It takes a desert to make ice
Monticello, Jefferson's home, and McCormick Observatory of the University of Virginia are within a few feet in elevation from each other and less than 5 km in distance by crow. A decade of records from Monticello and an equal length of period from McCormick are compared here. Monticello was about 10 F colder in each winter month than our experience at the McCormick Observatory. There were 16.7 more days each winter in which the average temperature failed to climb above the 32 F (0 C) freezing point. At the time Jefferson had collected these weather records, he was remarking on the change in climate toward much warmer conditions and a reduction in temperature extremes. Jefferson was especially sensitive to runs of winter days with cold temperatures. Each winter he had to fill his icehouse.
Jefferson built his icehouse off the north wing of Monticello. Each year He would harvest ice from the backwaters of the Ravenna River that flowed past the base of Monticello, his "little mountain." It took 37 wagonloads of river-ice to fill his ice house. The ice cooled his drinks and kept his food. He made it last all the way through the dog days of summer. He took from winter for his summers.
I have lived in Charlottesville for 4 score and 4 and have seen only two winters with such a deficit of stored calories. Winters where even the small streams froze bank to bank are two in my years (1977-78 and 1978-1979). Ice harvesting and ice house filling might have been possible in those years. The Old Timers around central Virginia mark the first decade of the present century as the time of ice house abandonment. In my backyard there is a circular area of sinking ground. My neighbor, 85 years old in 1972, said there was an ice house on the spot when he was a young boy. Our house was built in 1810. By this time Jefferson had already reported the warming of our climate.
The demise of frozen rivers and home ice houses is testimony to climate change between the 1700s and the present. In 1780, Jefferson began work on the manuscript for his book: Notes on the State of Virginia. In his chapter on climate, he detailed the changes in climate that he and his contemporaries witnessed:
"A change in our climate however is taking place very sensibly. Both heats and colds are become much more moderate within the memory even of the middle-aged. Snows are less frequent and less deep. They do not often lie, below the mountains, more than one, two or three days, and very rarely a week. They are remembered to have been formerly frequent, deep and of long continuance. The elderly inform me the earth used to be covered with snow about three months of every year. The rivers, which then seldom failed to freeze over in the course of the winter, scarcely ever do so now. This change has produced an unfortunate fluctuation between heat and cold, in the spring of the year, which is very fatal to fruits. From the year 1741 to 1769, an interval of twenty-eight years there was no instance of fruit killed by the frost in the neighborhood of Monticello. An intense cold, produced by constant snows, kept the buds locked up till the sun could obtain, in the spring of the year, so fixed an ascendancy as to dissolve those snows, and protect the buds, during their development, from every danger of returning cold. The accumulated snows of the winter remained to be dissolved all together in the spring, produced those overflowing of our rivers, so frequent then, and so rare now."
It is the current "consensus" that temperature extremes like Jefferson's -- "Both heats and colds are become much more moderate within the memory even of the middle-aged." -- are a signature of the 20th century and the most recently tuned GCMs claim it a result of CO2 enrichment of our atmosphere. Apparently and at least in Jefferson's experience the moderating of extremes pre-dates our global experiment with fossil fuels.
Jefferson, T. 1787. Notes on the State of Virginia. Published by John Stockdale, London.
Iran has been in the business of building and operating ice houses (yakhchal)for the past 7,000 years. Click Google “Images” for a Photo grand tour of Iran’s wonderful Ice houses.
“The traditional yakhchal were built at villages on the perimeter of the large deserts on the Central Plateau. Their cone-shaped domes, up to 20 meters high, cover a large open pit for ice storage. The dome is constructed of mud and mud bricks from the excavation of the deep ice pits. An opening at the apex of the dome allows any heat or moisture to escape, and the deep pit uses the ground to moderate the temperature. The ice was either hauled in from nearby mountains or lakes, or produced in open basins at the ice house site.” Hemming Jorgensen’s new book The Ice Houses of Iran.
For additional stories about ice making , go to the CED Index and click on “Aqueous vapors” and Ice “Making Ice at Benares”.
Photo: Pastaitaken, Creative Commons Attribution-Share Alike 3.0 Unported license