A global catastrophic risk is a hypothetical future event that has the potential to damage human well-being on a global scale.  Some events could cripple or destroy modern civilization . Any event That Could because human extinction or Permanently and DRASTICALLY curtail humanity’s potential is Known as an existential risk . 
Potential global catastrophic risks include anthropogenic risks and risks. Examples of technology are hostile artificial intelligence , biotechnology risks , or nanotechnology weapons . Insufficient global governance in the social and political field (potentially leading to a global war with or without a nuclear holocaust , bioterrorism using genetically modified organisms , cyberterrorism destroying critical infrastructures like the electrical grid, Or the failure to manage a natural pandemic ) as well as problems and Risks in the domain of earth system governance (with Risks resulting and from global warming , environmental degradation , Including extinction of species, or famine as a result of non-equitable resource distribution , human overpopulation , crop failures and non- sustainable agriculture ). Examples for non-anthropogenic risks are an asteroid impact event , a supervolcanic eruption , lethal gamma-ray burst , ageomagnetic storm destroying all electronic equipment, natural long-term climate change , extraterrestrial gold life impacting life on Earth.
Global catastrophic vs. existential
Philosopher Nick Bostrom’s classifications according to their scope and intensity.  A “global catastrophic risk” is any risk that is at least “global” in scope, and is not subjectively “imperceptible” in intensity. Those that are at least “trans-generational” in the scope and “terminal” [ clarification needed ]. While a global catastrophic risk may kill the vast majority of life on earth, man could still recover. An existential risk, on the other hand, is one that is destroys humanity (and, presumably,) entirely or at least any chance of civilization recovering. Bostrom considers existential risks to be far more significant. 
Similarly, in Catastrophe: Risk and Response , and Richard Posner singles out and groups together, and brings about “utter overthrow or ruin” on a global, rather than a “local or regional” scale. Posner singles out such events as they are worthy of special attention on cost-benefit grounds because they could directly or indirectly jeopardize the survival of the human race as a whole.  Posner’s events include meteor impacts , global warming runaway , gray goo , bioterrorism , and accelerator particle accidents .
Researchers experience difficulty in studying near human extinction directly,  While it is not possible that it will not be in the future, it does make modeling difficult, due to survivorship bias .
Bostrom identified four types of existential risk. “Bangs” are sudden disasters, which may be accidental or deliberate. He thinks the most likely sources of nanotechnology , nuclear war , and the possibility that the universe is a simulation that will end. “Crunches” are scenarios in which they survive, but civilization is irreversibly destroyed. The most likely causes of this, he believes, are exhaustion of natural resources , a stable global government that struggles with progress, or dysgenic pressuresthat lower average intelligence. “Shrieks” are undesirable future. For example, it could dominate human civilization. Bostrom believes that this scenario is most likely followed by a flawed superintelligence and a repressive totalitarian regime. “Whimpers” are the gradual decline of human civilization or current values. He thinks the most likely cause would be changing changing moral preference, followed by extraterrestrial invasion. 
Some risks, such as that of asteroid impact, with a one-in-a-million chance of causing humanity’s extinction in the next century,  have had their probabilities predicted with considerable precision. impacts could be much higher than originally calculated).  Similarly, the frequency of volcanic eruptions of the magnitude of catastrophic climate change, similar to the Toba Eruption , which may have caused the extinction of the human race,  has been estimated at about 1 in every 50,000 years. . The 2016 annual report by the Global Challenges Foundation estimates that an average is more likely to die during a human-extinction event than a car crash.  
The relative danger posed by other threats is much more difficult to calculate. In 2008, an annual survey of small but illustrious groups of experts on global catastrophic risks at the Global Catastrophic Risk Conference at the University of Oxford suggests a 19% chance of human extinction by the 2100 year. be taken “with a grain of salt”. 
Risk Estimated probability
for human extinction
Overall probability 19% Molecular nanotechnology weapons 5% Superintelligent AI 5% Non-nuclear wars 4% Engineered pandemic 2% Nuclear wars 1% Nanotechnology accident 0.5% Natural pandemic 0.05% Nuclear terrorism 0.03%
- Source table: Future of Humanity Institute , 2008. 
There are significant methodological challenges in estimating these risks with precision. Most attention has been given to the risks of civilization over the next 100 years, but forecasting for this length of time is difficult. The types of threats may be relatively constant, but new risks could be discovered. Anthropogenic threats, however, are likely to change dramatically with the development of new technology; while volcanoes have been a threat in the history of nuclear weapons. Historically, the ability of experts has been proven to be very limited. Man-made threats such as nuclear war or nanotechnologyare harder to predict than natural threats, due to the inherent methodological difficulties in the social sciences. In general, it is difficult to estimate the magnitude of the risk of this or other hazards, especially in the international relations and technology can change quickly.
Existential risks pose unique challenges to prediction, because of observation selection effects . Unexpectedly, the failure of a complete extinction event in the future is not possible, because of the fact that, existential risks in its history.  These anthropic issues can not be avoided because of these effects, as they are asteroidal impact craters on the Moon, or directly by the impact of new technology. 
Moral importance of existential risk
Some scholars have strongly favored reducing existential risk on the grounds that it greatly benefits future generations. Derek Parfit argues that extinction would be a great loss because our descendants could potentially survive for four billion years before the expansion of the Sun makes the Earth uninhabitable. Nick Bostrom argues that there is even greater potential in colonizing space. If future humans colonize space, they may be able to support a very large number of people on other planets, potentially lasting for trillions of years. Therefore, reducing existential risk by even a small amount would have a very significant impact on the expected number of people who will exist in the future.
Exponential discounting might make these future benefits much less significant. However, Gaverick Matheny has argued that such discounting is inappropriate when assessing the value of existential risk reduction.
Some economists have discussed the importance of global catastrophic risks, though not existential risks. Martin Weitzman argues that most of the expected economic damage from climate change may come from the small chance that warming greatly exceeds the mid-range expectations, resulting in catastrophic damage. Richard Posner has argued that we are doing far too little, in general, about small, hard-to-estimate risks of large-scale catastrophes.
Numerous cognitive biases can influence people’s judgment of the importance of existential risks, including scope insensitivity , hyperbolic discounting , heuristic availability , conjunction of fallacy , heuristic affect , and overconfidence effect . 
Scope insensitivity influences how bad people consider the extinction of the human race to be. For example, when people are motivated to donate money to altruistic causes, they are likely to increase the size of the issue. Similarly, people are often more concerned about threats to individuals than larger groups. 
There are economic reasons that can explain why so little effort is going into existential risk reduction. It is a global good, so it has a large nation decreases it, that nation will only enjoy a small fraction of the benefit of doing so. Moreover, the vast majority of the benefits may be enjoyed by the future generations, and perhaps these quadrillions of future people may be in a state of the art. 
Potential sources of risk
Some sources of natural disaster, such as meteor impacts or supervolcanos. Some of these have caused mass extinctions in the past.
On the other hand, some risks are man-made, such as global warming,  environmental degradation, engineered pandemics and nuclear war. According to the Future of the Humanity Institute , human extinction is more likely to result from anthropogenic causes than natural causes.  
In 2012, Cambridge University created the Cambridge Project for Existential Risk which examines threats to humankind caused by developing technologies.  The Center for the Study of Existential Risk is a multidisciplinary research center , dedicated to the scientific study and mitigation of the existential risks of this kind. 
The Cambridge Project states that the “greatest threats” to the human species are man-made; they are artificial intelligence, global warming, nuclear war, and rogue biotechnology. 
It has been suggested that learning to become superintelligent may take unforeseen actions or that robots would out-compete humanity (one-of-a-kind singularity scenario).  Because of its exceptional scheduling and organizational capabilities, it is possible that the first Earth would be better able to achieve a better outcome. , and be able to foil it. It could eliminate, wiping out if it thing, any other challenging rival intellects; alternatively it may manipulate or persuade them to change their behavior towards its own interests, or it may simply obstruct their attempts at interference.  In Bostrom’s book, Superintelligence: Paths, Dangers, Strategies , he defines this as the control problem. 
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 very dangerous for humans.  This is discussed by a philosophy called Singularitarianism .
Physicist Stephen Hawking , Microsoft founder Bill Gates and SpaceX founder Elon Musk -have Expressed Concerns about the possibility AI That Could evolve to the point That humans couldn’t control it, with Hawking Theorizing That this could “spell the end of the human race”.  In 2009, experts Attended a conference hosted by the Association for the Advancement of Artificial Intelligence (AAAI) to the Chat whether computers and robots might be ble 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, and that they are able to rely on their own resources. They also noted that some computer viruses can be eliminated and achieved “cockroach intelligence.” They noted that self-awareness has been limited in science fiction, but they are unlikely to be successful.  Various media sources and scientific groups.   Eliezer Yudkowskybelieves that risks of artificial intelligence are likely to occur. He also argues that research into artificial intelligence is biased by anthropomorphism . Since they base their judgments on artificial intelligence on their own experience, they claim that they underestimate the potential power of AI. He distinguishes between failures and errors of AI, which means that the algorithms prevent the AI from carrying out their intended goals, and the philosophical failure, which means that AI is programmed to realize a flawed ideology. 
Biotechnology can pose a global catastrophic risk in the form of bioengineered organisms ( viruses , bacteria , fungi , plants or animals ). In many cases the organism will be pathogen of humans, livestock , crops or other organisms we depend upon (eg pollinators or gut bacteria ). However, any organism capable of catastrophically disrupting ecosystem functions , eg highly competitive weeds , outcompeting essential crops, poses a biotechnology risk.
A biotechnology catastrophe may be caused by accidentally releasing a genetically engineered organism escaping from controlled environments, by the planned release of such an organism which then turns to be unexpected and catastrophic interactions with essential natural or agro-ecosystems, or by intentional use of biological agents in biological warfare , bioterrorism attacks.  Terrorist applications of biotechnology have historically been infrequent. To what extent is lacking in capabilities or motivation is not resolved. 
Exponential growth has been observed in the biotechnology sector and is expected to increase in biotechnological capabilities in the coming decades.  They argued That Risks from biological warfare and bioterrorism are separate from nuclear and chemical threats Because biological pathogens are Easier To mass-produce and Their Production is hard to control (especially as the technological capabilities are Becoming disponible Even to individual users). 
Given current development, more risk from novel, engineered pathogens is to be expected in the future.  Pathogens may be intentionally or unintentionally genetically modified to virulence and other characteristics.  For example, a group of Australian Researchers unintentionally changed characteristics of the mousepox virus while try trying to Develop a virus to sterilize rodents.  The modified virus has become highly lethal even in vaccinated and naturally resistant mice.   The future of the environment is not necessarily regulated. 
Noun and Chyba offers three categories of measures to reduce the risk of infection and to reduce the risk of infection. 
(See also Natural pathogens below.)
Cyberattacks have the potential to destroy everything from personal data to electric grids. Christine Peterson , co-founder and past president of the Foresight Institute , believes in cyberattack on electric grids.  Peterson also identified attacks on the Internet of Things as potentially catastrophic.
Global warming refers to the warming caused by human technology since the 19th century or earlier. Global warming is expected to change the Earth’s atmosphere and future effects. Global warming, sea level rise, and an increase in the frequency and severity of some extreme weather events and weather-related disasters. Effects of global warming includeloss of biodiversityStresses to existing food-producing systems, increased spread of known infectious diseases such as malaria, and rapid mutation of microorganisms .
It has been suggested that global runaway warming ( runaway climate change ) might cause earth to become searingly hot like Venus. In less extreme scenarios, it could cause the end of civilization as we know it. 
An environmental or 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 . An October 2017 report published in the Lancet stated that toxic air, water, soils, and workplaces have been collectively responsible for 9 million deaths worldwide in 2015, particularly from air pollution which has been linked to a growing susceptibility to non-infectious diseases, such as heart disease , stroke , and lung cancer . The report warns that the pollution crisis is beyond “the envelope on the amount of pollution of the earth can carry” and “threatens the continuing survival of human societies”. 
Most environmental 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 white without safe drinking water, pollinator decline , overfishing , massive deforestation , desertification , climate change , massive gold water pollution episodes. Detected in the early 21st century, a 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.
Mineral resource exhaustion
Romanian American economist Nicholas Georgescu-Roegen , a progenitor in economics and the paradigm founder of ecological economics , Has argued que la carrying capacity of Earth – that is, Earth’s capacity to sustain human populations and consumption levels – is bound to Decrease sometime in the future as Earth’s finite stock of mineral resources is presently being extracted and put to use; and consequent, which the world economy is heading towards an inevitable future collapse, leading to the demise of human civilization itself .  : 303fEcologist economist and steady-state theorist Herman Daly , a student of Georgescu-Roegen, has propounded the same argument by asserting that “… all we can to avoid wasting the limited capacity of creation to support present and future life. Earth]. ”  : 370
Ever since Georgescu-Roegen and Daly published these views, various scholars in the field have been discussing the existential impossibility of distributing Earth’s finite stock of mineral resources evenly among an unknown number of present and future generations. This number of generations is likely to remain unknown to us, as soon as possible . In fact, any conceivable intertemporal distribution of the stock will inevitably end up with any future point.  : 253-256  : 165  : 168-171  : 150-153  : 106-109  : 546-549  : 142-145
Experimental technology accident
Nick Bostrom suggests that in the pursuit of knowledge, humanity might inadvertently create a device that could destroy Earth and the Solar System.  Investigations in nuclear and high-energy physics could create unusual conditions with catastrophic consequences. For example, we are worried that the first nuclear test might ignite the atmosphere.   More recently, others worried that the RHIC  or the Large Hadron Collider might start a chain-reaction global disaster involving black holes, strangelets, or false vacuum states. These particular concerns have been refuted,     but the general concern remains.
Biotechnology Could lead to the establishment of a pandemic , chemical warfare Could Be taken to an extreme, nanotechnology Could lead to gray goo in qui out-of-control self-replicating robots consume all living matter on earth while building more of Themselves-in Both boxes, either deliberately or by accident. 
Many nanoscale technologies are in development or currently in use.  The only one that appears to pose a significant global catastrophe is molecular manufacturing , a technique that would make it possible to build complex structures at atomic precision.  Molecular manufacturing requires significant advances in nanotechnology, but it does not produce nanoparticles in nanofactories of desktop proportions.   When nanofactories gain the ability to produce nanofactories, production can only be limited by such abundant factors, such as input materials, energy and software. 
Molecular manufacturing, highly developed, durable weapons.  Being equipped with compact computers and motors 
Phoenix and Treder classify catastrophic risks posed by nanotechnology into three categories:
- From augmenting the development of other technologies such as AI and biotechnology.
- By enabling mass-production of potentially dangerous products that cause risk dynamics (such as arms races).
- From uncontrolled self-perpetuating processes with destructive effects.
At the same time, nanotechnology can be used to alleviate several other global catastrophic risks. 
Several researchers state that the bulk of risk from nanotechnology comes from the potential to lead to war, arms race and destructive global government.    Several reasons have been suggested why the availability of nanotech weaponry leads to unstable arms races:
- A large number of players may be tempted to enter the race since the threshold for doing so is low; 
- The ability to make weapons with molecular manufacturing 
- Therefore, lack of insight into the other parts of the game.  
- Molecular manufacturing may reduce dependency on international trade,  a potential peace-promoting factor;
- Wars of aggression can pose a smaller economic threat to the aggressor of the world. 
Since self-regulation by all state and non-state actors Seems hard to achieve achievement,  Measures to Mitigate Risks war-related-have beens Proposed Mainly in the area of international cooperation .   International infrastructure can be expanded to more sovereignty to the international level. This could help coordinate efforts for arms control. International institutions specifically dedicated to nanotechnology (perhaps analogously to the International Atomic Energy Agency IAEA ) or general arms control may also be designed.  One May aussi Jointly make differential technological progress is defensive technologies, has policy That shoulds players usually favor. The Center for Responsible Nanotechnology also suggests some technical restrictions.  Improved transparency can be another important facilitator for arms-control.
A gray goo is another catastrophic scenario, which was proposed by Eric Drexler in his 1986 book Engines of Creation  and has been a theme in mainstream media and fiction.   This scenario involves tiny self-replicating robots that consume the entire biosphere using it as a source of energy and building blocks. Nowadays, however, nanotech experts – including Drexler – discredit the scenario. According to Chris Phoenix has “so-called gray goo could only be the product of a deliberate and difficult engineering process, not an accident”. 
Warfare and Mass Destruction
The scenarios that have been explored most frequently are nuclear warfare and doomsday devices . ALTHOUGH the probability of a nuclear war per year is slim, Professor Martin Hellman HAS Described it as inevitable in the long run; unless the probability approaches zero, inevitably there will come a day when civilization’s luck runs out.  During the Cuban Missile Crisis, US President John F. Kennedy estimated the odds of nuclear war at “somewhere between one out of three and one”.  The United States and Russia have a combined arsenal of 14,700 nuclear weapons , and there is an estimated total of 15,700 nuclear weapons in existence worldwide. 
While popular perception sometimes takes nuclear war the “end of the world”, experts assign low probability to the extinction of nuclear war.   In 1982 Brian Martin Estimated That a US-Soviet nuclear exchange might kill 400-450 million Directly, mostly in the United States, Europe and Russia, and maybe Several hundred million more through follow-up consequences de ces same areas. 
Nuclear war could yield unprecedented human death tolls and habitat destruction . Detonating Such broad numbers of nuclear weapons Would Have long-term effect on the climate, Causing cold weather and Reduced sunlight That May generate significant upheaval in advanced civilizations. 
Beyond nuclear, other threats to humanity include biological warfare (BW) and bioterrorism . By contrast, chemical warfare , while able to create multiple local disasters, is unlikely to create a global one.
World population and agricultural crisis
The 20th century saw a rapid increase in human population as a result of medical developments and massive increases in productivity  such as the Green Revolution .  Between 1950 and 1984, 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 population growth Actually enabled. The energy for the Green Revolution is 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 1994 study Food, Land, Population and the US Economy the maximum US population for a sustainable economy at 200 million. “To achieve a sustainable economy and warning disaster, the United States must reduce its population by at least one-third, and the world population will be reduced by two-thirds, says the study. 
The authors of this study believe that the agricultural crisis will begin to impact after 2020, and will become critical after 2050. Geologist Dale Allen Pfeiffer claims that it can not be avoided without 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 on the wind. Should the world’s large grain producing areas become infected then there would be a crisis in the marketplace. 
Several asteroids have collided with earth in recent geological history. The Asteroid Chicxulub , for example, is theorized to have caused the extinction of the non-avian dinosaurs 66 million years ago at the end of the Cretaceous . If such an object struck Earth 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 mi) in diameter, but probably between 3 and 10 km (2-6 miles).  Asteroids with a 1 km diameter have impacted the Earth on average every 500,000 years.  Larger asteroids are less common. Small near-Earth asteroids are regularly observed.
In 1.4 million years, the star Gliese 710 is expected to start an increase in the number of meteorites in the Earth when it passes within 1.1 light years of the Sun, disturbing the cloud Oort . Dynamic models by García-Sánchez predict a 5% increase in the rate of impact.  Disrupted Objects from the Cloud Solar System.
Extraterrestrial life could invade Earth  or to exterminate and supplant human life, enslave it under a colonial system, steal the planet’s resources, or destroy the planet altogether.
ALTHOUGH evidence of alien Life Has never been documented, scientists Such As Carl Sagan -have postulated existence of extraterrestrial que la life is very Likely. In 1969, the ” Extra-Terrestrial Exposure Law ” was added to the United States 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. 
An article in The New York Times discusses the possible threats for humanity of intentionally sending messages to extraterrestrial life in the cosmos in the context of the SETI efforts. Stephen Hawking and Elon Musk have had a great deal of experience in the field of extraterrestrial civilization. 
Natural climate change
Climate change refers to Earth’s climate change. The climate has been increased in Antarctica. It has been hypothesized that there was also a period called ” snowball Earth ” when the oceans were covered in a layer of ice. These major climatic changes occurred after 10 thousand years ago before the end of the last Major Ice Age when the climate became more stable. However, abrupt climate change on the decade time scale has occurred regionally. A civilization of a climate change (colder or hotter) could pose a threat to civilization.
In the history of the earth, many ice ages are known to have occurred. More ages will be possible at an interval of 40,000-100,000 years. An ice age would have a serious impact on civilization because large 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 and water. Currently, the world is present in an interglacial period within a much older freezing event. The last glacial expansion ended over 10,000 years ago, and all civilizations evolved later than this. Scientists do not predict that a natural ice will occur anytime soon.
A number of astronomical threats have been identified. Massive objects, eg a star, a large planet or a black hole , could be catastrophic if a close encounter occurred in the Solar System. In April 2008, it was announced that two simulations of long-term planetary motion, one at Paris Observatory and the other at University of California, Santa Cruz indicate a 1% chance that MercuryIt could be made unstable by Jupiter’s gravitational pull sometime during the lifespan of the Sun. 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 Earth, all life on Earth could be obliterated: an asteroid 15 km wide is believed to have caused the extinction of the non-avian dinosaurs, while Mercury is 4,879 km in diameter. 
Another threat might come from gamma ray bursts .  Both threats are very unlikely in the future. 
A similar threat is a hypernova , produced when a hypergiant star explodes and then collapses, sending large amounts of radiation sweeping across hundreds of lightyears . Hypernovae have never been observed; however, a hypernova may have been the cause of the Ordovician-Silurian extinction events . The nearest hypergiant is Eta Carinae , approximately 8,000 light-years distant.  The hazards of various astrophysical radiation sources were reviewed in 2011. 
If the solar system was going through a dark nebula , a cloud of cosmic dust , severe global climate change would occur. 
A powerful solar flare or solar superstorm, which is a drastic and unusual decrease or increase in the Sun’s power output, could have severe consequences for life on Earth.
If our universe lies within a false vacuum , a bubble of lower-energy vacuum could come into existence by chance or otherwise in our universe, and catalyze the conversion of our universe to a lower energy state. , destroying all that we know without forewarning.  [ further explanation needed ] Such an occurrence is called a vacuum metastability event .
The magnetic poles of the earth shifted many times in geologic history. The duration of such a shift is still debated. Theories exist that during such times, the Earth’s magnetic field would be significantly weakened, threatening civilization by allowing radiation from the Sun, especially solar wind , solar flares or cosmic radiation , to reach the surface. These theories have been somewhat discredited, no statistical evidence shows for a correlation between past reversals and past extinctions.  
Numerous historical examples of pandemics  had a devastating effect on a large number of people. The present, unprecedented scale and speed of human movement makes it more difficult than ever to contain an epidemic through local quarantines . A global pandemic has become a realistic threat to human civilization.
Naturally evolving pathogens will ultimately develop an upper limit to their virulence.  Pathogen with the highest virulence, quickly killing their hosts  This simple model predicts that – virulence and transmission are not genetically linked – pathogens will evolve towards low virulence and rapid transmission. However, this is not necessarily a global disaster, for the following reasons:
1. The fitness advantage of limited virulence is primarily a function of a limited number of hosts. Any pathogen with a high virulence, high transmission rate, and long incubation time may be caused by the disease. 2. In models where virulence level and rate of transmission are related, high levels of virulence can evolve.  Virulence is instead limited by the existence of complex populations with different susceptibilities to infection, or by some hosts being geographically isolated.  The size of the host population and other strains of pathogens can also alter virulence. 3. A pathogen that infects humans as a secondary and other infections (a zoonosis ) has no constraints on its virulence in people, since the accidental secondary infections do not affect its evolution. 
Naturally arising pathogens and Neobiota
In a similar scenario to biotechnology risks, naturally evolving organisms can disrupt essential ecosystem functions.
An example of a pathogen able to global food threat is the wheat rust Ug99 .
Other examples are neobiota ( invasive species ), ie organisms that become disruptive to ecosystems once transported – often as a result of human activity – to a new geographical region. Normally the risk is a local disruption. If it is combined with serious crop failures and a global famine it may, however, pose to global catastrophic risk.
A remote possibility is a megatsunami. It has been suggested that a megatsunami caused by the collapse of a volcanic island could, for example, destroy the entire East Coast of the United States, but such predictions are based on incorrect assumptions and the likelihood of this greatly exaggerated media.  While none of these scenarios are likely to be destroyed completely, they could not There have been two recent high-fatality tsunamis-after the 2011 Tōhoku earthquake and the 2004 Indian Ocean earthquake . A megatsunami could have astronomical origins as well, such as an asteroid impact in an ocean. 
A massive flood basalt , volcanism, or the eruption of a supervolcano  could lead to so-called volcanic winter, similar to a nuclear winter . One such event, Toba eruption ,  occurred in Indonesia about 71,500 years ago. According to the Toba Disaster Theory ,  the event may have reduced human populations to only a few tens of thousands of individuals. Yellowstone Caldera is another such supervolcano, having undergone 142 or more caldera -forming eruptions in the past 17 million years. A massive volcano eruption Would eject extraordinary volumes of volcanic dust, toxic and greenhouse gases into the atmosphere with serious effects are global climate (global extreme Towards cooling, volcanic winter if short term, and ice age if long term) or global warming (if greenhouse gases were to prevail).
When the supervolcano at Yellowstone last erupted 640,000 years ago, the magma and ash ejected from the caldera most of the United States west of the Mississippi river and part of northeastern Mexico.  Another such eruption could threaten civilization.
Research published in 2011 finds evidence that massive volcanic eruptions caused massive coal combustion. Researchers have suggested that massive volcanic eruptions through coal beds in Siberia would cause a large greenhouse gas effect .  Massive eruptions can also throw away pyroclastic debris and other material in the atmosphere to a volcanic winter , as occurred on a smaller scale in 1816 following the eruption of Mount Tambora , the so-called Year Without Summer. Such an eruption may cause the deaths of millions of people, and perhaps billions of deaths  worldwide, due to the failure of the monsoon [ citation needed ] , massive scale. 
A much more speculative concept is the Verneshot : a hypothetical volcanic eruption caused by the buildup of gas deep underneath a craton . Such an event may be forceful enough to launch an extreme amount of material from the crust and mantle into a sub-orbital trajectory.
Precautions and prevention
Planetary management and compliance planetary boundaries . Within the scope of these approaches, the field of geoengineering encompasses the wide-scale debate and manipulation of the planetary environment to combat or counteract anthropogenic changes in atmospheric chemistry. Space colonization is an alternative to improve the odds of surviving an extinction scenario.  Solutions of this scope may require megascale engineering . Food storagehas been proposed globally, but the monetary cost would be high. Moreover, it would likely contribute to the current millions of deaths per year due to malnutrition . Denkenberger David and Joshua Pearce -have in Proposed Feeding Everyone No Matter What a variety of alternate foods for global catastrophic Risks Such As nuclear winter , volcanic winter , asteroid / comet impact, and abrupt climate change .  The alternative foods convert fossil fuelsor biomass (eg trees and wood ) into food. However, it is much more important that the whole population be able to survive using these methods.  Asteroid deflection has been proposed to reduce impact risk. Nuclear disarmament has been proposed to reduce the nuclear winter risk. Precautions being taken include:
- Some survivors stocking survival retreats with multiple-year food supplies.
- The Svalbard Global Seed Vault is buried 400 feet (120 m) inside the Arctic . It is designed to hold 2.5 billion seeds of more than 100 countries as a precaution to preserve the world’s crops. The surrounding rock is -6 ° C (21 ° F) (as of 2015) but the vault is kept cool at -18 ° C (0 ° F) by coolers powered by locally sourced coal.  
Global disaster risks and global governance
Insufficient global governance creates risks in the social and political domain. There are concerns of governments, the private sector, the general public and the lack of governance, and the issue of conflicting interests. This is further underlined by an understanding of the interconnectedness of global systemic risks. 
The Bulletin of the Atomic Scientists (est. 1945) is one of the oldest global risk organizations, founded after the public became alarmed by the potential of atomic warfare in the aftermath of WWII. It studies Risks associated with nuclear war and energy and famously Maintains the Doomsday Clock Established in 1947. The Foresight Institute (est. 1986) examined the Risks of nanotechnology and Its benefits. It is one of the earliest organizations to study the unintended consequences of otherwise harmless technology gone haywire at a global scale. It was founded by K. Eric Drexler who postulated ” gray goo “.  
Beginning after 2000, a growing number of scientists, billionaire philosophers and tech created organizations dedicated to studying global risks both inside and outside of academia. 
Independent non-governmental organizations include the Machine Intelligence Research Institute (2000), which aims to reduce the risk of a disaster caused by artificial intelligence and the Singularity .  The top Donors include Peter Thiel and Jed McCaleb .  The Lifeboat Foundation (2009 est.) Funds research into a disaster.  Most of the research money funds projects at universities.  The Global Catastrophic Risk Institute (2011 est.) Is a think tank for all things catastrophic risk. It is funded by the NGO Social and Environmental Entrepreneurs. TeaGlobal Challenges Foundation (est. 2012), based in Stockholm and founded by Laszlo Szombatfalvy , releases a global report on global risks.   The Future of Life Institute (est. 2014) aims to support research and initiatives for new technologies and challenges facing humanity.  Elon Musk is one of its biggest donors.  The Nuclear Threat Initiative seeks to reduce global threats from nuclear, biological and chemical threats, and containment of damage after an event.  It maintains a nuclear material security index. 
University-based organizations include the Future of Humanity Institute (2005) which researches the questions of humanity’s long-term future, particularly existential risk. It was founded by Nick Bostrom and is based at Oxford University. The Center for the Study of Existential Risk (est. 2012) is a Cambridge-based organization which studies four major risks: artificial intelligence, biotechnology, global warming and warfare. All are man-made risks, as Huw Priceexplained to the AFP news agency, “It seems a reasonable prediction that some time in this or the next century intelligence will escape from the constraints of biology”. He added that when this happens we are not going anywhere near the point of view, “and will be at the mercy of” machines that are not malicious, but machines whose interests do not include us. ”  Stephen Hawking is an acting adviser. The Millennium Alliance for Humanity and the Biosphere is a Stanford University-based organization.   It was founded by Paul Ehrlich among others. Stanford University also has the Center for International Security and Cooperation . 
Other risk assessment groups are based on governmental organizations. The World Health Organization (WHO) includes a division called the Global Alert and Response (GAR), which monitors and responds to the global epidemic crisis.  GAR helps member states with training and coordination of response to epidemics.  The United States Agency for International Development (USAID) has its Emerging Pandemic Threats Program which aims to prevent and contain naturally generated pandemics at their source.  The Lawrence Livermore National Laboratoryhas a division called the Global Security Principal Directorate which researches on behalf of the government issues such as bio-security, counter-terrorism, etc.