One of the most useful functions of the Norfolk Record Office is to keep a minutely accurate record of our history, even in the perhaps unexpected field of climate change. A researcher from Bern in Switzerland spent many months looking at medieval Norfolk manorial rolls, in the hope of finding ways to improve weather predictions for the future by studying patterns of the past. About 820 account rolls survive for the period. Made of parchment, they detail the expenses, income and development of agriculture of a manor in one year.
Kathleen Pribyl reconstructed the average temperatures for early spring and summer in Norfolk between 1256 and 1431 by examining the date of the start of the grain harvest. The grain harvest was largely dependent on average temperatures in spring and early summer. The later the harvest began, the cooler the spring and early summer must have been.
Ms Pribyl has tested her theory on average medieval spring/summer temperatures in two ways. First, tree-ring density measurements can give long timescale indications of temperature. Second, she has selected three series of grain harvest dates from Norfolk – 1768-1861, 1803-1828 and 1809-1826 – and compared their data with average temperatures kept in the Central England Temperature series which began in 1650. As expected, the data correlates strongly.
Additionally, she looked at a smaller series of manorial accounts from other Norfolk landowners, namely the Abbey of St Benet’s of Holm and St Giles’s Hospital in Norwich. Her results mean that she has produced the first annual temperature reconstruction for England in the middle ages, showing a cooling trend in the months April to July during the period 1256-1431.
Unfortunately it is not possible to say yet what these mean medieval temperatures were. But it is possible to say that there was ‘pronounced annual variability’. And on a long term basis it would seem that there was a cooling trend in the months April to July during the period 1256-1431.
Another ‘climatologist’ whose work is recorded in the NRO is Robert Marsham, 1708-97. He was born in Stratton Strawless, a scattered village between Norwich and Aylsham. He was so fascinated by the changes occurring each spring that he wrote them down and, on his death, his family carried on his work until 1950. This work has been invaluable to scientists examining climate change.
A transcript of Marsham’s work by Sir John Fenn, entitled Indications of Spring, records the tender appearance of the first snowdrop in 1749 on 4 January, but in 1746 the first snowdrop did not appear until 20 January. We are also told of the first appearance of the swallow, hawthorn and turnip flowers, yellow butterfly, rooks building a nest, mountain ash and horse chestnut in leaf, of course the first cuckoo call, and many other signs.
Marsham even records exotic ‘celestial phenomena’, such as the sighting of a comet in February 1747, two earthquakes in London in February and March 1750, the transit of the planet Venus in June 1761 and an eclipse of the sun in April 1764.