the concentration of carbon dioxide in earth’s atmosphere has climbed to a level last seen more than 3 million years ago — before humans even appeared on the rocky ball we call home.
the concentration of carbon dioxide in earth’s atmosphere has climbed to a level last seen more than 3 million years ago — before humans even appeared on the rocky ball we call home.
carbon dioxide in earth's atmosphere:24
carbon dioxide in earth's atmosphere
the current concentration may be the highest in the last 20 million years.