Blurred Lines: Are UK seasons becoming less defined?
Temperatures for the UK have increased as a result of climate change (Figure 1).
But what has happened to within year temperature variability? Over the last several years, we have seen beach days in October (BBC article, 2011), snow in spring (Telegraph article, 2016) and heavier rainfall in summer (Met Office blog, 2016)), suggesting an overlap in UK seasons as we previously knew them.
UK fashion houses moving to two seasons
The fashion world is just one industry in the UK that seems to be adjusting to varying temperatures and a subsequent shift in seasons. Summer lines once consisted of shorts and t-shirts and winter collections thick coats, but changing temperatures have blurred the seasonal boundary.
The Italian brand Brioni are an example of this shift. The brand used to have four seasonal lines a year, but now have only two lines each year (Fashion law, 2016): Spring/Summer and Autumn/Winter. The Spring/Summer line starts in January and runs through to June, and the Fall/Winter line is from July through to December.
The onset of seasons earlier than the meteorological calendar is clear, but are these differences simply due to ‘seasonal dressing’ (i.e. a trend of wearing the same fashions year-round due to an increased amount of time in climate-controlled environments) and designers trying to increase their year round profits, or are seasons in the UK actually becoming less distinct?
Are UK temperatures blurring the seasons also?
Using Central England Temperature (CET) records from 1772 to 2014, comparisons have been made between the seasonal averages for each year.
From Figure 4, it can be seen that the temperature differences between seasons Winter/Spring, Spring/Summer and Summer/Autumn have all decreased, on average. The temperature difference between Autumn/Winter shows a slight increase, on average. Temperatures have increased in both autumn and winter from 1772 to 2014, however, the rate of increase is greater in autumn than winter. All comparisons are statistically significant at the 95% confidence level.
Between the years 1772 and 2014, the temperature gap between seasons has, on average, decreased and overall narrowed the definition of seasons.
- Autumn is warming at a greater rate than any other season.
- The greatest similarities between mean temperatures occur between the seasons Winter/Spring and Summer/Autumn.
It would, therefore, seem more sensible for fashion companies to categorise their seasons in a way that embraces changing temperatures i.e. Winter/Spring and Summer/Autumn, rather than Spring/Summer and Autumn/Winter.
Variability within seasons
The findings so far are in support of seasons becoming less defined in terms of yearly average, but how has the variability (spread) of temperatures within each season changed?
By calculating the spread for each of the four seasons on an annual basis, an increase can be seen, on average, between 1997 and 2016 (Figure 3).
With an overall decrease in the temperature difference between seasons over the last several hundred years and an increase in the spread of temperatures within seasons in recent years, it seems fair to conclude that seasons in the UK are indeed becoming less distinct.