Earth's Atmospheric Oxygen Levels Continue Long Slide

Atmospheric oxygen levels have declined over the past 1 million years, although not nearly enough to trigger any major problems for life on Earth, a new study finds. Atmospheric oxygen levels are fundamentally linked to the evolution of life on Earth, as well as changes in geochemical cycles related to climate variations. As such, scientists have long sought to reconstruct how atmospheric oxygen levels fluctuated in the past, and what might control these shifts.