The Sun is slowly brightening, and in hundreds of millions of years its heat would become lethal for Earth. Fortunately, the built-in planetary thermostat — the carbon cycle — when overheating triggers rocks to absorb carbon dioxide faster, cooling the climate. The price of cooling is that plants lose their main source of food.
Scientists have recalculated the thermostat's operation, adding the effect of seafloor weathering (water eats away rocks, taking up CO₂) and random volcanic emissions. Results: even with aggressive gas sequestering by the ocean floor, greenery will persist for over a billion years. In a quiet scenario — 1.6–1.86 billion years, longer than previous estimates.
These numbers change our idea of the biosphere's shelf life and help search for life around other stars. The planetary thermostat can work on exoplanets with oceans and volcanoes, making them habitable for longer than thought.
as written by the authors arXiv:2512.24538
Current understanding suggests that as the Sun brightens in the far future, Earth's carbonate-silicate cycle will offset increasing temperatures by drawing CO$$_2$$ out of the atmosphere, ultimately leading to the extinction of all terrestrial plant life via either overheating or CO$$_2$$ starvation. Most previous estimates put the future lifespan of Earth's terrestrial biosphere at $$\sim$$1 billion yr, but recent work used a new coupled climate-continental weathering model with up-to-date parameter constraints to revise this estimate upward to 1.6-1.86 billion yr. In this study, we extend the model to examine the impacts of seafloor weathering and stochastic variations in CO$$_2$$ outgassing rates on the remaining lifespan of Earth's terrestrial biosphere. We find that if seafloor weathering has a stronger feedback than continental weathering and accounts for a large portion of global silicate weathering, then the remaining lifespan of the terrestrial biosphere can be shortened, but a lifespan of more than 1 billion yr (Gyr) remains likely. Similarly, stochastic fluctuations in outgassing rates can have a significant impact if the size of the fluctuations exceed those observed over the last 1 billion yr. The impact of weak seafloor weathering and lower variability stochasticity are minor. Our work provisionally supports a lengthened lifespan of Earth's terrestrial biosphere, suggests robustness of this lengthened lifespan to planetary parameters that may vary among exoplanets, and identifies seafloor weathering as a key process that requires further study and constraint.
The process of rock weathering that regulates climate was discovered only in the 20th century, though it has been operating for billions of years.
In Asimov's 'Foundation', scientists predicted the fall of civilization centuries ahead; here astronomers peer a billion years into the future of the biosphere.