A model scenario for the change in global marine biogenic CaCO3 export production (CaCO3 = calcium carbonate) due to increasing atmospheric carbon dioxide partial pressure is carried out. Findings from laboratory experiments, which suggest a decrease of biocalcification at higher pCO2, are extrapolated to the world ocean by use of the biogeochemical ocean general circulation model HAMOCC. For an A1B IPCC emission scenario and constant emission rates after year 2100, the simulation predicts a global decrease of biological CaCO3 export production by about 50% in year 2250. The negative feedback due to this drop in CaCO3 export on the atmospheric CO2 concentration is small as compared to the anthropogenic CO2 emissions. This negative feedback will potentially be compensated by a shallower remineralization of organic carbon.