James Croll
Encyclopedia
James Croll was a 19th century Scottish
scientist
who developed a theory of climate
change based on changes in the Earth's orbit
.
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
, 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", 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.
), 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 age
s 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.
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
scientist
Scientist
A scientist in a broad sense is one engaging in a systematic activity to acquire knowledge. In a more restricted sense, a scientist is an individual who uses the scientific method. The person may be an expert in one or more areas of science. This article focuses on the more restricted use of the word...
who developed a theory of climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
change based on changes in the Earth's orbit
Planetary orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
.
Life
James Croll was born in 1821 on the farm of Little Whitefield, near WolfhillWolfhill
Wolfhill is a small Hamlet in Perthshire with a population of 316 . Formerly known as Carolina, it was given the nickname of "Snipetown" many years ago by locals, owing to the high numbers of snipes that used to inhabit the area....
in Perthshire
Perthshire
Perthshire, officially the County of Perth , is a registration county in central Scotland. It extends from Strathmore in the east, to the Pass of Drumochter in the north, Rannoch Moor and Ben Lui in the west, and Aberfoyle in the south...
, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
(NO1733
British national grid reference system
The Ordnance Survey National Grid reference system is a system of geographic grid references used in Great Britain, different from using latitude and longitude....
). He was largely self-educated, teaching himself physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
and astronomy
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
. At 16 he became an apprentice wheelwright
Wheelwright
A wheelwright is a person who builds or repairs wheels. The word is the combination of "wheel" and the archaic word "wright", which comes from the Old English word "wryhta", meaning a worker or maker...
at Collace near Wolfhill, and then because of health problems a tea merchant in Elgin
Elgin, Moray
Elgin is a former cathedral city and Royal Burgh in Moray, Scotland. It is the administrative and commercial centre for Moray. The town originated to the south of the River Lossie on the higher ground above the flood plain. Elgin is first documented in the Cartulary of Moray in 1190...
, Moray
Moray
Moray is one of the 32 council areas of Scotland. It lies in the north-east of the country, with coastline on the Moray Firth, and borders the council areas of Aberdeenshire and Highland.- History :...
. He married Isabella Macdonald in 1848.
In the 1850s he managed a temperance
Temperance movement
A temperance movement is a social movement urging reduced use of alcoholic beverages. Temperance movements may criticize excessive alcohol use, promote complete abstinence , or pressure the government to enact anti-alcohol legislation or complete prohibition of alcohol.-Temperance movement by...
hotel in Blairgowrie
Blairgowrie and Rattray
Blairgowrie and Rattray and Raitear is possibly from an English language cognate of Gaelic ràth, meaning fortress + a Pictish term cognate with Welsh tref, meaning settlement) is a twin burgh in Perth and Kinross, Scotland. Amongst locals, the town is colloquially known simply as "Blair"...
, and was then an insurance agent in Glasgow
Glasgow
Glasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...
, Edinburgh
Edinburgh
Edinburgh is the capital city of Scotland, the second largest city in Scotland, and the eighth most populous in the United Kingdom. The City of Edinburgh Council governs one of Scotland's 32 local government council areas. The council area includes urban Edinburgh and a rural area...
and Leicester
Leicester
Leicester is a city and unitary authority in the East Midlands of England, and the county town of Leicestershire. The city lies on the River Soar and at the edge of the National Forest...
. 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
Charles Lyell
Sir Charles Lyell, 1st Baronet, Kt FRS was a British lawyer and the foremost geologist of his day. He is best known as the author of Principles of Geology, which popularised James Hutton's concepts of uniformitarianism – the idea that the earth was shaped by slow-moving forces still in operation...
, 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
British Geological Survey
The British Geological Survey is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS headquarters are in Keyworth, Nottinghamshire, but other centres...
, as keeper of maps and correspondence, where the director, Sir Archibald Geikie
Archibald Geikie
Sir Archibald Geikie, OM, KCB, PRS, FRSE , was a Scottish geologist and writer.-Early life:Geikie was born in Edinburgh in 1835, the eldest son of musician and music critic James Stuart Geikie...
, encouraged his research. He published a number of books and papers which "were at the forefront of contemporary science", including Climate and Time, in Their Geological Relations in 1875. He corresponded with Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
on erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
by rivers.
In 1876, he was elected Fellow of the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...
, and awarded an honorary degree by the University of St Andrews
University of St Andrews
The University of St Andrews, informally referred to as "St Andrews", is the oldest university in Scotland and the third oldest in the English-speaking world after Oxford and Cambridge. The university is situated in the town of St Andrews, Fife, on the east coast of Scotland. It was founded between...
. He retired in 1880 because of ill health, and died in 1890.
Theory of ice ages
Using formulae for orbital variations developed by Leverrier (which had led to the discovery of NeptuneNeptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
), 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
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
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 age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
s 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
Niagara Falls
The Niagara Falls, located on the Niagara River draining Lake Erie into Lake Ontario, is the collective name for the Horseshoe Falls and the adjacent American Falls along with the comparatively small Bridal Veil Falls, which combined form the highest flow rate of any waterfalls in the world and has...
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.
Works
- 1857: The Philosophy of Theism
- 1875: Climate and Time, in Their Geological Relations
- 1885: Climate and Cosmology
- 1896: posthumous publication of Autobiographical Sketch of James Croll, With Memoir of His Life and Work, edited by J. C. Irons