He was one of 10 children of Rev. Gilbert Sparshott Karney, Rector of Emmanuel Church, Hampstead and Emma Sarah Storrs. He was educated at Haileybury and Trinity College, Cambridge, where he graduated B.A. in 1896.
He married Georgina Maude Bessie Fielding in Buenos Aires in 1908 and they had 7 children, Peter, Anthony (Tony), Audrey. George, Rosamund, Mary (Molly), and Grace.
He was ordained in the Church of England in 1897 and appointed assistant chaplain to the Missions to Seamen at Sunderland. In 1903 he was Rector of Woolpit in Suffolk in 1903. He had become fascinated in the work of seamen and was sent to work on the staff of the Seaman's Institute in San Francisco then one of the toughest assignments because of the number and state of the seamen arriving after the stormy voyage around Cape Horn. He became involved in protecting young seamen from being 'shanghaied' or 'crimped' and acquired the name of the fighting parson. The San Francisco Institute was destroyed by the earthquake in 1905. In 1906 he was Chaplain to the Missions to Seamen in Buenos Aires.
In 1914, on the outbreak of the First World War he became a chaplain in the Royal Navy firstly on a hospital ship and then with pastoral care for a whole squadron. In early 1918 he came chaplain with the 22nd Northumberland Fusiliers when they were overrun in the German March offensive and in the interests of protecting his men he was taken into captivity at the detention camp in Karlsruhe. From 1918 to 1922 he was Oxford Diocesan Missioner. In 1922 he was awarded an honorary D.D. by the University of Cambridge.
On 25 July 1922 he was consecrated first Bishop of Johannesburg. The new cathedral (St Mary's), which bears his name on the foundation stone, was built in a poor downtown area to serve ALL the people of the Johannesburg. He spent a considerable period of his ministry seeking better conditions for the "native" population. A card bearing the words "ALL RACES WELCOME - ARTHUR + " was pinned in the cathedral and remained there for some 50 years. He also instituted services for black congregations in their own languages. In Bishop Karney's first ten years not only was the fine cathedral consecrated but 25 churches had been built. During his first five years the number of black children in diocesan schools rose from just over 5,000 to more than 9,000. In 1931 karney wrote "Alas the Native cant bargain - at least he can if he gets a great leader but he hasn’t found one yet". In that month Desmond Tutu, later to succeed Karney as Bishop of Johannesburg, was born and the young Nelson Mandela was tending cattle in the hills above Qunu in the Transkei.
He became Bishop of Southampton from 1933 to 1943, Chaplain of Marlborough College until 1944 and Rector of Blendworth until 1949.Following his retirement he lived in Lewes, Sussex until his death in 1963.
He wrote a number of books:
- Christ's Treasure House
- The Father And His Sons
- An Ambassador in Chains
- God in the Bible
Two of his sons went into the Church. Peter was Chaplain of Trinity College, Cambridge, a Naval Chaplain during the war and vicar of Embleton, Northumberland. Tony was Chaplain to the Church Railway Mission in South Africa and Rector of Eythorne, Kent.
- The Times, 9 December 1963