Nuclear holocaust

Etymology and usage

The English word "holocaust", derived from the Greek term "holokaustos" meaning "completely burnt", refers to great destruction and loss of life, especially by fire.

One early use of the word "holocaust" to describe an imagined nuclear destruction appears in Reginald Glossop's 1926 novel The Orphan of Space: "Moscow ... beneath them ... a crash like a crack of Doom! The echoes of this Holocaust rumbled and rolled ... a distinct smell of sulphur ... atomic destruction." In the novel, an atomic weapon is planted in the office of the Soviet dictator who, with German help and Chinese mercenaries, is preparing the takeover of Western Europe.

In the 1960s, the word principally referred to nuclear destruction. After the mid-1970s, when the word "holocaust" became closely associated with the Nazi Holocaust, references to nuclear destruction have usually spoken of "atomic holocaust" or "nuclear holocaust".

Likelihood of nuclear war

As of 2016, humanity has about 15,000 nuclear weapons, thousands of which are on hair-trigger alert. While stockpiles have been on the decline following the end of the cold war, every nuclear country is currently undergoing modernization of its nuclear arsenal. Some experts believe this modernization may increase the risk of nuclear proliferation, nuclear terrorism, and accidental nuclear war.

John F. Kennedy estimated the probability of the Cuban Missile Crisis escalating to nuclear conflict as between 33% and 50%.

In a poll of experts at the Global Catastrophic Risk Conference in Oxford (17‐20 July 2008), the Future of Humanity Institute estimated the probability of complete human extinction by nuclear weapons at 1% within the century, the probability of 1 billion dead at 10% and the probability of 1 million dead at 30%. These results reflect the median opinions of a group of experts, rather than a probabilistic model; the actual values may be much lower or higher.

Scientists have argued that even a small-scale nuclear war between two countries could have devastating global consequences and such local conflicts are more likely than full-scale nuclear war.

Moral importance of human extinction risk

In his book Reasons and Persons, philosopher Derek Parfit posed the following question:

Compare three outcomes:

1. Peace.
2. A nuclear war that kills 99% of the world’s existing population.
3. A nuclear war that kills 100%.

He continues that "Most people believe that the greater difference is between (1) and (2). I believe that the difference between (2) and (3) is very much greater." Thus, he argues, even if it would be bad if massive numbers of humans died, human extinction would itself be much worse. And given the magnitude of the calamity were the human race to become extinct, there is an overwhelming moral imperative to reduce even small risks of human extinction.

Likelihood of complete human extinction

Many scholars have posited that a global thermonuclear war may lead to human extinction, and this became scientifically plausible after nuclear winter was first conceptualized and modelled in 1983. However, models from the past decade consider total extinction very unlikely, and suggest parts of the world would remain habitable. However, the risk is not zero: short-term climate models can quickly build up uncertainties when alien conditions like nuclear winter are simulated. There could also be indirect risks, such as a societal collapse following nuclear war that can make humanity much more vulnerable to other existential threats.

Effects of nuclear war

Historically, it has been difficult to estimate the total number of casualties resulting from a global nuclear exchange because scientists are continually discovering new effects of nuclear weapons, and also revising existing models.

Early reports considered direct effects from nuclear blast and radiation and indirect effects from economic, social, and political disruption. In a 1979 report for the U.S. Senate, the Office of Technology Assessment estimated casualties under different scenarios. For a full-scale countervalue/counterforce nuclear exchange between the U.S. and the Soviet Union, they predicted U.S. deaths from 35 to 77 percent (70 million to 160 million dead at the time), and Soviet deaths from 20 to 40 percent of the population.

Although this report was made when nuclear stockpiles were at much higher levels than they are today, it also was made before the risk of nuclear winter was discovered in the early 1980s. Additionally, it did not consider other secondary effects, such electromagnetic pulses (EMP), and the ramifications they would have on modern technology and industry.

Nuclear winter

In the early 1980s, scientists began to consider the effects of smoke and soot arising from burning wood, plastics, and petroleum fuels in nuclear-devastated cities. It was speculated that the intense heat would carry these particulates to extremely high altitudes where they could drift for weeks and block out all but a fraction of the sun's light. A landmark 1983 study by the so-called TTAPS team (Richard P. Turco, Owen Toon, Thomas P. Ackerman, James B. Pollack and Carl Sagan) was the first to model these effects and coined the term "nuclear winter."

More recent studies make use of modern global circulation models and far greater computer power than was available for the 1980s studies. A 2007 study examined consequences of a global nuclear war involving moderate to large portions of the current global arsenal. The study found cooling by about 12–20 °C in much of the core farming regions of the US, Europe, Russia and China and as much as 35 °C in parts of Russia for the first two summer growing seasons. The changes they found were also much longer lasting than previously thought, because their new model better represented entry of soot aerosols in the upper stratosphere, where precipitation does not occur, and therefore clearance was on the order of 10 years. In addition, they found that global cooling caused a weakening of the global hydrological cycle, reducing global precipitation by about 45%.

The authors did not discuss the implications for agriculture in depth, but noted that a 1986 study which assumed no food production for a year projected that "most of the people on the planet would run out of food and starve to death by then" and commented that their own results show that, "This period of no food production needs to be extended by many years, making the impacts of nuclear winter even worse than previously thought."

In contrast to the above investigations of global nuclear conflicts, studies have shown that even small-scale, regional nuclear conflicts could disrupt the global climate for a decade or more. In a regional nuclear conflict scenario where two opposing nations in the subtropics would each use 50 Hiroshima-sized nuclear weapons (about 15 kiloton each) on major populated centres, the researchers estimated as much as five million tons of soot would be released, which would produce a cooling of several degrees over large areas of North America and Eurasia, including most of the grain-growing regions. The cooling would last for years, and according to the research, could be "catastrophic". Additionally, the analysis showed a 10% drop in average global precipitation, with the largest losses in the low latitudes due to failure of the monsoons.

Regional nuclear conflicts could also inflict significant damage to the ozone. A 2008 study found that a regional nuclear weapons exchange could create a near-global ozone hole, triggering human health problems and impacting agriculture for at least a decade. This effect on the ozone would result from heat absorption by soot in the upper stratosphere, which would modify wind currents and draw in ozone-destroying nitrogen oxides. These high temperatures and nitrogen oxides would reduce ozone to the same dangerous levels we now experience below the ozone hole above Antarctica every spring.

Nuclear famine

It is difficult to estimate the number of casualties that would result from nuclear winter, but it is likely that the primary effect would be global famine (known as Nuclear Famine), wherein mass starvation occurs due to disrupted agricultural production and distribution. In a 2013 report, the International Physicians for the Prevention of Nuclear War (IPPNW) concluded that more than two billion people, about a third of the world's population, would be at risk of starvation in the event of a regional nuclear exchange between India and Pakistan, or by the use of even a small proportion of nuclear arms held by US and Russia. Several independent studies show corroborated conclusions that agricultural outputs will be significantly reduced for years by climatic changes driven by nuclear wars. Reduction of food supply will be further exacerbated by rising food prices, affecting hundreds of millions of vulnerable people, especially in the poorest nations of the world.

Electromagnetic pulse

An electromagnetic pulse (commonly abbreviated as EMP, pronounced /iː.ɛm.piː/) is a burst of electromagnetic radiation. Nuclear explosions create a pulse of electromagnetic radiation called a nuclear EMP or NEMP. Such EMP interference is known to be generally disruptive or damaging to electronic equipment. If a single nuclear weapon "designed to emit EMP were detonated 250 to 300 miles up over the middle of the country it would disable the electronics in the entire United States."

Given that many of the comforts and necessities we enjoy in the 21st century are predicated on electronics and their functioning, an EMP would disable hospitals, water treatment facilities, food storage facilities, and all electronic forms of communication. An EMP blast threatens the foundation which supports the existence of the modern human condition. Certain EMP attacks could lead to large loss of power for months or years. Currently, failures of the power grid are dealt with using support from the outside. In the event of an EMP attack, such support would not exist and all damaged components, devices, and electronics would need to be completely replaced.

In 2013, the US House of Representatives considered the "Secure High-voltage Infrastructure for Electricity from Lethal Damage Act" that would provide surge protection for some 300 large transformers around the country. The problem of protecting civilian infrastructure from electromagnetic pulse has also been intensively studied throughout the European Union, and in particular by the United Kingdom. While precautions have been taken, James Woolsey and the EMP Commission suggested that an EMP is the most significant threat to the U.S. The greatest threat to human survival in the aftermath of an EMP blast would be the inability to access clean drinking water. For comparison, in the aftermath of the 2010 Haitian earthquake, the water infrastructure had been devastated and led to at least 3,333 deaths from cholera in the first few months after the earthquake. Other countries would similarly see the resurgence of previously non-existent diseases as clean water becomes increasingly scarce.

The risk of an EMP, either through solar or atmospheric activity or enemy attack, while not dismissed, was suggested to be overblown by the news media in a commentary in Physics Today. Instead, the weapons from rogue states were still too small and uncoordinated to cause a massive EMP, underground infrastructure is sufficiently protected, and there will be enough warning time from continuous solar observatories like SOHO to protect surface transformers should a devastating storm be detected.

Origins and analysis of extinction hypotheses

As a result of the extensive nuclear fallout of the 1954 Castle Bravo nuclear detonation, author Nevil Shute wrote the popular novel On the Beach which was released in 1957, in this novel so much fallout is generated in a nuclear war that all human life is extinguished. However the premise that all of humanity would die following a nuclear war and only the "cockroaches would survive" is critically dealt with in the 1988 book Would the Insects Inherit the Earth and Other Subjects of Concern to Those Who Worry About Nuclear War by nuclear weapons expert Philip J. Dolan.

In 1982 nuclear disarmament activist Jonathan Schell published The Fate of the Earth, which is regarded by many to be the first carefully argued presentation that concluded that extinction is a significant possibility from nuclear war. However, the assumptions made in this book have been thoroughly analyzed and determined to be "quite dubious". The impetus for Schell's work, according to physicist Brian Martin, was to argue that "if the thought of 500 million people dying in a nuclear war is not enough to stimulate action, then the thought of extinction will. Indeed, Schell explicitly advocates use of the fear of extinction as the basis for inspiring the "complete rearrangement of world politics".

The belief in "overkill" is also commonly encountered, with an example being the following statement made by nuclear disarmament activist Philip Noel-Baker in 1971 – "Both the US and the Soviet Union now possess nuclear stockpiles large enough to exterminate mankind three or four – some say ten – times over". Brian Martin suggested that the origin of this belief was from "crude linear extrapolations", and when analyzed it has no basis in reality. Similarly, it is common to see stated that the combined explosive energy released in the entirety of World War II was about 3 megatons, while a nuclear war with warhead stockpiles at Cold War highs would release 6000 WWII's of explosive energy. An estimate for the necessary amount of fallout to begin to have the potential of causing human extinction is regarded by physicist and disarmament activist Joseph Rotblat to be 10 to 100 times the megatonnage in nuclear arsenals as they stood in 1976; however, with the world megatonnage decreasing since the Cold War ended this possibility remains hypothetical.

According to the 1980 United Nations report General and Complete Disarmament: Comprehensive Study on Nuclear Weapons: Report of the Secretary-General, it was estimated that there were a total of about 40,000 nuclear warheads in existence at that time, with a potential combined explosive yield of approximately 13,000 megatons.

By comparison, in the Timeline of volcanism on Earth when the volcano Mount Tambora erupted in 1815 – turning 1816 into the Year Without A Summer due to the levels of global dimming sulfate aerosols and ash expelled – it exploded with a force of roughly 800 to 1,000 megatons, and ejected 160 km³ (38 cu mi) of mostly rock/tephra, which included 120 million tonnes of sulfur dioxide as an upper estimate. A larger eruption, approximately 74,000 years ago, in Mount Toba produced 2,800 km³ (670 cu mi) of tephra, forming lake Toba, and produced an estimated 6,000 million tonnes (6.6×10⁹ short tons) of sulfur dioxide. The explosive energy of the eruption may have been as high as equivalent to 20,000,000 megatons (Mt) of TNT, while the Chicxulub impact, connected with the extinction of the dinosaurs, corresponds to at least 70,000,000 Mt of energy, which is roughly 7000 times the maximum arsenal of the US and Soviet Union.

However, it must be noted that comparisons with supervolcanos are more misleading than helpful due to the different aerosols released, the likely air burst fuzing height of nuclear weapons and the globally scattered location of these potential nuclear detonations all being in contrast to the singular and subterranean nature of a supervolcanic eruption. Moreover, assuming the entire world stockpile of weapons were grouped together, it would be difficult due to the nuclear fratricide effect to ensure the individual weapons would go off all at once. Nonetheless, many people believe that a full-scale nuclear war would result, through the nuclear winter effect, in the extinction of the human species, though not all analysts agree on the assumptions inputted into these nuclear winter models.