We examine historical contributions of inter fuel substitution, changes in carbon efficiency and energy intensity, growth of economy and population to Korea`s CO_2 emissions from 1970 to 1998 using the log mean weight Divisia index method. The study reveals that economic growth is the most significant factor to CO_2 emissions growth among the five factors. Changes in the fuel substitution and carbon coefficient are found negative contributors to CO_2 emissions growth. Energy intensity, which played dominant role in halting CO_2 emissions growth in the 1980s, began to play reversed role in the 1990s. When evaluated with the log mean Divisia index technique, deterioration of energy intensity in the 1990s is found worse and expected to contribute CO_2 emissions growth further.