Guy Stewart Callendar (1898–1964) is noted for identifying, in 1938, the link between the artifcial production of carbon dioxide and global warming. Today this is called the “Callendar Efect. ” He was one of Britain’s leading steam and combustion engineers, a specialist in infrared physics, author of the standard reference book on the properties of steam at high tempe- tures and pressures, and designer of the burners of the notable World War II airfeld fog dispersal system, FIDO. He was keenly interested in weather and climate, taking measurement so accurate that they were used to correct the ofcial temperature records of central England and collecting a series of worldwide weather data that showed an unprecedented warming trend in the frst four decades of the twentieth century. He formulated a coherent theory of infrared absorption and emission by trace gases, established the nineteenth-century background concentration of carbon dioxide, and - gued that its atmospheric concentration was rising due to human activities, which was causing the climate to warm. Callendar’s contributions to climatology led the way in the mid-twentie- century transition from the traditional practice of gathering descriptive c- mate statistics to the new and exciting feld of climate dynamics. In the frst half of the twentieth century, the carbon dioxide theory of climate change xiv Introduction had fallen out of favor with climatists.