When man first walked on the moon, the carbon dioxide concentration in Earth's atmosphere was 325 parts per million (ppm). By 9/11, it was 369 ppm, and when COVID-19 shut down normal life in 2020 ...

Scientists had thought that decreasing levels of carbon dioxide in the atmosphere caused a major change in the Earth's glacial cycle some time between 1.2 million and 500,000 years ago.