How much carbon dioxide was there 4.5 billion years ago?

Approximately 4.5 billion years ago, during the Hadean eon, the Earth's atmosphere was primarily composed of volcanic gases, including a significant amount of carbon dioxide (CO2). Estimates suggest that CO2 levels could have been much higher than today, possibly making up 70-90% of the atmosphere. However, due to the lack of direct evidence from that time, these figures are largely based on geological and theoretical models rather than precise measurements.