A high-resolution record of atmospheric carbon dioxide (CO₂) concentrations from 650,000 to 800,000 years before present (BP) has been obtained from the EPICA Dome C ice core in Antarctica. This record extends the previously known CO₂ levels by two complete glacial cycles, providing a more comprehensive understanding of past atmospheric CO₂ levels. The data show a strong correlation between CO₂ concentrations and Antarctic temperatures over eight glacial cycles, but with significantly lower concentrations between 650,000 and 750,000 years BP. The lowest CO₂ concentration measured in an ice core, 172 p.p.m.v., was found during Marine Isotope Stage (MIS) 16, reflecting enhanced oceanic carbon storage. The record also reveals a natural range of CO₂ concentrations from about 170 to 300 p.p.m.v. during the late Quaternary, with a gradual increase of about 8 p.p.m.v. per thousand years to 190 p.p.m.v. at 665 kyr BP. The study involved two deep ice cores drilled in Antarctica, with measurements conducted using various techniques, including laser absorption spectroscopy and gas chromatography. The data show a consistent record of CO₂ levels, with some variations due to measurement artifacts. The record also highlights significant fluctuations in CO₂ levels during different glacial and interglacial periods, with a notable shift in the CO₂/temperature relationship after MIS 16. This shift is not explained by temperature overestimation but may indicate a long-term increase in CO₂ levels from 800 to 400 kyr BP, influenced by changes in weathering and oceanic carbon reservoirs. The study also examines millennial-scale climate variations, showing three well-defined relative maxima in CO₂, temperature, and methane levels during MIS 18, which are consistent with Antarctic Isotope Maximum (AIM) events. These events are linked to the bipolar seesaw mechanism, with oceanic and terrestrial processes contributing to CO₂ variations. The findings provide strong evidence for active climate dynamics during MIS 18, highlighting the complex interactions between the carbon cycle and climate. The methods used for CO₂ measurements are based on dry extraction techniques followed by laser absorption spectroscopy and gas chromatography, ensuring accurate and reliable data. The study contributes to a better understanding of past climate variability and the natural range of atmospheric CO₂ concentrations.A high-resolution record of atmospheric carbon dioxide (CO₂) concentrations from 650,000 to 800,000 years before present (BP) has been obtained from the EPICA Dome C ice core in Antarctica. This record extends the previously known CO₂ levels by two complete glacial cycles, providing a more comprehensive understanding of past atmospheric CO₂ levels. The data show a strong correlation between CO₂ concentrations and Antarctic temperatures over eight glacial cycles, but with significantly lower concentrations between 650,000 and 750,000 years BP. The lowest CO₂ concentration measured in an ice core, 172 p.p.m.v., was found during Marine Isotope Stage (MIS) 16, reflecting enhanced oceanic carbon storage. The record also reveals a natural range of CO₂ concentrations from about 170 to 300 p.p.m.v. during the late Quaternary, with a gradual increase of about 8 p.p.m.v. per thousand years to 190 p.p.m.v. at 665 kyr BP. The study involved two deep ice cores drilled in Antarctica, with measurements conducted using various techniques, including laser absorption spectroscopy and gas chromatography. The data show a consistent record of CO₂ levels, with some variations due to measurement artifacts. The record also highlights significant fluctuations in CO₂ levels during different glacial and interglacial periods, with a notable shift in the CO₂/temperature relationship after MIS 16. This shift is not explained by temperature overestimation but may indicate a long-term increase in CO₂ levels from 800 to 400 kyr BP, influenced by changes in weathering and oceanic carbon reservoirs. The study also examines millennial-scale climate variations, showing three well-defined relative maxima in CO₂, temperature, and methane levels during MIS 18, which are consistent with Antarctic Isotope Maximum (AIM) events. These events are linked to the bipolar seesaw mechanism, with oceanic and terrestrial processes contributing to CO₂ variations. The findings provide strong evidence for active climate dynamics during MIS 18, highlighting the complex interactions between the carbon cycle and climate. The methods used for CO₂ measurements are based on dry extraction techniques followed by laser absorption spectroscopy and gas chromatography, ensuring accurate and reliable data. The study contributes to a better understanding of past climate variability and the natural range of atmospheric CO₂ concentrations.