Croll, James (1821–90)

JAMES CROLL WAS a 19th-century Scottish scientist who developed a theory of climate change based on variations in the Earth's orbit. Croll was the leading proponent of an astronomical theory of climate change during the 19th century. Taking into account the precession of the equinoxes, variations in the eccentricity of the orbit, and tilt of the axis, Croll proposed that climate change must be the result of the relation of the Earth to the Sun.

He further speculated, “geological and cosmical phenomena are physically related by a bond of causation.” Although his theory has often been criticized, it influenced the work of Serbian geo-physicist Milutin Milankovic and provided important insights into the interplay of astronomical and geological elements.

James Croll was the second son of David Croll, a stonemason, and Janet Ellis. He was born in the village of Little Whitefield, Perthshire, Scotland, on January 2, 1821. He grew up on a farm and received almost no formal education. However, Croll was attracted to philosophy and science from an early age and began to read widely in those subjects. He initially preferred those two disciplines to geology. Croll held a variety of odd jobs, including tea merchant, innkeeper, insurance salesman, and caretaker at the Andersonian College and Museum in Glasgow. All these jobs allowed Croll to read and write about his favorite subjects. His first book, Philosophy of Theism, was published in 1857, at the age of 36. This was followed by a number of scientific publications on electricity, heat, and most importantly, on astronomical controls on geological climate.

His paper, “On the Physical Cause of the Change of Climate During Geological Epochs,” published in Philosophical Magazine in 1864, provoked the interest of leading scientists in Scotland and England. In [Page 291]this paper, Croll introduced changes in the Earth's orbital elements as periodic and extraterrestrial mechanisms responsible for the beginning of multiple glacial epochs. Croll argued that the eccentricity of the Earth's orbit was sufficiently great to explain every extreme of climatic change evidenced by geology. His theory of ice ages was built on the precession of the equinoxes and variations in the shape of the Earth's orbit. It forecast that one of the two hemispheres would experience an ice age whenever two conditions occur simultaneously: a markedly elongate orbit, and a winter solstice that occurs far from the Sun.