FORECASTS OF FUTURE ATMOSPHERIC CO2 CONCENTRATIONS FOR A SIMPLE GLOBAL CARBON-CYCLE MODEL

Our previous theoretical model for a global carbon cycle considering C O2-fertiiization effects of land biota is utilized to forecast future atmospheric CO2 concentrations. Three typical CO2-emission scenarios p repared by the IPCC Working Group I i.e. IS92a, IS92e and IS92e are us ed. A comparison between the present and IPCC predictions for the case of IS92a shows that our model forecasts somewhat lower future atmosph eric CO2 concentrations than the IPCC Working Group. In addition, it i s found that predicted atmospheric CO2 concentrations to about 2020 de pend only very weakly on the adopted emission scenarios and that the a tmospheric CO2 concentration around this year will be about 440 ppmv.