Future of Earth

A dark gray and red sphere representing the Earth lies against a black background to the right of an orange circular object representing the Sun
Conjectured illustration of the scorched Earth after the Sun has entered the red giant phase, about 5–7 billion years from now[1]
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The biological and geological future of Earth can be extrapolated based on the estimated effects of several long-term influences. These include the chemistry at Earth's surface, the cooling rate of the planet's interior, the gravitational interactions with other objects in the Solar System, and a steady increase in the Sun's luminosity. An uncertain factor is the pervasive influence of technology introduced by humans, such as climate engineering,[2] which could cause significant changes to the planet.[3][4] For example, the current Holocene extinction[5] is being caused by technology,[6] and the effects may last for up to five million years.[7] In turn, technology may result in the extinction of humanity, leaving the planet to gradually return to a slower evolutionary pace resulting solely from long-term natural processes.[8][9]

Over time intervals of hundreds of millions of years, random celestial events pose a global risk to the biosphere, which can result in mass extinctions. These include impacts by comets or asteroids and the possibility of a near-Earth supernova—a massive stellar explosion within a 100-light-year (31-parsec) radius of the Sun. Other large-scale geological events are more predictable. Milankovitch's theory predicts that the planet will continue to undergo glacial periods at least until the Quaternary glaciation comes to an end. These periods are caused by the variations in eccentricity, axial tilt, and precession of Earth's orbit.[10] As part of the ongoing supercontinent cycle, plate tectonics will probably result in a supercontinent in 250–350 million years. Sometime in the next 1.5–4.5 billion years, Earth's axial tilt may begin to undergo chaotic variations, with changes in the axial tilt of up to 90°.[11]

The luminosity of the Sun will steadily increase, causing a rise in the solar radiation reaching Earth and resulting in a higher rate of weathering of silicate minerals. This will affect the carbonate–silicate cycle, which will cause a decrease in the level of carbon dioxide in the atmosphere. In about 600 million years from now, the level of carbon dioxide will fall below the level needed to sustain C3 carbon fixation photosynthesis used by trees. Some plants use the C4 carbon fixation method to persist at carbon dioxide concentrations as low as ten parts per million. However, the long-term trend is for plant life to die off altogether. The extinction of plants will be the demise of almost all animal life since plants are the base of much of the animal food chain on Earth.[12][13]

In about one billion years the solar luminosity will be 10% higher, causing the atmosphere to become a "moist greenhouse", resulting in a runaway evaporation of the oceans. As a likely consequence, plate tectonics and the entire carbon cycle will end.[14] Following this event, in about 2–3 billion years, the planet's magnetic dynamo may cease, causing the magnetosphere to decay and leading to an accelerated loss of volatiles from the outer atmosphere. Four billion years from now, the increase in Earth's surface temperature will cause a runaway greenhouse effect, creating conditions more extreme than present-day Venus and heating Earth's surface enough to melt it. By that point, all life on Earth will be extinct.[15][16] Finally, the most probable fate of the planet is absorption by the Sun in about 7.5 billion years, after the star has entered the red giant phase and expanded beyond the planet's current orbit.[17]

  1. ^ Cite error: The named reference apj418 was invoked but never defined (see the help page).
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  3. ^ Cite error: The named reference Mooney was invoked but never defined (see the help page).
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  6. ^ Myers 2000, pp. 63–70.
  7. ^ Reaka-Kudla, Wilson & Wilson 1997, pp. 132–33.
  8. ^ Cite error: The named reference bostrom2002 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference geo2_3_113 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference cc79 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference aaa318 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference mj2012 was invoked but never defined (see the help page).
  13. ^ Ward & Brownlee 2003, pp. 117–28.
  14. ^ Cite error: The named reference lunine09 was invoked but never defined (see the help page).
  15. ^ Ward & Brownlee 2003, p. 142.
  16. ^ Fishbaugh et al. 2007, p. 114.
  17. ^ Cite error: The named reference mnras361 was invoked but never defined (see the help page).