Temperature related variables

Growing season start and end dates

 
 

Figure 16 - Growing season a) start dates (days from 1 January) and b) end date (days from 1 January) for Scottish region from 1961 to 2004, with smoothed curves showing a running average.

Table 9 - Changes in growing season start and end (in days) 1961 to 2004 (A negative number of days shows a date earlier in the year, in other words, the growing season starting earlier in the year). Values in bold shows that we are 95% confident (statistically) that the change is part of a measurable trend.

 

North Scotland East Scotland West Scotland Scotland
Growing season start (in days) -19.6 -20.6 -22.4 -20.7
Growing season end (in days) 11.5 12.0 14.4 12.5

 

 

Regional trends

 

  • The growing season is starting almost three weeks earlier in North and East Scotland, and more than three weeks earlier in the West.
  • While the growing season is also ending later, it is by less than two weeks in the North and East and just over two weeks in the West.
  • The changes to the start and end of the growing season are part of a clear trend in all regions.

Spatial trends

 

  • The pattern of change for the start and end of the growing season is similar to that for the length of the growing season.
  • Coastal areas show a greater tendency towards an earlier start and later end to the growing season than central Scotland.
  • We have already seen the longer growing season, and in particular the earlier start, through a change in flowering dates of plants, particularly those flowering in early spring (Roberts et al., 2004).

Future trends

 

  • The UKCIP02 scenarios suggest that by the 2050s the growing season may start one to three weeks earlier and end by one to three weeks later.
  • The estimates for the start of the growing season are similar to those we have seen, but suggest a later end to the growing season than we have seen already.

 

Figure 17 - Pattern of change in the start (left panel) and end (right panel) of the growing season (in days), from 1961 to 2004. Negative values show the season starting or ending earlier.