Scotland's Climate Trends Handbook

 
 

Scotland's Climate Trends Handbook describes the changes in weather patterns experienced in Scotland over the last century, with many records extending back to 1910. This text provides some key summary information drawn from across the handbook that focuses on trends since 1961 (usually to 2011). Figure 1 shows the three regions for which we describe the results. Table 1 (click link to view) summarises the results since 1961 for the weather variables.

 

Figure 1 - Map of Scotland showing boundaries of the three regions as defined in this study (North, West and East Scotland).

When we describe areas of Scotland in this handbook, a capital letter is used when any of the three regions are being discussed, that is to say 'North' Scotland rather than 'north' Scotland.

 

Recent climate trends are summarised below.

 

Temperature

 

  • The average temperature has increased for all seasons for all regions by between 1.0 - 1.6 ºC, with a statistically significant trend for spring, summer and autumn.
  • The maximum temperature has increased for all seasons for all regions by between 1.2 - 1.9 ºC, with a statistically significant trend in all seasons.
  • The minimum temperature has increased for all seasons for all regions by between 0.7 - 1.4 ºC, with a statistically significant trend for spring, summer and autumn.
  • Spring has seen the largest temperature increase with Scotland's spring average temperature increasing by 1.5 ºC.
  • The length of winter cold spells reduced by 7.5 days across Scotland, a statistically significant trend.
  • The length of summer heat waves increased by 5.5 days across Scotland, however this was not a statistically significant trend.

 

Frost

 

  • There has been a reduction in the number of days in a year with both air frost and ground frost, by 21 and 29 days respectively for Scotland.
  • The reductions in spring and autumn are statistically significant and reflect a large percentage decline in frost days.
  • There is also a decline in winter frost days, although with frosts more common in winter this is a smaller percentage change and not statistically significant in all regions.

 

Sunshine

 

  • There has been an increase in sunshine during spring and autumn, by 0.6 and 0.3 hours per day respectively for Scotland.
  • There has been little change in sunshine hours during summer or winter.

 

Rainfall

 

  • Average rainfall has increased across Scotland, with an annual increase of 27%, although it varies considerably across seasons and regions.
  • The number of days of rain has changed little. However, there is a statistically significant increase in the annual number of days with heavy rainfall by 8 days for Scotland, ranging between 5 and 12 by region.
  • Winter has seen the largest increase in average rainfall with an increase of 24% in the East and 45 and 51% in the West and North, it is statistically significant for all regions.
  • Spring and autumn rainfall increased by 23% and 25% respectively for Scotland, which are statistically significant trends. However, the trend is not statistically significant for all regions.
  • Although summer rainfall increased for all regions, this was not a statistically significant trend.

 

Snow cover

 

  • Snow cover has decreased for all seasons and regions, with the largest percentage changes in autumn and spring reflecting a shortening of the snow season. Autumn was the only season with a statistically significant trend, with 77% reduced snow cover.
  • Winter has the most snowfall and this has reduced by 24% across Scotland, although this is not a statistically significant trend.
  • There was a lot of year-to-year variability in snow cover.