| James Croll | |
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| Born | January 2, 1821 |
| Died | December 15, 1890 (aged 69) |
| Nationality | Scottish |
| Occupation | Scientist |
| Spouse(s) | Isabella Macdonald (m. 1848–1890) |
James Croll (2 January 1821 – 15 December 1890) was a 19th century Scottish scientist who developed a theory of climate change based on changes in the Earth's orbit.
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James Croll was born in 1821 on the farm of Little Whitefield, near Wolfhill in Perthshire, Scotland (NO1733). He was largely self-educated, teaching himself physics and astronomy. At 16 he became an apprentice wheelwright at Collace near Wolfhill, and then because of health problems a tea merchant in Elgin, Moray. He married Isabella Macdonald in 1848.
In the 1850s he managed a temperance hotel in Blairgowrie, and was then an insurance agent in Glasgow, Edinburgh and Leicester. In 1859 he became a caretaker in the museum at the Andersonian College and Museum, Glasgow, so as to have access to books to allow him to develop his ideas.
From 1864, Croll corresponded with Sir Charles Lyell[1], on links between ice ages and variations in the Earth's orbit. This led to a position in the Edinburgh office of the Geological Survey of Scotland, as keeper of maps and correspondence, where the director, Sir Archibald Geikie, encouraged his research. He published a number of books and papers which "were at the forefront of contemporary science"[2], including Climate and Time, in Their Geological Relations in 1875. He corresponded with Charles Darwin on erosion by rivers.
In 1876, he was elected Fellow of the Royal Society, and awarded an honorary degree by the University of St Andrews. He retired in 1880 because of ill health, and died in 1890.
Using formulae for orbital variations developed by Leverrier (which had led to the discovery of Neptune), Croll developed a theory of the effects of variations of the Earth's orbit on climate cycles. His idea was that decreases in winter sunlight would favour snow accumulation, and for the first time coupled this to the idea of a positive ice-albedo feedback to amplify the solar variations. He suggested that when orbital eccentricity is high, then winters will tend to be colder when earth is farther from the sun in that season and hence, that during periods of high orbital eccentricity, ice ages occur on 22,000 year cycles in each hemisphere, and alternate between southern and northern hemispheres, lasting approximately 10,000 years each.
Croll's theory predicted multiple ice ages, asynchronous in northern and southern hemispheres, and that the last ice ages should have ended about 80,000 years ago. Evidence was just then emerging of multiple ice ages, and geologists were interested in a theory to explain this. Geologists were not then able to date sediments accurately enough to determine if glaciation was synchronous between the hemispheres, though the limited evidence more pointed towards synchronicity than not. More crucially, estimates of the recession rate of the Niagara Falls indicated that the last ice age ended 6,000 to 35,000 years ago - a large range, but enough to rule out Croll's theory, to those who accepted the measurements.
Croll's work was widely discussed, but by the end of the 19th century, his theory was generally disbelieved. However, the basic idea of orbitally-forced insolation variations influencing terrestrial temperatures was further developed by Milutin Milankovitch and eventually, in modified form, triumphed in 1976.
JAMES CROLL (1821-1890), Scottish man of science, was born of a peasant family at Little Whitefield, in the parish of Cargill, in Perthshire, on the 2nd of January 1821. He was regarded as an unpromising boy, but a trifling circumstance aroused a passion for reading, and he made great progress in self-education. He was apprenticed to a wheelwright at Collace in Perthshire, but being debarred by ill-health from manual labour, he became successively a shop-keeper and an insurance agent. In 1859 he was made keeper of the Andersonian Museum in Glasgow, a humble appointment, which, however, gave him congenial occupation. In 1857, being deeply impressed by the metaphysics of Jonathan Edwards, he had published an anonymous volume entitled The Philosophy of Theism; but his connexion with the Museum induced him to take up physical science, and from 1861 onwards he studied with such perseverance that he was enabled to contribute papers to the Philosophical Magazine and other journals. For that magazine in 1864 he wrote his celebrated essay "On the Physical Cause of the Changes of Climate during Geological Epochs." This led to his receiving an appointment on the Scottish Geological Survey in 1867, and for thirteen years he took charge of the Edinburgh Office. In 1875 he summed up his researches upon the ancient condition of the earth in his Climate and Time, in their Geological Relations, in which he contends that terrestrial revolutions are due in a measure to cosmical causes. This theory excited warm controversy. Croll's replies to his opponents are collected in his Climate and Cosmology (1885). He had been compelled by ill-health to withdraw from the public service in 1880; yet, working under the greatest difficulties, and harassed by the inadequacy of his retiring pension, he managed to produce Stellar Evolution, discussing, among other things, the age of the sun, in 1889; and The Philosophical Basis of Evolution, partly a critique of Herbert Spencer's philosophy, in 1890. He died on the r 5th of December 1890. The soundness of Croll's astronomical theory regarding the glacial period has since been criticized by E. P. Culverwell in the Geological Magazine for 1895, and by others; and it is now generally abandoned. Never theless it must be admitted that his character as a scientific worker under great discouragements was nothing less than heroic. The hon. degree of LL.D. was conferred on him in 1876 by the university of St Andrews; and he was elected F.R.S. in the same year.
An Autobiographical Sketch of James Croll, with Memoir of his Life and Work, was prepared by J. C. Irons, and published in 1896.
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Categories: CRO-CUN | Earth scientists
   | James Croll - unsung scientist - Overview of James Croll |
| | Index of some of Croll's correspondence - Croll | James | 1821-1890 | physical geologist and Keeper of Maps and Correspondence, Geological Survey of Scotland |
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