Analysis of first air frost of every autumn since 1985.

The Intergovernmental Panel on Climate Change in its report this week reviewed the latest scientific evidence for climate change.
I have analysed the evidence for just one aspect of the climate in Marlborough over the last thirty years, namely the date when the first air frost of autumn occurred since 1985.
Taking the years in groups of five since 1985 and then taking an average, the trend in these averages over the last thirty years can be seen. Using the datum of 1st September the average number of days since that date for the first period of 1985-1989 is 30 days or 30th September.
After a slight regression to 28th September for the next five year average of 1990-1994, the trend is then distinctly later in the year. The average for the first air frost of the year moves to 9th October, 26th October, 27th October and lastly to 1st November for the 2010-2014 group of years.
Although memories are fallible and we remember certain mild autumns that we enjoyed over the recent years, the evidence is quiet clear from the data above that there has been a significant shift to a much later date in the year for the first air frost of autumn.

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