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Existential Risks: Exploring a Robust Risk Reduction Strategy


A small but growing number of studies have aimed to understand, assess and reduce existential risks, or risks that threaten the continued existence of mankind. However, most attention has been focused on known and tangible risks. This paper proposes a heuristic for reducing the risk of black swan extinction events. These events are, as the name suggests, stochastic and unforeseen when they happen. Decision theory based on a fixed model of possible outcomes cannot properly deal with this kind of event. Neither can probabilistic risk analysis. This paper will argue that the approach that is referred to as engineering safety could be applied to reducing the risk from black swan extinction events. It will also propose a conceptual sketch of how such a strategy may be implemented: isolated, self-sufficient, and continuously manned underground refuges. Some characteristics of such refuges are also described, in particular the psychosocial aspects. Furthermore, it is argued that this implementation of the engineering safety strategy safety barriers would be effective and plausible and could reduce the risk of an extinction event in a wide range of possible (known and unknown) scenarios. Considering the staggering opportunity cost of an existential catastrophe, such strategies ought to be explored more vigorously.

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  1. 1.

    In this paper, the terms “mankind” and “humanity” refer to the sapient animals that are members of our global civilization. These are not necessarily human in the strict biological sense.

  2. 2.

    Experts at the Global Catastrophic Risk Conference suggested a 19 % chance of human extinction over the next century. Future of Humanity Institute. Global catastrophic risks survey, technical report [Internet]. 2008 Available from:

  3. 3.

    About 43 flybys, orbiting and landing missions have been sent to Mars by NASA and other nations in the past 40 years, and only 12 have been fully successful (Kaufman 2011).

  4. 4.

    For example the “Doomsday device” from Stanley Kubrick’s film Dr. Strangelove is a nuclear warhead with an amount of cobalt at its core. This metal is transmuted in the explosion into the radioactive isotope cobalt-60, which would be vaporized. This device perfectly possible to manufacture for any nation with access to nuclear weapons capacity, and would contaminate an area with lethal levels of radiation for about 60 years, since cobalt has a long half-life and a lethal levels of radiation.


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I would like to thank Seth Baum, Nick Beckstead, Jacob Haqq-Misra, Niklas Möller, Aron Vallinder and two anonymous reviewers for Risk Analysis for their comments on earlier versions of this manuscript.

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Correspondence to Karim Jebari.

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Jebari, K. Existential Risks: Exploring a Robust Risk Reduction Strategy. Sci Eng Ethics 21, 541–554 (2015).

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  • Existential risk
  • Black swan
  • Engineering safety
  • Safety barriers
  • Uncertainty
  • Shelters
  • Global catastrophe