Scientists from Toho University in Japan and the Georgia Institute of Technology in the United States ran 400,000 computer simulations to predict when Earth will lose its breathable atmosphere. They discovered that complex life—encompassing animals, plants, and humans—will disappear in approximately one billion years, reducing the previous estimate of two billion years by roughly half.
The research team, led by Kazumi Ozaki and Christopher Reinhard, found that Earth’s oxygen-rich atmosphere will last only about 1.08 billion years (with a margin of error of 140 million years). After that time, the planet will transition to a state where only hardy microbes can survive in extreme environments.
This discovery represents a significant refinement of earlier estimates, as scientists now possess better climate models, a deeper understanding of how stars evolve, and more detailed knowledge of Earth’s biogeochemical cycles than they did decades ago.
How Earth Will Lose Its Atmosphere
As the Sun ages, it gradually increases in brightness—growing brighter by about one percent every 100 million years. This seemingly small increase creates a devastating domino effect over millions of years. Warmer temperatures cause more water to evaporate from the oceans, and water vapor traps heat like a powerful greenhouse gas, creating more warming and evaporation in a self-reinforcing cycle.
Meanwhile, ultraviolet radiation from the brightening Sun breaks down carbon dioxide in the atmosphere, and as CO₂ levels drop, plants cannot photosynthesize effectively. Without enough plants producing oxygen on land, and with warming oceans disrupting algae and other water plants, the planet’s oxygen supply plummets.
The simulations show that when this process reaches a critical tipping point, oxygen levels do not decline gradually; instead, they crash from today’s 21 percent to around one percent in as little as 10,000 to 100,000 years —an almost instantaneous event in geological terms. Scientists refer to this catastrophic event as “rapid deoxygenation.”
The Extinction Timeline and What It Means
Complex life will not disappear all at once but rather in waves spanning billions of years. In roughly 100 million years, C₃ plants will begin failing because CO₂ levels fall too low for them to survive. Large animals will struggle to cope with rising heat and humidity over hundreds of millions of years, gradually disappearing as the climate becomes uninhabitable for multicellular organisms.
The models predict that eukaryotes will vanish around 1.3 billion years from now. Even after surface conditions become lethal, microbes will retreat deep underground into the Earth’s crust, known as the “deep biosphere,” where they may persist for several hundred million years, potentially until 2.8 billion years from now.
These findings echo Venus’s fate: Venus likely experienced a runaway greenhouse effect between 250 million and three billion years ago, transforming from a potentially habitable world with liquid water into a hellscape with surface temperatures around 475 degrees Celsius and an atmosphere 92 times thicker than Earth’s.
The research suggests that Earth-like planets maintain oxygen-rich atmospheres suitable for complex life for only a billion years meaning the odds of finding other oxygen-rich worlds are lower than scientists previously thought. However, scientists emphasize that understanding these billion-year timescales helps us recognize how sensitive Earth’s climate actually is to small changes in energy balance and atmospheric composition.
Human-driven greenhouse gas emissions are pushing temperatures upward on timescales of decades and centuries, not millions of years. While humanity cannot stop the Sun from eventually brightening, our choices today determine whether Earth remains livable for human civilization in the near term—a window far more relevant to society than the distant future.
Sources:
Nature Geoscience (2021)
EurekAlert, March 1, 2021
ArXiv 2103.02694
Ozaki & Reinhard
Carl Sagan & Michael Hart’s historical work
Science journalism outlets (2025)