Risks to civilization, humans, and planet Earth are existential risks that could threaten humankind as a whole, have adverse consequences for the course of human civilization, or even cause the end of planet Earth. The concept is expressed in various phrases such as "End of the World", "Doomsday", "Ragnarök", "Judgment Day", "Armageddon", "the Apocalypse", "Yawm al-Qiyāmah" and others.
Future scenarios
Many scenarios have been suggested. Some that will almost certainly end life on Earth are certain to occur, but on a very long timescale. Others are likely to happen on a shorter timescale, but will probably not completely destroy civilization. Still others are extremely unlikely, and may even be impossible. For example, Nick Bostrom writes:
Some foreseen hazards (hence not members of the current category) which have been excluded from the list on grounds that they seem too unlikely to cause a global terminal disaster are: solar flares, supernovae, black hole explosions or mergers, gamma-ray bursts, galactic center outbursts, buildup of air pollution, gradual loss of human fertility, and various religious doomsday scenarios.
Distant future
There are a number of cosmological theories as to the universe's ultimate fate that exclude the indefinite continuation of life. Most involve time periods and distant futures much greater than the current 13.7-billion-year age of the universe. A long-established and widely accepted theory is the eventual heat death of the universe.
Calculations indicate that the Andromeda Galaxy is on a collision course with the Milky Way. Andromeda is approaching at an average speed of about 140 kilometres (87 miles) per second and thus impact is predicted in about 3 billion years. This merging could eject the solar system in a more eccentric orbit and an unwanted position in the merged galaxy causing our planet to become uninhabitable, even if an actual collision does not take place.
The theory of stellar evolution predicts that our Sun will exhaust its hydrogen core and become a red giant in about 5 billion years, becoming thousands of times more luminous and losing roughly 30% of its current mass. Ignoring tidal effects, the Earth would then orbit 1.7 AU (250,000,000 km) from the Sun at its maximum radius. This would allow the Earth to escape being enveloped by the Sun's now expanded and thin outer atmosphere, though most life, if not all, would perish due to the Sun's proximity. However, a more recent study suggests that the Earth's orbit will decay due to the effects of tidal drag, causing it to enter the Sun's expanded atmosphere and be destroyed in 7.6 billion years. Before being swallowed by the Sun, the Earth's oceans would evaporate, and the Earth would finally be destroyed by tidal forces.
Meteorite impact
Earth has collided with several large asteroids in recent geological history. The Cretaceous-Tertiary asteroid, for example, is theorized to have caused the extinction of the dinosaurs 65 million years ago. If such an object struck Earth it could have a serious impact on civilization. It is even possible that humanity would be completely destroyed; for this to occur the asteroid would need to be at least 1 km (0.62 miles) in diameter, but probably between 3 and 10 km (2–6 miles). Asteroids with a 1 km diameter have impacted the Earth on average once every 500,000 years. Larger asteroids are less common. So-called Near-Earth asteroids are regularly being observed.
1.4 million years from now the star Gliese 710 is expected to cause an increase in the number of meteoroids in the vicinity of Earth by passing within 1.1 light years of the Sun. Some models predict that this will cause a large number of comets from the Oort cloud to impact Earth, whereas other models predict only a 5% increase in the rate of impact.
Other cosmic threats
A number of other scenarios have been suggested. Massive objects, e.g., a star, large planet or black hole, could be catastrophic if a close encounter occurred in the solar system. (Gravity from the wandering objects might disrupt orbits and/or fling bodies into other objects, thus resulting in meteorite impacts or climate change. Also, heat from the wandering objects might cause extinctions; tidal forces could cause erosion along our coastlines.)
Another threat might come from gamma ray bursts. Both are very unlikely. Still others see extraterrestrial life as a possible threat to humankind; although alien life has never been found, scientists such as Carl Sagan have postulated that the existence of extraterrestrial life is very likely. In 1969, the "Extra-Terrestrial Exposure Law" was added to the Code of Federal Regulations (Title 14, Section 1211) in response to the possibility of biological contamination resulting from the US Apollo Space Program. It was removed in 1991. Scientists consider such a scenario technically possible, but unlikely.
In April 2008, it was announced that two simulations of long-term planetary movement, one at Paris Observatory and the other at University of California, Santa Cruz indicate a 1% chance that Mercury's orbit could be made unstable by Jupiter's gravitational pull sometime during the lifespan of the sun. Were this to happen, the simulations suggest a collision with Earth could be one of four possible outcomes (the others being Mercury colliding with the Sun, colliding with Venus, or being ejected from the solar system altogether). If Mercury were to collide with the Earth, all life on Earth would be obliterated and the impact might displace enough matter into orbit to form another moon. Note that an asteroid just 15 km wide is said to have destroyed the dinosaurs; Mercury is some 5,000 km in diameter.
Earth
Global pandemic
A less predictable scenario is a global pandemic. For example, if HIV were to mutate and become as transmissible as the common cold, the consequences would be disastrous. It has been hypothesised that such an extremely virulent pathogen might not evolve. This is because a pathogen that quickly kills its hosts might not have enough time to spread to new ones, while one that kills its hosts more slowly or not at all will allow carriers more time to spread the infection, and thus likely out-compete a more lethal species or strain.This simple model predicts that if virulence and transmission are not linked in any way, pathogens will evolve towards low virulence and rapid transmission. However, this assumption is not always valid and in more complex models, where the level of virulence and the rate of transmission are related, high levels of virulence can evolve.
The level of virulence that is possible is instead limited by the existence of complex populations of hosts, with different susceptibilities to infection, or by some hosts being geographically-isolated.The size of the host population and competition between different strains of pathogens can also alter virulence. Interestingly, a pathogen that only infects humans as a secondary host and usually infects another species (a zoonosis) may have little constraint on its virulence in people, since infection here is an accidental event and its evolution is driven by events in another species.
Megatsunami
Another possibility is a megatsunami. A megatsunami could, for example, destroy the entire East Coast of the United States. The coastal areas of the entire world could also be flooded in case of the collapse of the West Antarctic Ice Sheet. While none of these scenarios are likely to destroy humanity completely, they could regionally threaten civilization. There have been two recent high-fatality tsunamis--after the 2011 Tōhoku earthquake and the 2004 Indian Ocean earthquake, although they were not large enough to be considered megatsunamis. A megatsunami could have astronomical origins as well, such as an asteroid impact in an ocean.
Climate change and global warming
Climate change is any long-term significant change in the expected patterns of average weather of a specific region (or, more relevantly to contemporary socio-political concerns, of the Earth as a whole) over an appropriately significant period of time. Climate change reflects abnormal variations to the expected climate within the Earth's atmosphere and subsequent effects on other parts of the Earth, such as in the ice caps over durations ranging from decades to millions of years. According to the UN’s Office for the Coordination of Humanitarian Affairs (OCHA), climate disasters are on the rise. Around 70 percent of disasters are now climate related – up from around 50 percent from two decades ago.
These disasters take a heavier human toll and come with a higher price tag.In the last decade, 2.4 billion people were affected by climate related disasters, compared to 1.7 billion in the previous decade and the cost of responding to disasters has risen tenfold between 1992 and 2008. Destructive sudden heavy rains, intense tropical storms, repeated flooding and droughts are likely to increase, as will the vulnerability of local communities in the absence of strong concerted action. Sea level rise may completely inundate certain areas.
Ice age
In the history of the Earth, twelve ice ages have occurred. More ice ages will be possible at an interval of 40,000–100,000 years although engineers working for Posiva, a Finnish company involved in the underground storage of nuclear waste, have built their facility to withstand an Ice Age starting as 'soon' as 20,000 years. An Ice Age would have a serious impact on civilization because vast areas of land (mainly in North America, Europe, and Asia) could become uninhabitable. It would still be possible to live in the tropical regions, but with possible loss of humidity/water. Currently, the world is existing in an interglacial period within a much older glacial event. The last glacial expansion ended about 10,000 years ago, and all civilizations evolved later.
Ecological disaster
An ecological disaster, such as world crop failure and collapse of ecosystem services, could be induced by the present trends of overpopulation, economic development, and non-sustainable agriculture. Most of these scenarios involve one or more of the following: Holocene extinction event, scarcity of water that could lead to approximately one half of the Earth's population being without safe drinking water, pollinator decline, overfishing, massive deforestation, desertification, climate change, or massive water pollution episodes. A very recent threat in this direction is colony collapse disorder, a phenomenon that might foreshadow the imminent extinction of the Western honeybee. As the bee plays a vital role in pollination, its extinction would severely disrupt the food chain.
World population and agricultural crisis
The 20th century saw a rapid increase in human population due to medical developments and massive increase in agricultural productivity made by the Green Revolution. Between 1950 and 1984, as the Green Revolution transformed agriculture around the globe, world grain production increased by 250%. The Green Revolution in agriculture helped food production to keep pace with worldwide population growth or actually enabled population growth. The energy for the Green Revolution was provided by fossil fuels in the form of fertilizers (natural gas), pesticides (oil), and hydrocarbon fueled irrigation. David Pimentel, professor of ecology and agriculture at Cornell University, and Mario Giampietro, senior researcher at the National Research Institute on Food and Nutrition (INRAN), place in their study Food, Land, Population and the U.S. Economy the maximum U.S. population for a sustainable economy at 200 million. To achieve a sustainable economy and avert disaster, the United States must reduce its population by at least one-third, and world population will have to be reduced by two-thirds, says the study.
The authors of this study believe that the mentioned agricultural crisis will only begin to impact us after 2020, and will not become critical until 2050. Geologist Dale Allen Pfeiffer claims that coming decades could see spiraling food prices without relief and massive starvation on a global level such as never experienced before.
Wheat is humanity's 3rd most produced cereal. Extant fungal infections such as Ug99 (a kind of stem rust) can cause 100% crop losses in most modern varieties. Little or no treatment is possible and infection spreads on the wind. Should the world's large grain producing areas become infected then there would be a crisis in wheat availability leading to price spikes and shortages in other food stuffs.
Supervolcano
When the supervolcano at Yellowstone last erupted 640,000 years ago, the magma and ash ejected from the caldera covered most of the United States west of the Mississippi river and part of northeastern Mexico. Another such eruption could threaten civilization. Such an eruption could also release large amounts of gases that could alter the balance of the planet's carbon dioxide and cause a runaway greenhouse effect, or enough pyroclastic debris and other material might be thrown into the atmosphere to partially block out the sun and cause a volcanic winter, as happened in 1816 following the eruption of Mount Tambora, the so-called Year Without a Summer. Such an eruption might cause the immediate deaths of millions of people several hundred miles from the eruption, and perhaps billions of deaths worldwide due to the failure of the monsoon, as well as destruction of the "American breadbasket", causing starvation on a massive scale. Supervolcanoes are more likely threats than many others, as a prehistoric Indonesian supervolcano eruption may have reduced the human population to only a few thousand individuals, while no catastrophic bolide impact, for example, has occurred since long before modern humans evolved.
Artificial intelligence
It has been suggested that learning computers that rapidly become superintelligent may take unforeseen actions or that robots would out-compete humanity. Because of its exceptional scheduling and organizational capability and the range of novel technologies it could develop, it is possible that the first Earth superintelligence to emerge could rapidly become matchless and unrivaled: conceivably it would be able to bring about almost any possible outcome, and be able to foil virtually any attempt that threatened to prevent it achieving its desires. It could eliminate, wiping out if it chose, any other challenging rival intellects; alternatively it might manipulate or persuade them to change their behavior towards its own interests, or it may merely obstruct their attempts at interference.
Vernor Vinge has suggested that a moment may come when computers and robots are smarter than humans. He calls this "the Singularity." He suggests that it may be somewhat or possibly very dangerous for humans.This is discussed by a philosophy called Singularitarianism.
In 2009, experts attended a conference hosted by the Association for the Advancement of Artificial Intelligence (AAAI) to discuss whether computers and robots might be able to acquire any sort of autonomy, and how much these abilities might pose a threat or hazard. They noted that some robots have acquired various forms of semi-autonomy, including being able to find power sources on their own and being able to independently choose targets to attack with weapons. They also noted that some computer viruses can evade elimination and have achieved "cockroach intelligence." They noted that self-awareness as depicted in science-fiction is probably unlikely, but that there were other potential hazards and pitfalls.Various media sources and scientific groups have noted separate trends in differing areas which might together result in greater robotic functionalities and autonomy, and which pose some inherent concerns.
Some experts and academics have questioned the use of robots for military combat, especially when such robots are given some degree of autonomous functions. There are also concerns about technology which might allow some armed robots to be controlled mainly by other robots. The US Navy has funded a report which indicates that as military robots become more complex, there should be greater attention to implications of their ability to make autonomous decisions. One researcher states that autonomous robots might be more humane, as they could make decisions more effectively. However, other experts question this.
Biotechnology could lead to the creation of a pandemic, Nanotechnology could lead to grey goo in which out-of-control self-replicating robots consume all living matter on Earth while building more of themselves - in both cases, either deliberately or by accident. It has also been suggested that physical scientists might accidentally create a device that could destroy the earth and the solar system.
Climate change and ecology
It has been suggested that runaway global warming might cause the climate on Earth to become like Venus, which would make it uninhabitable. In less extreme scenarios it could cause the end of civilization, as we know it.According to a UN climate report, the Himalayan glaciers that are the sources of Asia's biggest rivers - Ganges, Indus, Brahmaputra, Yangtze, Mekong, Salween and Yellow - could disappear by 2350 as temperatures rise, although an initial announcement of that report erroneously stated the date as 2035.Approximately 3 billion people live in the drainage basin of the Himalayan rivers, which is almost half of the current human population (see Environmental migrant.
The Himalayan system, which includes outlying subranges, stretches across: Afghanistan, Bangladesh, Bhutan, People's Republic of China, India, Nepal, Burma, Cambodia, Thailand, Laos, Vietnam, Malaysia and Pakistan. Some of the world's major rivers, Ganges, Indus, Brahmaputra, Yangtze, Mekong, Salween and Yellow River, rise in the Himalayas, and their combined drainage basin in India, China, Pakistan, Bangladesh, Nepal and Myanmar could experience floods followed by droughts in coming decades. In India alone, the Ganges provides water for drinking and farming for more than 500 million people. The west coast of North America, which gets much of its water from glaciers in mountain ranges such as the Rocky Mountains, Cascade Mountains and Sierra Nevada, also would be affected.
According to the California Department of Water Resources, if more water supplies are not found by 2020, California residents will face a water shortfall nearly as great as the amount consumed today.
Directly linked to observed increases in the intensity and frequency of natural disasters, global warming and climate change are now considered key drivers behind rising global humanitarian and emergency relief needs. According to the UN’s Office for the Coordination of Humanitarian Affairs (OCHA), climate disasters are on the rise. Around 70 percent of disasters are now climate related – up from around 50 percent from two decades ago. These disasters take a heavier human toll and come with a higher price tag. In the last decade, 2.4 billion people were affected by climate related disasters, compared to 1.7 billion in the previous decade and the cost of responding to disasters has risen tenfold between 1992 and 2008.Destructive sudden heavy rains, intense tropical storms, repeated flooding and droughts are likely to increase, as will the vulnerability of local communities in the absence of strong concerted action.
Approximately 40% of the world's agricultural land is seriously degraded. In Africa, if current trends of soil degradation continue, the continent might be able to feed just 25% of its population by 2025, according to UNU's Ghana-based Institute for Natural Resources in Africa.
James Lovelock, creator of the Gaia hypothesis, in his book The Revenge of Gaia (2006), has suggested that the elimination of rain forests, and the falling planetary biodiversity is removing the homeostatic negative feedback mechanisms that maintain climate stability by reducing the effects of greenhouse gas emissions (particularly carbon dioxide). With the heating of the oceans, the extension of the thermocline layer into Arctic and Antarctic waters is preventing the overturning and nutrient enrichment necessary for algal blooms of phytoplankton on which the ecosystems of these areas depend. With the loss of phytoplankton and tropical rain forests, two of the main carbon dioxide sinks for reducing global warming, he suggests a runaway positive feedback effect could cause tropical deserts to cover most of the world's tropical regions, and the disappearance of polar ice caps, posing a serious challenge to global civilization.
Using scenario analysis, the Global Scenario Group (GSG), a coalition of international scientists convened by Paul Raskin, developed a series of possible futures for the world as it enters a Planetary Phase of Civilization. One scenario involves the complete breakdown of civilization as the effects of climate change become more pronounced, competition for scarce resources increases, and the rift between the poor and the wealthy widens. The GSG’s other scenarios, such as Policy Reform, Eco-Communalism, and Great Transition avoid this societal collapse and eventually result in environmental and social sustainability. They claim the outcome is dependent on human choice and the possible formation of a global citizens movement which could influence the trajectory of global development.
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