James Croll, FRS, (2 January 1821 – 15 December 1890) was a 19th-century Scottish scientist who developed a theory of climate variability based on changes in the Earth's orbit.

[1] From 1864, Croll corresponded with Sir Charles Lyell,[2] on links between ice ages and variations in the Earth's orbit.

[3] 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",[4] including Climate and Time, in Their Geological Relations in 1875.

Croll further argued that the accumulation of snow would change the pattern of trade winds, leading to the deflection of warming currents like the Gulf Stream, and finally a self-sustaining ice age.

He suggested that when orbital eccentricity is high winters will tend to be colder when the 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.

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.