HE WAS the janitor who unlocked the secret of how ice ages happen. The sickly son of a poor Scottish farmer, James Croll left school at 13 and became an itinerant labourer and failed salesman. But decades of private reading and an astonishing capacity for original thought saw him soar to scientific stardom. Croll became the father of climate-change research, and corresponded as an equal with the science heavyweights of the day, including Charles Darwin, Lord Kelvin, Arctic explorer Fridtjof Nansen and geologist Charles Lyell. Yet you have probably never heard of him.
His star waned, and his insights about the cosmological causes of the great glaciations sank from view, until revived half a century later by Serbian mathematician Milutin Milankovitch, who took the plaudits. Croll died in penury, a footnote even on his own gravestone. Was he a victim of Victorian snobbishness? Or might he have fared even worse had he lived in the modern age?
Croll was born in 1821 and raised on a smallholding on moorland in rural east Scotland, land he worked from a young age. His sporadic schooling ended at 13, but by then he had stumbled across a copy of The Penny Magazine, the 快猫短视频 of its day. He became hooked on science. By 14, he was reading the great science texts of the time. 鈥淎t first I became bewildered, but soon the beauty and simplicity of the conceptions filled me with delight and astonishment,鈥� he later wrote in an . 鈥淚 studied pneumatics, hydrostatics, light, heat, electricity and magnetism. I obtained assistance from no one.鈥�
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His head was full of ideas, but Croll had no qualifications and no money. At 16, he was a travelling millwright, sleeping in rat-infested barns. Later he became a joiner, before a damaged elbow left him unable to do manual work. He was also, as his step-nephew James Campbell Irons wrote in a biographical appreciation, 鈥渉eavy and ungainly鈥� as well as 鈥渕odest, shy, dry and with an almost speechless manner鈥�.
Not surprisingly, then, Croll also failed as a tea merchant and an insurance salesman, and went bankrupt as the landlord of a temperance hotel in a town of 3500 people and 16 taverns. By luck, he eventually found himself a neighbour of the head of Anderson鈥檚 University, the forerunner of Strathclyde University. Croll became its caretaker. There, duties done, he would hole up in the library, pursuing the great scientific issues of the day. One of those was the cause of the ice ages.
Geologists had deduced that large parts of Europe had been repeatedly covered in ice, but nobody knew what caused this waxing and waning. There were some theories rooted in astronomical phenomena, but it was Croll鈥檚 untutored, free-ranging mind that would crack the conundrum.
By painstaking calculation, he showed that over more than a million years, the glaciations appeared to coincide with the periodic extremes of what astronomers call eccentricity. This variation in the elliptical shape of Earth鈥檚 orbit around the sun has only a tiny effect on the total amount of solar radiation reaching the planet. In his greatest insight, Croll proposed that it was enough to trigger substantial indirect cooling of the Arctic 鈥� in particular by the diversion of the Gulf Stream, reducing heat reaching the pole. As more ice formed, more sunlight was reflected, causing more cooling. Such amplifying feedbacks underpin estimates of the impact of human-made climate change today.
His ideas were , a top UK science journal of the day. The paper was attributed to 鈥淛ames Croll, Anderson鈥檚 University鈥�. Whether the editors knew Croll was a janitor is not recorded, but soon it didn鈥檛 matter. As Croll put it, 鈥渢he paper excited a considerable amount of attention鈥�.
He was soon corresponding with the great and the good of science. Darwin wrote: 鈥淚 have never, I think, in my life, been so deeply interested by any geological discussion.鈥� Croll鈥檚 paper had, he said, 鈥渃leared so much mist from before my eyes鈥�.
In 1867, Croll became secretary of the Scottish Geological Survey in Edinburgh. It allowed him time, despite growing bouts of poor health, to produce a book on his thinking. Published in 1875, Climate and Time appeared to seal his reputation as one of the era鈥檚 great scientists. Within months, he had an honorary degree from the University of St Andrews, and fellowships at the Royal Society in London and the New York Academy of Sciences.
Croll published more groundbreaking research: on how glaciers moved, the causes of ocean circulation, and the thickness of Antarctic ice 鈥� at a time when scarcely anyone had even set foot on the continent. He also persuaded Darwin that rivers were important agents of erosion.
The high waters of Croll鈥檚 fame retreated as he became ever more reclusive. Turning down an invitation to lecture at the British Association (today the British Science Association), he wrote: 鈥淚 dislike all such public displays鈥� there is a cold materialistic atmosphere around scientific men in general that I don鈥檛 like. I mix but little with them.鈥�
His health worsening, he retired in 1880, aged 59. Prime ministers William Gladstone and Lord Salisbury both rebuffed pleas from Darwin, Lord Kelvin and others to give Croll a full civil-service pension. He ended up penurious in rented lodgings in Perth, just streets away from where he bought his first Penny Magazine. He died a decade later. He was buried in what is now an abandoned churchyard in Cargill. A worn gravestone lists 14 of his forebears, with Croll and his wife Isabella mentioned last, in the smallest letters, as space on the stone ran out.
鈥淎n astonishing capacity for original thought saw him soar to scientific stardom鈥�
One obituary called him 鈥渁mong the foremost, if not the first [investigator] of the physical cause of climatic change鈥�. But by then, the salons of science had tired of this testy recluse. Soon, his name and his theories were largely forgotten.
Only in the 1930s were they revived by Milankovitch, who corrected some inaccuracies in what he called Croll鈥檚 鈥渕ost remarkable鈥� work. Even so, when ocean-sediment cores taken in the 1970s confirmed the causal links deduced by Croll, the Scot was so forgotten that Earth鈥檚 periodic coolings became known as Milankovitch cycles.
In the past decade, a handful of Scottish academics have tried to rescue Croll鈥檚 name. There is now a memorial to him outside the Royal Scottish Geographical Society in Perth.
Croll鈥檚 fall is usually painted as the result of Victorian sniffiness at the untutored working class. Maybe so. But what is remarkable, says Andrew Dlugolecki at the University of East Anglia, UK, is how much respect he did receive in his heyday, despite his lack of formal qualifications. 鈥淟eading scientists corresponded with Croll as an equal. That would probably be impossible nowadays, given the huge emphasis placed on papers in the scientific literature,鈥� says Dlugolecki.
And what journal today would publish a paper, whatever its merits, from a janitor with no formal education? 快猫短视频 asked Nature whether its editors could think of such an upstart in their recent archives. They could not.
This article appeared in print under the headline 鈥淐aretaker who solved the ice age mystery鈥�
