Author, journalist and academic. Born in Forfar, Calder worked as a journalist in Dundee and Glasgow before moving to London. His uplifting book Carry on London (1941) examined the effects of the Blitz and how the towns and cities of Britain, including London, Coventry and Clydebank, continued to function. This brought Calder to the attention of the British Government, yet it is perhaps surprising that a committed socialist and pacifist accepted an appointment as Director of Plans and Campaigns with the newly-formed Political Warfare Executive (PWE), responsible for allied propaganda. In 1942, as part of a secret delegation, he travelled to Washington DC where he met President Franklin Roosevelt. Calder developed propaganda strategies for Operation Torch, the invasion of North Africa (1942), and Operation Overlord, the Normandy landings (1944). He prepared speeches for allied leaders, together with propaganda leaflets and posters.
After the Second World War he worked for various international agencies, such as the United Nations. He wrote widely on subject including global science, atomic energy, race relations and the peace movement, specialising in the public understanding of science, with books such as Living with the Atom (1962), and The Evolution of the Machine (1968).
Serving as Professor of International Relations at the University of Edinburgh (1961-67), Calder was created a life peer in 1966. He was President of the British Peace Council and a founder member of the Campaign for Nuclear Disarmament. He was a friend of socialist author H.G. Wells (1866 - 1946) and Scottish internationalist John Boyd Orr (1880 - 1971) who led the United Nations Food and Agriculture Organisation.
Calder died in Edinburgh. His son was author and historian Angus Calder (1942 - 2008).