Science of Environmental Effects of Nuclear War

The only atomic bombs to ever be used outside of testing were those used by the United States in Hiroshima and Nagasaki to end the Second World War. These blasts exploded with the force of about 15 kilotons and 21 kilotons of TNT respectively (World Nuclear Association, 2016). The total nuclear arsenal in the world today includes more than 14,000 nuclear weapons, many of which are even more deadly than those (Kristensen & Norris, 2018). This could destroy the world multiple times over and yet we never really consider what would happen in the long run if these weapons were to be used. Politicians and policy-makers like to talk about the size of a nuclear blast and the initial consequences that would result from their use, such as severe radiation poisoning and black snow, but they do not consider that nuclear war could have lasting consequences on the environment far beyond the area directly affected by the blast. The goal of this paper is to discuss the scientific research that has gone into understanding what would happen to the environment and climate in the event of a nuclear war.

In the eighties, a lot of research was done that looked into the lasting effects of nuclear war on the environment and people of the world. However, with the Cold War underway, the government did work to undermine scientists and research that implied that nuclear weapons would cause huge problems for the environment beyond the initial blast, coining the term “nuclear autumn” to combat the research that described the possibility of a “nuclear winter” following a nuclear war (Starr, 2009). This slowed research and it also helped to keep the public away from information that could lead to unrest if widely known.

Unfortunately, the short-term effects of nuclear warfare have been observed through the survivors of the bombs that were dropped on Hiroshima and Nagasaki. The radiation poisoning, cancer, intense burns, and all the other horrors of nuclear war were enough to keep the United States and the Union of Soviet Socialist Republics (USSR) away from actual conflict during the Cold War, but still today policy-makers often overlook the true, long-term, climate, and environmental horrors that would become reality in the event of an extended nuclear war be it in that politician’s country of origin or not.

Two main scenarios have been extensively considered in research and simulations. When these two scenarios were first proposed they were somewhat topical, now they are used to keep the research and data consistent. The first is considered a small-scale nuclear war between India and Pakistan (Toon et al., 2007). These countries were chosen only because they had access to some of the smaller nuclear arsenals in the world with the total between them being about 100 atomic weapons. This 100, each approximately on the scale of the weapon used in Hiroshima, weapon war made for a decent baseline scenario which could be used to compare other smaller- or larger-scaled wars. The second, larger scenario is a full-scale strategic war between the United States and Russia. This scenario is considered in the research to be one of the worst possible scenarios and would most certainly result in the deaths of a majority of the human population on Earth (Robock et al., 2007) and the changing of life on this planet as we know it. Additionally, any nuclear war, regardless of size, would kick up huge amounts off soot into the upper atmosphere where it could, especially in larger scenarios, counteract the greenhouse effect and create a period of rapid cooling known as nuclear winter.

It is generally thought that a smaller nuclear force would target the largest cities possible as that would be most likely to do the most damage. This tactic would lead to huge firestorms spreading across urban and industrial spaces. A firestorm is when multiple fires within an area that contains a lot of fuel coalesce into one massive fire which heats the air and can cause heavy winds, further spreading the fire. This would kick an astronomical amount of soot into the air all at the same time on the scale of a couple million tons (Robock & Toon, 2012). All this soot would be able to make it into the upper stratosphere where it would reflect and absorb sunlight, keeping that light from reaching the surface of the Earth (Robock & Toon, 2012). This could block sunlight on a regional level, produce a regional state of cooling temperatures, and potentially decrease the average yearly rainfall amounts. However, this would not be certain to affect the rest of the world in any large way. This is because the soot clouds would not be large enough to cover areas outside of the region of the war.

Newer, more accurate models have found that the original estimates of global cooling as a result of nuclear war were actually quite low. The old models predicted that the global average temperatures would decrease quite a bit initially and that the soot would remain in the upper atmosphere for a couple years at most. The newer simulations utilize the NASA Goddard Institute for Space Studies climate model of the entire troposphere, stratosphere, and mesosphere, and they predict that the Earth’s average temperature would actually decrease further than initially estimated and that the soot would remain in the upper stratosphere for significantly longer than predicted. The new estimates are that the average global temperature would decrease by about 1.25 degrees Celsius on average for the first few years and that the soot would hang around in the upper stratosphere for at least a decade, with temperatures still about .5 degrees Celsius below average at the end of that decade. These decrease temperatures would be most noticeable in the areas directly affected by the nuclear war, but they would be significant enough to affect the global averages. While the global temperature does not appear to decrease very drastically, most of the cooling would be regional and would affect the Northern hemisphere in particular, shortening the growing season for some crops by up to thirty days. This would cause crops to fail to reach maturity and many of the world’s food producing crops, such as grains and fruits, would not yield enough if any at all (Harwell & Harwell, 1986). Not only this, but the average global precipitation could be reduced by approximately 10% (Starr, 2009) further harming crops and food production. The effects of these changes in global climate, and particularly in the climate of the northern hemisphere, are simple to see from this data. Many crops would fail in the first few years and food would become very scarce; without even considering the other issues, the food shortages alone would cause many deaths after the end of the war.

If, however, a larger catastrophe was to occur, a strategic war between two or more very large nuclear arsenals, the effects could be even more devastating for the entire world, not just for the regions directly impacted. Another simulation was done by Robock, Oman, and Stenchikov (2007) to test what would happen if approximately one third of the world’s nuclear weapons, about 4,000 weapons, were to be detonated in this type of conflict. Once again using the NASA Goddard Institute for Space Studies climate model, it was estimated that this kind of war would produce 180 million tons of soot and would result in 70% of the sunlight being blocked from the surface of the northern hemisphere and 35% from the southern hemisphere. So much of the sunlight would be blocked out that many people would experience multiple days of darkness in which even midday appears as dark as a moonlit night (Robock & Toon, 2012). This could cause the average global temperatures to decrease rapidly by up to eight degrees Celsius and after a decade the temperatures could still be four degrees below the normal as the soot layer would still linger in the upper stratosphere. The cooling caused by the soot would be potentially worse than the cooling in the worst part of the last Ice Age (Robock et al., 2007).

In addition to the global cooling, regional cooling in this larger war would be even more intense than just eight degrees Celsius. The central part of the United States, if attacked by a large number of nuclear weapons, could see decreased temperatures around twenty degrees and parts of Eurasia could see decreases around thirty or even thirty-five degrees Celsius (Robock et al., 2007). This cooling, in particular, is what would kill almost anyone who survived the initial nuclear blasts. Nightly temperatures could drop below freezing fairly consistently during the first one to three crop growing seasons and cause almost no fields in these areas to produce anything useful. Without these crops, many people in Europe, Asia, and North America will starve to death and other food producing livestock would die due to a lack of food. This would only further the overall food shortages.

Not only would crops fail due to the decreased temperatures and the shortened growing season, but, the crops would likely not get enough sunlight or rain, due to the soot in the stratosphere. The upper stratosphere is above where our usual weather occurs. This means that when the sun is blocked out, less evaporation will occur, and rainfall will decrease significantly. In the moderate to large war simulations, global rainfall is predicted to decrease by 45% (Starr, 2009). Without this rainfall and sunlight, regardless of freezing temperatures, crops would undoubtedly fail and livestock and humans alike would die due to a lack of access to food.

The global climate and the health of any survivors of either of these conflicts would depend on another factor, as well, and that is the ozone layer. The soot lofted into the upper parts of the atmosphere would carry particles that would rapidly destroy the ozone layer. The soot is heated to near water’s boiling point and chemical reactions causes bonds in the ozone to break. With the ozone layer significantly weakened, the Earth would be exposed to more ultraviolet radiation than most life would be able to handle. Plants have been shown to have reduced height and shoot mass when exposed to increased UV light, further reducing the survivors’ access to food. Additionally, higher levels of UV-B light have been shown to inhibit phytoplankton activity which would cause the ocean’s total food production to decrease drastically (Smith et al., 1992). This ozone depletion, and therefore the increased exposure to UV light, would last for around five years and then there would remain lesser issues for another five years. During those first five years, the UV index could reach nearly double what is considered the standard safe maximum (Mills et al., 2014).

Throughout the years, research into the full effects of nuclear war has been done, suppressed, and done again. Nuclear war, even on a small scale, would cause death beyond those initially injured in the blast due to regional cooling and soot kicked up into the atmosphere. A larger war could cause world-wide famine for a decade due to nuclear winter, decreased sunlight, and decreased rainfall. Additionally, a large war could also break down large parts of the ozone layer that protects the Earth from harmful ultraviolet radiation leading to significantly decreased ocean life, less healthy plant life, and lasting issues due to the loss of that ozone. Any nuclear war would kill many more people than just those caught in the initial blast and a larger war could change life on Earth into the distant future. Even a single nuclear blast is harmful, but an all-out war would be devastating for the environment.


Biography Image for Sarah VanHoesenI am from Ozark, MO where I attended school for 13 years and participated in the International Baccalaureate Diploma program. This May I will be receiving bachelor’s of science degrees in both physics and philosophy with a minor in mathematics. My plan after graduation is to work for a year before attending graduate school seeking a degree in biophysics. In my free time I enjoy reading fiction and swimming.