A linear systems analysis of the Mauna Loa carbon dioxide data is presented using estimated fossil carbon dioxide production as input and observed yearly means of carbon dioxide in the atmosphere as output. The analysis is done on discrete time basis with 1 year as a time step. Because of the near exponential increase in fossil fuel production, not much information is possible to extract from the data concerning system parameters except that at present, 50-60% of the atmosphere "excess" carbon dioxide is transferred to the earth's surface yearly (the oceans and land surfaces). However, the results indicate that the pre-industrial equilibrium level of atmospheric carbon dioxide may have increased to a new "equilibrium" level about 10 per mille higher. This can, however, be due to the slow exchange rate between deep sea water and the more superficial parts, the parameter of which is not possible to deduce from the available set of input-output data.