The effects of a large igneous province on the concentration of atmospheric carbon dioxide (P-CO2) are mostly unknown. In this study, we estimate P-CO2 from stable isotopic values of pedogenic carbonates interbedded with volcanics of the Central Atlantic Magmatic Province (CAMP) in the Newark Basin, eastern North America. We find pre-CAMP P-CO2 values of similar to 2000 parts per million (ppm), increasing to similar to 4400 ppm immediately after the first volcanic unit, followed by a steady decrease toward pre-eruptive levels over the subsequent 300 thousand years, a pattern that is repeated after the second and third flow units. We interpret each P-CO2 increase as a direct response to magmatic activity (primary outgassing or contact metamorphism). The systematic decreases in P-CO2 after each magmatic episode probably reflect consumption of atmospheric CO2 by weathering of silicates, stimulated by fresh CAMP volcanics.