Which percent of Earth’s atmosphere does carbon dioxide gas make up?

about 21 percent
about 21 percent

more than 99 percent
more than 99 percent

about 78 percent
about 78 percent

less than 1 percent

1 answer

Carbon dioxide (CO₂) makes up less than 1 percent of Earth's atmosphere. Specifically, it is approximately 0.04 percent, or around 400 parts per million, although this value can vary slightly over time due to natural processes and human activities.