Talk on local climate – Simon Ratsey

Simon grew-up on Cobhay Farm, near Bathealton. His father would wager with him about the temperature exceeding 15.5°C in March, which in the 1950s and 60s was unusual. This led to Christmas presents of a thermometer and rain gauge, and records have been kept of local weather since the 1960s. After Simon left the farm, his father kept the Cobhay records going till 2000 and Simon became responsible for the weather station when teaching at Nettlecombe Court, as well as keeping records at his home in Wellington since 1987. The result has been continuous records of local weather since the 1960s, taken over different overlapping periods at three locations in the same part of Somerset.

30 year periods are normally used to measure climate. Simon has found that the 10-year running average for local annual temperatures is now 1.2°C warmer than in the 1960s, as shown below. This is the equivalent of moving Somerset to Brittany.

10 year temps

As shown in the following chart, early years with big increases in average temperature were 1989 and 1990. This was followed by three low years, which was due to the Mount Pinatubo volcanic eruption in 1991 – the last one to have a significant impact on the world’s weather.

Locally, 2014 was the warmest year Simon has so far recorded. Most above average and higher temperatures have been recorded since 1989, and 2017 looks set to be another unusually warm year.

Temp deviations

Simon’s records of air frosts (0⁰C or below in the thermometer screen 4 feet from ground), show, in the graph below, that they have been decreasing over time. Simon has also worked as a gardener and has noticed that the growing season has extended by about two weeks and some plants that used die off in winter, now continue, including a hardy fuchsia in his garden at home which has still been flowering at some Christmases.

Winter frosts

Looking at other official weather records going back to 1910, many of the warmest months and seasons have occurred since 2000. The four warmest years were 2014, 2011, 2006 and 2007, with the fifth being 1921, an exceptional year that had previously been top of the ranked list for 85 years.

Summers have warmed steadily since 2010s, but are often thought to be less good than previously. This is because summers have also been shown to be duller, with more cloud giving less cooling at night. Overall, local summers have been getting both warmer and wetter.

Local rain in spring and winter appears similar since the 1960s. Local rainfall in the summer appears more variable, with both very wet and very dry summers in recent years. In the autumn, local rainfall appears a bit lower than previously since the early 2000s, and less variable.

Rain can also be more intense. Simon has recorded more days with over 20mm since 1995, with a significant proportion of the year’s total rainfall sometimes arriving on just a dozen or so days. But there have also been summers with few days of intense rain. In 2011 and 2016, Simon recorded no days with more than 20mm of rain from April to September, which he had not previously found in any years going back to the 1960s.

Overall, Simon’s conclusion is that our local weather and climate are changing, with trends towards becoming warmer and wetter, but also with more variability and more days in some years with particularly heavy rain. He also noted that our idea of normal weather has become skewed from what it was. As a gardener and tree-planter, he has seen changes in what varieties grow best and we will increasingly need to take this into account.

See slides presented by Simon Ratsey.

See notes on talk by Gareth Varney.

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