Reidar Nydal was born in 1925 in Flora, Sogn og Fjordane, on the west coast of Norway. Reidar studied physics and mathematics at the University of Oslo and was awarded a master's degree in theoretical physics in 1953. That same year Reidar began work at the newly formed Radiological Dating Laboratory at the Norwegian Institute of Technology (NTH) in Trondheim under the direction of Professor Sverre Westin. In 1960, Reidar became head of the Radiological Dating Laboratory and he continued to direct the laboratory until one year before his retirement in 1995. Reidar received a doctorate from the University of Oslo in 1968, having written a dissertation entitled "An Investigation of Radiocarbon from Nuclear Tests".

Since 1986, Reidar has also served as a professor in the Physics Department at the NTH, where his research has focused on radiological dating. In addition, Reidar's research has focused on the global carbon cycle and the distribution of 14C from nuclear tests in the atmosphere. To facilitate their work, Reidar and other staff (most notably Knut Lövseth) established a worldwide sampling program in the early 1960s to collect measurements in the atmosphere and ocean. Some of these stations have continued collecting measurements for approximately 30 years. Such extended time series are critical for testing global climate models based on CO2. During his distinguished career, Reidar has published 56 radiocarbon-related manuscripts, with roughly half of them related to the carbon cycle and climate. In November 1995, Reidar received the King Harald V gold medal for his radiocarbon work.