The Sun is gradually getting brighter, and someday this will make Earth uninhabitable for plants—either due to overheating or lack of carbon dioxide. Previous estimates gave the biosphere about a billion more years, but a recent study extended that to 1.6–1.86 billion years by more accurately accounting for rock weathering (the process that binds CO₂). The new model includes seafloor weathering and random fluctuations in CO₂ emissions from the Earth's interior. It turned out that if seafloor weathering plays a major role, the timeline could shrink, but it would still be over a billion years. It's like a race between two 'chemical pumps'—continental and oceanic—and the fate of green life hangs in their balance.
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.
🎯 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.