Comparing Catastrophes: How Would a Global and a “Small” Nuclear War Impact Our Planet?

Nuclear war is a common theme of many dystopian films and computer games. Societal collapse, limited food and water, and all-out violence being common themes. 

But just how accurate are these depictions of the aftermath? 

Let's find out. 

But, before we get into that, it is worthwhile spending a little time looking into what actually happens when a single nuclear weapon explodes. 

What is the impact of a nuclear explosion?

Nuclear explosions are one of the most intense and destructive things ever witnessed by our species.

Beyond the myriad of natural disasters like asteroid impacts, volcanic explosions, earthquakes, and tsunamis (to name but some examples) there are not many other things that come close to a nuclear explosion for sheer destructive power. 

These events produce immediate, delayed, and long-term impacts that can, and will, devastate large areas around the point of detonation and far beyond.

To give you an idea of the sheer destructive potential of these weapons, let's track what happens when one of them goes off. While we'll try to give a rough overview below, the actual effects of a nuclear explosion depend entirely on its yield, type, and the altitude of detonation.

Airburst explosions, or sub-surface explosions, for example, will have different characteristics to ones that impact the surface. 

In this example, we'll detonate an 800 kt bomb airburst warhead at a height of about 1,600 feet (500 meters) from the ground. This is a relatively large bomb for most modern arsenals and is around 100 times more powerful than the first atomic bomb dropped on Hiroshima in WW2. 

So, let's blow it up over a city, shall we? 

Once the nuclear weapon reaches its target or is otherwise detonated (i.e. "ground zero"), an enormous fireball forms within a fraction of a second. Initially, most of the thermal radiation (roughly a third of all the energy released) is used to heat the nuclear material in the weapon, with temperatures reaching that similar to the interior of the sun, about 100,000,000 degrees Celsius.

This fireball reaches roughly 0.5 miles (just over 800 meters) in diameter, and will effectively vaporize everything (buildings and people) instantly. 

Shortly after (still within fractions of a second) intense pulses of thermal radiation emerge from the fireball. At the same time, a wave of high-pressure moves outwards at several times the speed of sound 2,000 mph (3,218.69 km/h).

The thermal radiation blast comes in two main phases, with the first lasting about a tenth of a second in the ultraviolet region. The second, far more deadly pulse, lasts several seconds and carries about 99% of the total thermal energy output of the explosion. 

This heatwave stretches out in all directions, rising temperatures near the center of the blast to around 300,000 degrees Celsius (540,000 degrees Fahrenheit). To put that into perspective, that is 300 times hotter than the temperature bodies are cremated at, so humans are almost instantly reduced to their most basic minerals.

Exposure to this will result in 1st-degree burns for those who are 7-miles (11 km) away, second-degree burns in those at around 6-miles distance (9.7 km), and third-degree burns in those who are 5-miles (8 km) distance from the blast. Any closer than about 1.8 miles (3 km) and you'll likely be completely incinerated. The intense light released can, and will, also blind you permanently. 

If close enough to the blast, anything that can burn will burn (like clothes and skin), and other materials, like sand, will melt and turn to glass. Every living thing within range of the blast will be killed instantly. This may, or may not, result in an intense firestorm also forming. 

It is important to note, however, that the severity of thermal radiation damage depends very strongly on weather conditions. For example, clouds or smoke in the air can considerably reduce effective damage ranges versus clear air conditions.

Mercifully, most people will likely be indoors when the bomb detonates, momentarily sheltering them from the worst of the heatwave. But, this will only be a very short reprieve. 

All pretty nasty, but this is just the calm before the storm.

The heatwave is shortly followed by the blast wave that also moves out in all directions producing a wall of fast-moving highly compressed air that smashes everything in its path. Blast energy constitutes roughly half of all the energy released by the detonation and is usually measured in pounds per square inch (psi). 

Within roughly 1.2 miles (2 km) of "ground zero", most buildings will be blown to pieces by this wave. For a city with a population of around 4 million people, the combined heat and pressure wave will kill something like 120,000 people immediately. 

The air behind the shock front is accelerated to high velocities, generating a very powerful wind that, in turn, creates dynamic pressure against any objects facing them. 

"Shock waves cause a virtually instantaneous jump in pressure at the shock front. The combination of the pressure jump (called the overpressure) and the dynamic pressure causes blast damage. Both the overpressure and the dynamic pressure reach their maximum values upon the arrival of the shock wave," explains the Atomic Archive. 

Buildings will be leveled, trees felled, and anything not strong enough to withstand the power of the wave is otherwise demolished for miles around within less than a minute after the explosion. Worse still, any buildings that were destroyed now help shatter the rest of the city.

Their constituent parts become massive flying projectiles that cause even more damage by raining down on the city as their kinetic energy falls enough for gravity to take over crushing anything, and anyone unlucky enough to be in the way. 

Eventually, the pressure wave decays over a period ranging from a few tenths of a second to several seconds. Towards the maximum blast radius of the bomb (roughly 11.4 miles/18.4km for 800kt), the pressure wae will be around 1 psi, which is enough to shatter windows.

Shortly after the fireball forms and begins to collapse, the characteristic mushroom cloud is formed and a strong updraft carries radioactive particles, dust, and debris high into the air. The size and height of this cloud depend entirely on the yield of the weapon and can stretch as high as 6-8 miles above the Earth's surface. 

At this height, the cloud tends to spread out over a large area. But the fun has only just begun, the remaining 15%, give or take, of the bomb's energy is yet to be unleashed in the form of radiation.  

On top of this, under some conditions, the many individual fires created by a nuclear explosion can combine into one massive "firestorm." This happens when many small fires heat the air and cause hurricane strength winds directed inward toward the fire.

What are the effects of radiation from nuclear explosions? 

The last piece of the puzzle, and one fairly unique to nuclear explosions, as opposed to conventional weapons, is the release of nuclear radiation. Several kinds are emitted (alpha, beta, gamma/ionizing radiation) over the immediate-term and long-term after detonation. 

Initially, large amounts of gamma and neutron radiation are released from the explosion. The concentration of this decreases with distance from ground zero, with less than 1 Roentgen (1 J/kg or 100 rad) exposure beyond about 5 miles (8 km) distance. 

The amount of this released depends entirely on the weapon's yield, and only represented about 3% of the total energy released from the explosion. You will receive lethal doses if caught within range, but would be killed anyway by the heat and blast waves before your radiation exposure becomes a "problem". 

By far the largest concern when it comes to radiation from nuclear explosions is the long-term residual nuclear radiation, aka "fallout". This kind of radiation comes from the weapon debris, fission products, and, in the case of a ground burst, radiated soil.

There are about 300 different types of dangerous fission products that can form from a nuclear explosion, all of which have widely varying half-lives. 

Some are very short, i.e., fractions of a second, while a few are long enough that the materials can be a hazard for anywhere from months to hundreds of years. Their principal mode of decay is the emission of beta particles and gamma radiation.

Initially, large amounts of dust and ash produced by the explosion will have high amounts of highly radioactive material within them. This is especially the case if the dust and ash originated near "ground zero". 

This dust and ash can travel very far and over a very long range downwind from the point of detonation. How far and over what area it travels will depend largely on weather conditions at the time, and where the blast occurred.

Since the example explosion we've used is for an airblast detonation, it will produce significantly less ash and dust than a surface explosion. If it were a surface blast, the death toll from fallout alone could surpass that from the fireball, heat, and pressure wave described above. However, the fallout will still be pretty significant. 

Over time, dust and ash will rain down on the ground below, blanketing everything in sight. Most particles are also small enough to be inhaled. 

Theoretically, exposure to this can be reduced significantly by sheltering underground in places like bomb shelters or basements. This is especially the case in the first few critical hours and days after the blast. 

Unfortunately, while structures like fallout shelters were relatively common during the Cold War, very few people build them or maintain them today. Especially those with specialized air filtration systems. 

Exposure to the radiation products impacts the human body in several different kinds of ways and is dependant on the size of the dose received, how the radiation affects human tissue, and which organs were exposed. Of these, the dose is the most important and is usually assessed using units called rads, which are the amount of radiation that releases an energy of 100 ergs per gram of matter. 

Another unit of radiation is the rem or Roentgen equivalent in man. This is the absorbed dose (in rads) multiplied by the quality factor of the type of radiation. Anything above 400 rem is usually fatal fairly quickly. A dose of 200-300 rem will cause serious radiation sickness effects and will be lethal to  10-35% of the people affected after 30 days; whereas less than 20 rem is almost always survivable but may lead to some form of long-term chromosomal damage. 

Radiation poisoning affects people in different ways, but some of the most common symptoms include nausea and vomiting, spontaneous bleeding, diarrhea, and severe skin burns. 

Effects on organs vary widely, with those that reproduce quickly the most impacted. Vomiting and fatigue, for example, is one of the first indications of exposure to 200 rems or more, with hair loss following soon after. At less than 100 rem, there is a temporary reduction in white blood cells, leaving victims more susceptible to infections. 

The brain tends to require 5,000 rems or more to be permanently damaged, although this level of exposure usually leads to rapid death from organ failure. Other organs, like the thyroid, are very susceptible to radiation exposure, especially to radioactive iodine, leading to some very serious health problems. Taking potassium iodide can reduce the effects of exposure.

If exposure is serious enough, radiation sickness takes roughly a week to kill someone, so the initial death count from a nuclear explosion is only the beginning of the story. If people don't receive a high enough dose of radiation to kill them quickly, they can still suffer from some serious health issues many years later. Malignant tumors, keloids, cataracts, etc, are all common long-term problems. 

And that is if they survive the aftermath of what comes with a destroyed city like fires, food, water, and fuel shortages, serious physical injuries like blunt force trauma, breakdown of social order, diseases caused by polluted water, etc. For this reason, many others will die from disease and untreated injuries as emergency series struggle to find and help people.

All pretty horrendous stuff. But, such an event could never happen today, right?

How likely is a nuclear attack today? 

As we've discussed earlier, fewer and fewer people now build fallout shelters on their property compared to only a few decades ago. This is, in part, due to the fact that people are, generally speaking, less anxious about a potential nuclear attack. 

Schools, on the whole, also rarely, if ever, provide nuclear attack drills in the classroom, as they did during the Cold War (although those in areas where tornadoes are common will have tornado or storm shelters). While tensions around a future global war are sometimes on the rise, most people don't believe a large-scale nuclear exchange is very likely. 

This is good in a way, as reduced tension around a potential nuclear war reduces the potential for mistakes or pre-emptive strikes taking place. However, nuclear weapons still remain one of the greatest threats to our species. 

Unlike natural disasters, the potential use of nuclear weapons, and the associated devastation they would bring, are completely in our hands. So, how likely is a nuclear war today? 

As it happens we seem to be entering a new era in nuclear weapon history. Many treaties that were brokered to attempt to control the numbers of viable nuclear weapons are coming to the end of their term.

Treaties like the Anti-ballistic Missile Treaty, Intermediate-range Nuclear Forces Treaty, Start 1, SORT, and New Start have either expired, not been renewed, have been withdrawn from, or are due to expire very soon. This could result in a new arms race of sorts commencing once again. 

This is, in part, due to the emergence of some new technologies that may give one nuclear capability a considerable advantage over others. Hypersonic missiles are one example. 

Conventional intercontinental ballistic missiles (ICBMs) travel into sub-orbital space, release their payloads (or re-entry platforms) and eventually rain down nuclear warheads on their targets. Since they have a relatively high angle trajectory, they can be detected over the horizon using technology like radar. 

This gives a defending nation some time to assess the situation and act accordingly. Hypersonic missiles, on the other hand, are able to travel through the atmosphere are relatively low altitudes. 

This means they can remain undetected for longer, and since they also travel at very high speeds (roughly 5 times the speed of sound), this gives a defending nation much less time to react to an attack. And this is the critical point. 

Some of the most dangerous times in our history, with regards to nuclear weapons, occurred when actions were taken to reduce the possible reaction time of an opponent. Think of the "Cuban Missile Crisis". 

This led to heightened tensions between the Soviet Union and the United States, bringing the world as close to an all-out nuclear exchange as any other time in history. 

Hypersonic weapons could lead to heightened anxiety among nuclear powers which may, in turn, increase the likelihood of accidents occurring. Or, indeed, a rash decision by one or more governments. 

There is also the problem of some smaller weapons that blur the line between conventional and nuclear weapons. 

However, there is another piece of the puzzle — public opinion. Politicians, who ultimately make policies and determine whether to use nuclear weapons, are very sensitive to what the people think about things like nuclear weapons. After all, they want to be elected or re-elected when the time comes. 

Most people, whether they believe nukes have made the world safer or not, generally agree that the risk posed by these weapons is huge. They also tend to agree that actions should be taken to reduce the risk, like fewer nations having access to them, or reducing arsenal sizes, etc. 

If enough public pressure can be put on decision-makers to either extend, repledge to, or draw up new nuclear treaties, like the "No First Use" treaty, it would go a long way to reducing tensions between nations. 

But, treaties are only, ultimately, pieces of paper. They can't physically stop a nation from firing off its nukes. So what would be the consequences of a nuclear exchange to the planet?  

What would be the consequences of large-scale nuclear war? 

We've seen the impact of a single nuclear explosion on a city, and tough reading it is. But, what about scaling up the problem to a large-scale nuclear exchange on a global scale. 

What would the damage be? 

Often also referred to as a "nuclear holocaust", this scenario would see most nuclear powers unleashing some, or all, of their nuclear weapons on cities and other military sites on every major continent on the planet. 

But surely there aren't enough nukes to do that? Think again. 

To date, there are roughly 10,000 major cities worldwide, and each would require only about 1 moderately-sized thermonuclear warhead to effectively render it uninhabitable. Back in 1986, there were roughly 70,000 warheads on the planet, but this has been reduced significantly in recent years to roughly 14,000 today.

That is more than enough to effectively destroy every single major city on Earth. However, in a genuine exchange of weapons, most powers will target only their opponent's largest cities and critical infrastructure like military installations, power plants, etc. 

So, what would the world look like after the dust has settled, so to speak? You might have an idea in your mind's eye from all those disaster movies and games you've been exposed to, but many experts believe even these bleak visions might be too optimistic. 

For example, Alan Robock, an environmental sciences professor at Rutgers University, believes things could get a lot worse than even your worst nightmares. 

He has spent decades trying to understand what a nuclear war would do to the planet. The sum of his work, along with other colleagues, is based on economic, scientific, and agricultural models.

His findings? Well, most of us would probably die. Not exactly encouraging, but why? 

As we have seen, any targeted sites would be effectively wiped off the map within a few minutes killing most people nearby in short order. That's bad enough, but the main impact on the planet would be what happens months to years later. 

Since our modern world is so reliant on technology, this would be one of the first things to go. Many electronic devices and networks like the internet would likely be severely damaged from the electromagnetic pulses associated with nuclear explosions. But, even this pales in comparison to the impact of basic necessities for life. 

The most devastating long-term effects of nuclear war actually come down to the black smoke, along with the radioactive dust and particulates in the air, that attacks produce.

Widespread firestorms would rage, and the large amounts of dust kicked up into the atmosphere would lead to what is generally known as nuclear winter. This would, according to some studies, lead to a dramatic drop in global temperatures for several years, directly impacting agriculture and leading to potential famines in many parts of the globe. 

Studies conducted during the Cold War have suggested that while millions of people would be killed instantly, most would survive the initial exchange, albeit only for a short time. Nuclear fallout and other indirect consequences, like societal and economic collapse, might be enough to push our species to the brink of extinction. 

Such an event would be a worst-case scenario and by most accounts would require the United States and Russia (who between them have most of the world's nukes) to unleash a good portion of their arsenals. 

Many areas of the world would effectively see all of their major cities and associated infrastructure destroyed. Life as their citizens know it would cease to exist and quickly descend into chaos. But the damage would also impact other nations around the world too. 

Such an exchange would kick up around 150 million tons of black smoke, rising from burning cities and other areas, which would spread to most of the planet over a period of weeks. Global temperatures would drop for years to come, with the Northern Hemisphere likely suffering the worst of it. 

Precipitation around the world would also be reduced, perhaps as much as 45 percent, according to some studies. This combination of reduced sunlight and access to freshwater would reduce crop yields significantly. 

Starvation and famine would certainly follow. 

The aftermath would also deplete the ozone layer, enabling dangerous levels of ultraviolet light to reach the ground. That would harm nearly every ecosystem and make it harder for some humans to go outside, especially those with paler skin. 

However, the seriousness of such a scenario is hotly debated. In 1990, the scientists who first coined the phrase “nuclear winter” said their original findings were overblown and that a large-scale nuclear war wouldn’t extinguish humanity. 

Another government-backed study by Jon Reisner also found that the impact of smoke in the atmosphere would be bad, but not as dire as more pessimistic analyses have concluded.

Whatever the case, a large-scale nuclear war would almost certainly affect hundreds of millions or billions of people not directly caught in the fighting. 

For other lifeforms on Earth, the impact would be very serious initially, but is unlikely to make many species extinct. Previous mass extinction events have required much more serious impacts on the planet, such as asteroid impacts. 

The asteroid that killed off the dinosaurs (Chicxulub), for example, was roughly equivalent to 2,000,000 of the largest nuclear warheads ever built - the Tsar Bombas (50 megatons of TNT each). This is far larger than the entire combined destructive potential of all nuclear weapons currently in existence. 

While this was not a nuclear explosion, per se, the aftermath of the impact shares many characteristics with what would happen after a large-scale nuclear war. 

However, most predictions of the aftermath are just that, predictions. We could only ever know for sure if it actually happened, and we'd all have bigger things to worry about than who was right or wrong.

What would be the effect of a small-scale nuclear exchange? 

The effects of a large-scale nuclear exchange are, clearly, pretty bad, but surely a small-scale nuclear war wouldn't be so bad, right? 

Sadly, that appears to be far too optimistic. 

If, say, some of the smaller nuclear powers like India and Pakistan were to "go nuclear", even that would have pretty serious implications for the rest of the planet.

Termed by some as a "nuclear autumn", detonating just a handful of nukes isn't something any of us want to witness in our lifetimes. Fifty Hiroshima-sized bombs going off would release enough dust and smoke to appreciably reduce global temperatures to a level akin to the so-called "Litte Ice Age" from the early 14th century through the mid-19th centuries, so some studies have shown. 

While a milder cooling when compared to a "nuclear winter", would affect the climate enough to severely impact agriculture and likely result in a global food shortage. According to some estimates, around 5- to 6-million tons of fine particulate matter would be dumped into the stratosphere if India and Pakistan unloaded all of their nuclear arsenals against one another. 

With that much particulate matter in the stratosphere, American and Chinese food production, especially corn and wheat, would drop by between 20 and 40 percent over the first 5 years. It is also possible that global cooling would last at least a decade, plunging temperatures to lower than anything seen in the past 1,000 years. 

This would risk the lives of around 2 billion people from famine, with most of those being located in Southeast Asia, Latin America, North America, and Europe. This wouldn't threaten our species as a whole, but modern life as we know it would definitely not be sustainable. 

Any serious pressure on food supplies would likely cause hyperinflation in the prices of any food that can be harvested, adding additional pressure between other nations on the planet. This would most likely result in some conflicts, skirmishes, or all-out wars, for control of what food supplies exist too. 

This could conceivably get so bad that other nuclear nations would be willing to use their own arsenals to secure resources or their own needs.

This would be the "worst of all worlds" scenario, as, while most human beings will not be wiped out by the nukes, many would suffer from lack of food and water, as well as the suffering that comes with the prolonged conflict between competing nations. Severe human rights violations would likely be carried out too. 

While global nuclear war is not very likely, according to most experts, so long as nuclear weapons exist, the chances are not zero. Will it become a likely scenario in the future? 

That's is anyone's guess, but let's hope none of us ever witness such a thing. If it does, pray you are vaporized within seconds, you don't want to be around afterward!