We used NAO index data from the Climate Research Unit University of East Anglia (undated) and Osborn (undated) as these comprise a long and definitive record (Table 1). The longest data series of Scottish snow cover is from UK Met Office stations which record snow presence at a given point at 09:00 hours UTC each morning; the longest of these is Braemar which has recorded since 1927 (Harrison et al. 2001). Ninety-six per cent of UK Met Office snow recording stations lie below 300 m elevation (Spencer et al. 2014) and so are unrepresentative of the 31% of Scottish landmass that is higher (Spencer et al. 2014). These UK Met Office station data are used by proxy via the UK Climate Projections 2009 (UKCP09) snow cover data set (Met Office undated). Table 1 shows a non-definitive list of Scottish snow cover data sets, which are all used within this study.