The atmospheric concentration of CO 2 increased from 190 to 280 ppm between the last glacial maximum 21,000 years ago and the pre-industrial era. This CO 2 rise and its timing have been linked to changes in the Earth's orbit, ice sheet configuration and volume, and ocean carbon storage. The ice-core record of Í 13 CO 2 (refs,) in the atmosphere can help to constrain the source of carbon, but previous modelling studies have failed to capture the evolution of Í 13 CO 2 over this period. Here we show that simulations of the last deglaciation that include a permafrost carbon component can reproduce the ice core records between 21,000 and 10,000 years ago. We suggest that thawing permafrost, due to increasing summer insolation in the northern hemisphere, is the main source of CO 2 rise between 17,500 and 15,000 years ago, a period sometimes referred to as the Mystery Interval. Together with a fresh water release into the North Atlantic, much of the CO 2 variability associated with the Bølling-Allerod/Younger Dryas period â 1/415,000 to â 1/412,000 years ago can also be explained. In simulations of future warming we find that the permafrost carbon feedback increases global mean temperature by 10-40% relative to simulations without this feedback, with the magnitude of the increase dependent on the evolution of anthropogenic carbon emissions. © 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.