Day of the Bomb: Humanity's Survival After Nuclear War

Since their first and, to date, only use in 1945, nuclear weapons have been a profound source of fear. But could they actually threaten the survival of all humanity? Could they lead to our extinction? Would a full-scale nuclear war pose a threat to Earth itself?

Nuclear Bomb: Not What You May Have Thought 

Nuclear weapons operate by releasing energy from nuclear fission or fusion reactions, which involve changes in atomic nuclei, transforming them from the nuclei of one element to those of another. This differs from conventional explosives, where only the bonds between atoms are altered without changing the atoms themselves, as is typical of any chemical reaction. Consequently, nuclear weapons are exponentially more powerful than conventional bombs, typically by hundreds of thousands to millions of times. Furthermore, nuclear weapons produce radioactive radiation during detonation and disperse radioactive materials into the environment, unlike conventional explosives, meaning that their destructive impact extends beyond the immediate explosion.

It is essential to recognize that despite their immense power, nuclear weapons still emit very little energy compared to natural events on Earth. For example, earthquakes release orders of magnitude more energy than any nuclear weapons detonation. Asteroid impacts can also be far more powerful: for instance, the energy from the asteroid impact believed to have caused the extinction of the dinosaurs approximately 65 million years ago was about two million times greater than the largest nuclear bomb ever tested—this bomb itself being around 3,000 times more powerful than the one dropped on Hiroshima. Even hurricanes discharge vast amounts of energy every second, far exceeding that of a nuclear blast.

Therefore, it is clear that while human-made nuclear weapons are extraordinarily powerful, they could not destroy the Earth or cause significant physical alterations, such as shifting it from its orbit: Earth withstands much stronger shocks and remains intact. The real question is whether humanity could survive a full-scale nuclear war.

 During a nuclear reaction, atomic nuclei can transform from the nuclei of one element into those of another. Illustration of a nuclear reaction | SPL

Will a Global Nuclear War Lead to the Desruction of Humanity?

In the past, numerous nuclear explosion tests have been conducted globally: over two thousand in total, with over 500 of them taking place in the atmosphere or oceans, and the remainder underground or outside the atmosphere. The majority of these tests were carried out by the Soviet Union and the United States. Despite spanning several decades, the peak year of 1962 alone saw over one hundred nuclear tests. This wave of tests, most of which were carried out in the atmosphere above remote areas, did not significantly impact humanity: there was no noticeable increase in radiation levels, nor did these tests lead to notable climate disruptions.

It is unlikely that even a full-scale nuclear war would lead to the immediate destruction of humanity. Even if all leading nuclear powers - the United States, Russia, China, France, and the United Kingdom - were to engage in a full-scale war, many areas are likely to remain distant from nuclear weapon use sites and thus uninvolved in the conflict. People living in these unaffected areas would not be directly affected. Continents such as Africa, South America, and Australia, which do not possess nuclear weapons, are likely to experience minimal to no direct effects. Even in countries targeted by nuclear attacks, those living outside major population centers are less likely to be directly affected. There would inevitably be survivors, even in directly hit areas, as demonstrated by the fact that survivors exist from both the nuclear bombings in Japan. Despite the severe immediate effects of the bombs—intense heat radiation and powerful shockwaves—total mortality would not reach one hundred percent.

Another effect of a high-altitude nuclear explosion is the creation of an Electromagnetic Pulse (EMP). This short, powerful burst of electromagnetic energy can disrupt the operation of electrical devices. However, while EMP effects can cover a wide area, it is unlikely to impact the entire Earth. Areas not directly hit, such as Australia and South America, would probably experience minimal impact, if any.

Over two thousand nuclear tests have been conducted globally. Pictured here: the Trinity test, the first nuclear test | SPL

Nevertheless, these effects are unlikely to lead to global destruction. The immediate radiation from a nuclear explosion diminishes rapidly, and its range is relatively limited. While some nuclear fallout persists in the environment for a long time, the most dangerous radioactive products are also those that decay rapidly. Therefore, within a few weeks, the immediate danger from radiation decreases significantly. For example, two weeks after a nuclear explosion, the radiation intensity of the fallout is about one-thousandth of its level an hour after the explosion.

When nuclear weapons detonate hundreds of meters above the ground rather than directly on the surface, the fallout tends to remain in the atmosphere for a longer period and only settles on the ground later, when it is less hazardous. Today, Hiroshima and Nagasaki—the only cities in history to have been bombed with nuclear weapons—are habitable, with radiation levels comparable to average background radiation and well below levels that pose significant health risks. In both bombings, the bombs were detonated approximately 500 meters above the ground to maximize their destructive efficiency. This suggests that in a nuclear war, weapons would likely be used in a similar manner, making fallout primarily a local issue rather than a global one.

Despite the massive destruction, Hiroshima and Nagasaki are habitable today. Pictured: The atomic explosion over Nagasaki | Science Photo Library

Nuclear Weapons as an Ecological Hazard 

Nuclear bombs do not only pose immediate threats but also significant long-term ecological hazards. In fact, the most severe consequences of nuclear bombs are likely to be environmental, though scientists debate on the extent of the damage. The primary concern is the potential depletion of the ozone layer. Nuclear detonations produce large amounts of nitrogen oxides from the heating and ionization of the air. Researchers believe that in the event of a global nuclear war, these oxides could lead to the breakdown and depletion of the ozone layer globally.  This damage would be felt even in regions far from the attack sites, leading to increased incidence of sunburns and the risk of skin cancer, and likely damage agriculture by exposing essential crops to harmful ultraviolet radiation. Some researchers argue that the damage might not be as severe as predicted and that its consequences may not be catastrophic. In the 1950s and 1960s, numerous atmospheric nuclear tests were conducted, which likely contributed to the ozone hole that formed during that period; however, their contribution to ozone depletion was likely minor compared to other, more well-known factors such as chlorofluorocarbons (CFCs). Measurements taken during that period were less accurate than today, making it difficult to quantify the exact extent of the damage caused by nuclear tests.

Another potentially severe consequence is the climate change often referred to as "nuclear winter." Researchers suggest that nuclear winter would result not directly from the detonation of nuclear weapons, but from the subsequent fires. If nuclear weapons were to target cities, numerous fires and widespread firestorms would likely ensue. These fires could burn for an extended period, as firefighting systems in the affected areas would likely be inoperative. For instance, in Hiroshima, a firestorm erupted a few hours after the atomic bombing and continued to burn over a large area for a prolonged duration.

These fires would produce a lot of smoke, which would release many particles into the upper layers of the atmosphere, where they could remain for a long time, significantly reducing the intensity of sunlight reaching the Earth's surface. Most models suggest this would lead to significant cooling and a sharp decline in crop yields due to insufficient sunlight. This reduction in agricultural output could result in the most severe consequence of a global nuclear war: famine. Global food reserves would likely be exhausted before the effects subside, leading to widespread starvation that could potentially claim billions of lives. Additionally, the situation could be exacerbated by a likely collapse of international transportation and shipping systems due to fuel shortages. 

Alongside these grim scenarios, there are also alternative views suggesting that the climatic effects might not be as severe. For instance, volcanoes emit large amounts of dust but do not drastically affect the climate. Critics argue that smoke and soot might not reach high enough altitudes in the atmosphere to have a prolonged effect and would be washed away by rain. Additionally, it is argued that not all modern cities would necessarily experience firestorms as a consequence of nuclear bombs. For instance, Nagasaki did not suffer a firestorm, indicating potentially milder climate effects. Research in this field is still ongoing, reflecting ongoing debate and uncertainty about the long-term environmental consequences of nuclear warfare. 

Nuclear winter could arise due to the extensive fires. The destruction in Hiroshima after the bombing | SPL

From the Ashes, A Fire Shall be Woken

Even in the worst-case scenario, a nuclear winter is unlikely to wipe out all of humanity. The human race has survived even more severe events in the past. Massive volcanic eruptions, which inject ash into the atmosphere and create effects similar to those predicted for nuclear winter, offer a historical precedent. For example, one of the coldest years in recent centuries was 1816—the "Year Without a Summer"—which followed the massive eruption of Mount Tambora in Indonesia in 1815. That year saw a significant global temperature drop, severely affecting densely populated areas such as Europe and China, leading to crop failures and famine in parts of the world.

While the most pessimistic forecasts for a nuclear winter suggest even more drastic temperature drops than those experienced in 1816, it's important to note that even larger volcanic eruptions with severe climate impacts have occurred in prehistoric times, and humanity managed to survive. Consequently, it is reasonable to assert that a nuclear winter, while potentially devastating, would not lead to the complete extinction of humanity.

In conclusion, there is considerable confidence that a full-scale nuclear war would not result in the total extinction of humanity. However, even a relatively limited nuclear conflict could directly result in the deaths of tens or even hundreds of millions of people, potentially  triggering a catastrophic famine that could claim the lives of billions and severely damage civilization as we know it. For these reasons, it's preferable to maintain the current uncertainty rather than confirm these theories through experience.