Friday, January 18, 2019

What are the chances of a war that would exterminate most of humankind? It could be more likely than you think

Recently, together with my coworkers, I have been engaged in a statistical analysis of war over the past 600 years. The results were sobering: war, it seems, is a statistical phenomenon similar to earthquakes and forest fires. It strikes according to well defined statistical patterns and there is very little that can be done to avoid it. Aaron Clauset is another scientist who has been working on the same subject and, in a sobering analysis of his, he calculates the probablities of future wars. According to his calculations, a war as large as the Second World War has more than 40% chances to occur within 100 years from now. Then, a war causing more than billion battle deaths, that is exterminating most of humankind, has a probability of 5% to occur in less than 4 centuries from now. That doesn't mean we can relax for 4 centuries, not at all. It means we can expect it at any moment in the future.

From Aaron Clauset, 2018. (highlighting by UB)

.... a stationary model may be used to estimate the likelihood of a very large war occurring over 100 years, one like the Second World War, which produced x* = 16,634,907 battle deaths. Using the ensemble of semiparametric models for the sizes of wars and assuming a new war onset every 1.91 years on average (43), the probability of observing at least one war with x* or more deaths is p* = 0.43 ± 0.01 (Monte Carlo), and the expected number of these events over the next 100 years is 0.62 ± 0.01. Hence, under stationarity, the likelihood of a very large war over the next 100 years is not particularly small.

Under an even stronger assumption of stationarity, the model can estimate the waiting time for a war of truly spectacular size, such as one with x = 1,000,000,000 (one billion) battle deaths. A conflict this large would be globally catastrophic and would likely mark the end of modern civilization. It is also not outside the realm of possibility, if current nuclear weapons were used widely.

Using the ensemble of semiparametric models of war sizes and a longer Monte Carlo simulation, the model estimates that the median forecasted waiting time for such an event is 1339 years. Reflecting the large fluctuations that are natural under the empirical war size distribution, the distribution of waiting times for such a catastrophic event is enormously variable, with the 5 to 95% quantiles ranging from 383 to 11,489 years. A median delay of roughly 1300 years does not seem like a long time to wait for an event this enormous in magnitude, and humans have been waging war on each other, in one way or another, for substantially longer than that.


Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)