Global catastrophic risk
A global catastrophic risk or a doomsday scenario is a hypothetical event that could damage human well-being on a global scale, endangering or even destroying modern civilization. Existential risk is a related term limited to events that could cause full-blown human extinction or permanently and drastically curtail humanity's existence or potential.
In the 21st century, a number of academic and non-profit organizations have been established to research global catastrophic and existential risks, formulate potential mitigation measures, and either advocate for or implement these measures.
Definition and classification
Defining global catastrophic risks
The term global catastrophic risk "lacks a sharp definition", and generally refers to a risk that could inflict "serious damage to human well-being on a global scale".Humanity has suffered large catastrophes before. Some of these have caused serious damage but were only local in scope—e.g. the Black Death may have resulted in the deaths of a third of Europe's population, 10% of the global population at the time. Some were global, but were not as severe—e.g. the 1918 influenza pandemic killed an estimated 3–6% of the world's population. Most global catastrophic risks would not be so intense as to kill the majority of life on earth, but even if one did, the ecosystem and humanity would eventually recover.
Similarly, in Catastrophe: Risk and Response, Richard Posner singles out and groups together events that bring about "utter overthrow or ruin" on a global, rather than a "local or regional" scale. Posner highlights such events as worthy of special attention on cost–benefit grounds because they could directly or indirectly jeopardize the survival of the human race as a whole.
Defining existential risks
Existential risks are defined as "risks that threaten the destruction of humanity's long-term potential." The instantiation of an existential risk would either cause outright human extinction or irreversibly lock in a drastically inferior state of affairs. Existential risks are a sub-class of global catastrophic risks, where the damage is not only global but also terminal and permanent, preventing recovery and thereby affecting both current and all future generations.Non-extinction risks
While extinction is the most obvious way in which humanity's long-term potential could be destroyed, there are others, including unrecoverable ''collapse and unrecoverable dystopia''. A disaster severe enough to cause the permanent, irreversible collapse of human civilisation would constitute an existential catastrophe, even if it fell short of extinction. Similarly, if humanity fell under a totalitarian regime, and there were no chance of recovery, then such a dystopia would also be an existential catastrophe. Bryan Caplan writes that "perhaps an eternity of totalitarianism would be worse than extinction". A dystopian scenario shares the key features of extinction and unrecoverable collapse of civilization: before the catastrophe humanity faced a vast range of bright futures to choose from; after the catastrophe, humanity is locked forever in a terrible state.Potential sources of risk
Potential global catastrophic risks are conventionally classified as anthropogenic or non-anthropogenic hazards. Examples of non-anthropogenic risks are an asteroid or comet impact event, a supervolcanic eruption, a natural pandemic, a lethal gamma-ray burst, a geomagnetic storm from a coronal mass ejection destroying electronic equipment, natural long-term climate change, hostile extraterrestrial life, or the Sun transforming into a red giant star and engulfing the Earth billions of years in the future.Anthropogenic risks are those caused by humans and include those related to technology, governance, and climate change. Technological risks include the creation of artificial intelligence misaligned with human goals, biotechnology, and nanotechnology. Insufficient or malign global governance creates risks in the social and political domain, such as global war and nuclear holocaust, biological warfare and bioterrorism using genetically modified organisms, cyberwarfare and cyberterrorism destroying critical infrastructure like the electrical grid, or radiological warfare using weapons such as large cobalt bombs. Other global catastrophic risks include climate change, environmental degradation, extinction of species, famine as a result of non-equitable resource distribution, human overpopulation or underpopulation, crop failures, and non-sustainable agriculture. Experts are also increasingly worried about cascading risks, the use of AI for bioengineering or in nuclear weapons systems, and a variety of other threats.
Methodological challenges
Research into the nature and mitigation of global catastrophic risks and existential risks is subject to a unique set of challenges and, as a result, is not easily subjected to the usual standards of scientific rigour. For instance, it is neither feasible nor ethical to study these risks experimentally. Carl Sagan expressed this with regards to nuclear war: "Understanding the long-term consequences of nuclear war is not a problem amenable to experimental verification". Moreover, many catastrophic risks change rapidly as technology advances and background conditions, such as geopolitical conditions, change. Another challenge is the general difficulty of accurately predicting the future over long timescales, especially for anthropogenic risks which depend on complex human political, economic and social systems. In addition to known and tangible risks, unforeseeable black swan extinction events may occur, presenting an additional methodological problem.Lack of historical precedent
Humanity has never suffered an existential catastrophe and if one were to occur, it would necessarily be unprecedented. Therefore, existential risks pose unique challenges to prediction, even more than other long-term events, because of observation selection effects. Unlike with most events, the failure of a complete extinction event to occur in the past is not evidence against their likelihood in the future, because every world that has experienced such an extinction event has gone unobserved by humanity. Regardless of civilization collapsing events' frequency, no civilization observes existential risks in its history. These anthropic issues may partly be avoided by looking at evidence that does not have such selection effects, such as asteroid impact craters on the Moon, or directly evaluating the likely impact of new technology.To understand the dynamics of an unprecedented, unrecoverable global civilizational collapse, it may be instructive to study the various local civilizational collapses that have occurred throughout human history. For instance, civilizations such as the Roman Empire have ended in a loss of centralized governance and a major civilization-wide loss of infrastructure and advanced technology. However, these examples demonstrate that societies appear to be fairly resilient to catastrophe; for example, Medieval Europe survived the Black Death without suffering anything resembling a civilization collapse despite losing 25 to 50 percent of its population.
Incentives and coordination
There are economic reasons that can explain why so little effort is going into global catastrophic risk reduction. First, it is speculative and may never happen, so many people focus on other more pressing issues. It is also a global public good, so we should expect it to be undersupplied by markets. Even if a large nation invested in risk mitigation measures, that nation would enjoy only a small fraction of the benefit of doing so. Furthermore, global catastrophic risk reduction can be thought of as an intergenerational global public good. Since most of the hypothetical benefits of the reduction would be enjoyed by future generations, and though these future people would perhaps be willing to pay substantial sums for risk reduction, no mechanism for such a transaction exists.Cognitive biases
Numerous cognitive biases can influence people's judgment of the importance of existential risks, including scope insensitivity, hyperbolic discounting, the availability heuristic, the conjunction fallacy, the affect heuristic, and the 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, the quantity they are willing to give does not increase linearly with the magnitude of the issue: people are roughly as willing to prevent the deaths of 200,000 or 2,000 birds. Similarly, people are often more concerned about threats to individuals than to larger groups.
Eliezer Yudkowsky theorizes that scope neglect plays a role in public perception of existential risks:
Substantially larger numbers, such as 500 million deaths, and especially qualitatively different scenarios such as the extinction of the entire human species, seem to trigger a different mode of thinking... People who would never dream of hurting a child hear of existential risk, and say, "Well, maybe the human species doesn't really deserve to survive".
All past predictions of human extinction have proven to be false. To some, this makes future warnings seem less credible. Nick Bostrom argues that the absence of human extinction in the past is weak evidence that there will be no human extinction in the future, due to survivor bias and other anthropic effects.
Sociobiologist E. O. Wilson argued that: "The reason for this myopic fog, evolutionary biologists contend, is that it was actually advantageous during all but the last few millennia of the two million years of existence of the genus Homo... A premium was placed on close attention to the near future and early reproduction, and little else. Disasters of a magnitude that occur only once every few centuries were forgotten or transmuted into myth."