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Instrumental records of mean annual temperature extend back to the seventeenth and eighteenth centuries at multiple sites in Europe. For such long time series, we expect histograms of mean annual temperature data to become skewed towards higher temperatures with time because of global warming. This occurs, but at 15 of 17 sites, we find that skewness changed abruptly and started increasing rapidly between 1982 and 1993. We argue that this finding may imply an abrupt change in the climate system affecting Europe at that time. One possible cause is a climate tipping point having been passed. Of known tipping elements, we find Arctic sea loss, potentially linked to reduced sulfate aerosol emissions, and coupled to temperature by an albedo or some other feedback mechanism, a likely candidate. This is based on good correlations of sea ice extent and sulfate aerosol emissions with skewness of mean annual temperature data.