One of the most abrupt and yet unexplained CO2 rises found in the ice cores (>10 ppmv in two centuries) occurred during the last deglaciation around 14,600 years ago, quasi-synchronous with the abrupt northern hemispheric warming into the Bølling/Allerød. Here we use U/Th dated atmospheric D14C from Tahiti corals as independent and precise age control for this CO2 rise in combination with carbon cycle simulations to show that the release of old nearly 14C-free carbon might have caused these changes in atmospheric CO2 and D14C. The D14C data also independently constrain the magnitude of the carbon released (100-125 PgC), leading to an atmospheric CO2 peak amplitude of 18–22 ppmv. We here suggest as explanation, in line with CH4 records and terrigenous biomarkers, that not the release of old carbon from the deep ocean, but the release from thawing permafrost in the high northern latitudes might be the source of the abrupt CO2 rise and highlights the potential of this carbon reservoir to modulate climate change via greenhouse-gas feedbacks.