Future of Earth

Scientists use current data to predict the biological and geological future of Earth. They look at several long-term influences to see how our planet might change. These influences include the chemistry of the surface and the cooling of the interior. They also study the Sun's increasing luminosity, which is its brightness. Gravitational interactions with other objects in the Solar System play a role too.

Understanding these processes helps us see how Earth will evolve over billions of years.

One major driver of change is the steady increase in solar luminosity. As the Sun gets brighter, more solar radiation reaches Earth. This extra energy increases the weathering of silicate minerals on the surface. This process affects the carbonate–silicate cycle, which regulates our atmosphere. Consequently, the level of carbon dioxide in the atmosphere will decrease. In about 600 million years, carbon dioxide levels will fall too low for C3 carbon fixation. This is the method of photosynthesis used by most trees.

While some plants use C4 carbon fixation to survive at ten parts per million, most plants will eventually die. This loss of plants would likely cause the demise of almost all animal life.

As time continues, the planet faces even more extreme shifts. In about one billion years, solar luminosity will be 10% higher. This will cause the atmosphere to become a "moist greenhouse." This state leads to the runaway evaporation of the oceans. Such an event would likely end plate tectonics and the entire carbon cycle.

Between 2 and 3 billion years from now, the planet's magnetic dynamo may cease. This is the process that creates our magnetic field. Without it, the magnetosphere may decay, causing a loss of volatiles from the outer atmosphere. Eventually, in about 4 billion years, a runaway greenhouse effect will make Earth more extreme than Venus. The surface will become hot enough to melt.

Geological processes also shape the planet's surface through plate tectonics. As part of the ongoing supercontinent cycle, plates will move and collide. This will likely create a new supercontinent in 250 to 350 million years.

Additionally, the Earth's axial tilt may undergo chaotic variations. This could involve changes of up to 90° within the next 1.5 to 4.5 billion years. While the orbit remains generally stable, these shifts can influence the planetary climate significantly. Predictable cycles, like Milankovitch cycles, also drive periodic glacial periods. These are caused by variations in eccentricity, axial tilt, and precession.

Human activity is currently a major influence on the biosphere. This era is known as the Holocene extinction. Humans have modified more than one-third of the land surface. We also use about 20% of global primary production. Since the 1950s, a biotic crisis has caused a large loss of species. By 2007, it was estimated that 10% of total species were lost.

At current rates, 30% of species may face extinction in the next century. This event could last for five million years and change how life evolves.

Celestial events pose additional risks to life on Earth. Impacts from comets or asteroids can cause mass extinctions. A major impact from an object 10 kilometers or larger can create a global disaster. Such an event creates a cloud of dust that blocks sunlight. This can lower land temperatures by 10°C within a week and halt photosynthesis for months.

There is also the risk of a near-Earth supernova. A supernova is a massive stellar explosion. An explosion within 32 light-years could deplete the ozone layer for centuries. This would increase UV-B radiation, which harms the phytoplankton at the base of the food chain.

Finally, the life of the Sun determines the ultimate fate of Earth. In about 7.5 billion years, the Sun will enter its red giant phase. During this stage, the star expands significantly. The Sun's expansion may cause it to absorb the Earth entirely. By this time, all life on Earth will have long been extinct. The planet's journey is one of constant, massive transformation driven by both internal and external forces.