Earth’s future unfolds across timescales that range from decades to billions of years, and the planet will transform dramatically at every stage. In the near term, climate change driven by human activity is already reshaping coastlines, ecosystems, and weather patterns. Over millions of years, the continents will rearrange themselves into a new supercontinent. And billions of years from now, the Sun itself will expand and almost certainly consume the planet entirely. Here’s what science tells us about each chapter.
The Next Century: A Warmer, Higher-Sea World
How much Earth warms by 2100 depends almost entirely on how much carbon humanity keeps pumping into the atmosphere. Under the most optimistic scenario, where emissions drop sharply, global temperatures will rise 1.0°C to 1.8°C above pre-industrial levels. Under the worst-case scenario, with fossil fuel use continuing to accelerate, that range jumps to 3.3°C to 5.7°C. The middle-of-the-road path, which roughly tracks current policies, lands between 2.1°C and 3.5°C.
Sea levels follow temperature upward. Even in the best case, oceans are projected to rise about 0.38 meters (roughly 15 inches) by 2100. In the worst case, the rise reaches 0.77 meters (about 2.5 feet), with a low-confidence upper bound of 1.6 meters (over 5 feet) if ice sheet instabilities kick in faster than expected. That may sound modest, but a half-meter of sea level rise is enough to permanently flood large sections of coastal cities, displace hundreds of millions of people, and contaminate freshwater supplies with saltwater.
The Sixth Mass Extinction Is Already Underway
Species are currently going extinct at roughly 1,000 times the natural background rate. That background rate, the normal pace at which species disappear without any human influence, is about one extinction per ten million species per year. Future extinction rates could climb to 10,000 times higher than that baseline as habitat destruction, climate change, pollution, and invasive species compound one another.
This is not a hypothetical crisis waiting in the distance. Coral reefs, rainforests, and polar ecosystems are already collapsing. The trajectory Earth is on now mirrors the early stages of the five previous mass extinctions in the fossil record, events that each wiped out 60% to 96% of all species. The difference this time is speed: changes that previously took tens of thousands of years are happening within decades.
Ice Ages Postponed by Carbon Emissions
Without human interference, Earth’s climate follows predictable cycles driven by slow wobbles in its orbit around the Sun. These cycles have triggered ice ages roughly every 100,000 years for the past million years. Based on this pattern, the next glacial period would naturally begin about 10,000 years from now.
That timeline is now effectively off the table. The carbon dioxide humans have already added to the atmosphere has diverted the climate from its natural course. Researchers at UC Santa Barbara and University College London confirmed that the orbital pattern still holds, but the sheer volume of greenhouse gases means a return to glacial conditions in 10,000 years is “very unlikely.” In a strange twist, humanity may have accidentally prevented the next ice age while creating a different, potentially more dangerous climate problem.
The Moon Is Slowly Drifting Away
The Moon is receding from Earth at a rate of about 3.83 centimeters per year, roughly the speed your fingernails grow. This happens because tidal interactions gradually transfer energy from Earth’s rotation to the Moon’s orbit. As the Moon moves farther away, Earth’s rotation slows down, and days get longer by about 1 to 2 milliseconds per century.
Over hundreds of millions of years, this adds up. Days were only about 22 hours long during the age of the dinosaurs. Far into the future, days could stretch well beyond 24 hours, and the Moon will appear smaller in the sky. Eventually, the Moon will be too far away to produce total solar eclipses, a change already creeping closer with each passing year. The Moon’s retreat also weakens its stabilizing effect on Earth’s axial tilt, which could eventually make the planet’s seasons more extreme and erratic.
A New Supercontinent in 250 Million Years
Earth’s continents are still moving, driven by the same tectonic forces that assembled and broke apart every previous supercontinent. Models suggest the continents will merge again in roughly 200 to 250 million years. Scientists have proposed several configurations. In one, called “Amasia,” all continents except Antarctica converge around the North Pole. In another, called “Aurica,” they cluster near the equator. The exact arrangement matters enormously for climate: a polar supercontinent would trap ice at one end of the landmass, while an equatorial one could turn the interior into an uninhabitable desert.
A 2023 study found that the formation of a future supercontinent would likely make Earth inhospitable to land-based mammals, triggering a mass extinction. The combination of intense volcanism from colliding plates, a more active Sun putting out more energy, and a massive continental interior far from any ocean’s moderating influence would push temperatures beyond what most complex land animals can survive.
The Slow Death of Plant Life
Paradoxically, while too much CO₂ is the problem right now, too little CO₂ will be the problem in the very long run. The Sun is gradually getting brighter, about 1% more luminous every 100 million years. As it does, Earth’s natural thermostat responds by pulling more carbon dioxide out of the atmosphere through chemical weathering of rocks. Eventually, CO₂ levels will drop below the threshold plants need to survive.
Plants that use the most common form of photosynthesis (called C3, which includes trees, rice, and wheat) need at least 150 parts per million of CO₂. Models estimate that threshold will be crossed in about 100 million years, killing off the majority of plant species. Grasses and certain crops that use a more efficient form of photosynthesis (C4) can survive on CO₂ levels as low as 10 parts per million, buying them another billion years or so. But once even those plants die, the oxygen they produce disappears with them, and animal life on land becomes impossible.
The Sun Will Likely Swallow Earth
About 5 billion years from now, the Sun will exhaust the hydrogen fuel in its core and begin expanding into a red giant, swelling to hundreds of times its current size. As it grows, it will lose mass, and that mass loss will cause Earth’s orbit to expand outward. For a time, scientists debated whether this orbital expansion might save the planet by pushing it beyond the Sun’s expanding edge.
The current consensus, published in the journal Astronomy & Astrophysics, is that it won’t. Even accounting for Earth’s outward migration, tidal forces between the bloated Sun and the planet will drag Earth inward. The planet will most likely be engulfed near the tip of the Sun’s red giant phase. The researchers note that the exact outcome is technically “stochastic,” meaning it depends on variables that can’t be precisely predicted this far in advance, but the most probable result is the same: Earth gets consumed. If it somehow survives, it would orbit a small, dim white dwarf star in a moderately stretched orbit, a charred husk of its former self.
Asteroid Impacts: Rare but Real
Somewhere between now and Earth’s fiery end, asteroid impacts remain a wildcard. Objects large enough to threaten civilization, those wider than one to two kilometers, strike only once every few million years. Smaller asteroids hit more frequently but cause only localized damage. Rocks under about 25 meters burn up in the atmosphere entirely.
NASA’s Planetary Defense Coordination Office tracks all potentially hazardous objects, defined as asteroids or comets that come within 5 million miles of Earth and are large enough to reach the surface. No known asteroid currently poses a near-term threat to the planet. And unlike every other item on this list, asteroid impacts are the one future catastrophe humanity might actually be able to prevent: NASA’s DART mission in 2022 successfully altered an asteroid’s orbit, proving the concept of planetary defense works in practice.