Variations in the Earth’s Rotation Rate, 1820–1970

Variations in the rate of rotation of the earth have been measured for many years with increasing precision as new instruments became available. The quality of the primary sources of the observations used to compile these data varies considerably over the 151 year period from 1820–1970. Luo, Liang, Ye, Yan and Li (1977) take their data from Brouwer (1952) and in order to produce a plot of homogeneous appearance, different sets of smoothing have been applied over the periods 1820–1922 and 1923–1956. The data are reproduced in Table 20.1.