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12HISTORICAL SCIENCES
ABOUT THE HISTORY AND MODELING OF NUCLEAR WINTER
Tarko A.M.
Doctor of Physical and Mathematical Sciences, Professor of Mathematical Cybernetics, Chief Researcher of the Federal Research Center «Computer Science and Control»
of the Russian Academy of Sciences https://doi.org/10.5281/zenodo.7377209
Abstract
Forecasts of a nuclear winter that can result from a large-scale nuclear war were obtained simultaneously and independently by scientists of the USSR and the USA in 1983-1985. The history of the development, forecasts, climatic and some of its environmental consequences are described. The main active factor causing a nuclear winter is the powerful fires that have arisen as a result of the bombing of large cities, which have turned into "fire tornadoes". The resulting soot and dust block the solar radiation. According to climatic models the magnitude of the temperature drop at different points of the earth's surface ranges from 5 to 50 degrees. The country that starts a nuclear war will inevitably die from its own or someone else's nuclear strikes. Vegetation and wildlife will die depending on what period of the year the nuclear conflict occurs.
Keywords: Nuclear winter forecasts, mathematical models of global climate and biosphere processes.
"...That same summer there was a sign in heaven... At the same time there was a drought, the land and swamps were burning; the same summer the haze became 6 weeks, the sun was not seen, and the fish in the water died, and the birds fell to the ground, could not fly..."
The Sofia First Chronicle, 1431
Introduction
Almost 40 years ago, in 1983-1985, simultaneously and independently, scientists of the USSR and the USA made predictions of a nuclear winter. These forecasts were of great scientific and political importance. They proved that, firstly, that the world can be easily destroyed, and it will be a global catastrophe for both the Earth and the entire civilization, secondly, a country that starts a nuclear war will inevitably die from its own or someone else's nuclear strikes, thirdly, peace can and should be preserved, and this is really achievable, and fourthly, the presence of a large number of nuclear weapons in the two strongest nuclear countries until recently was not only a factor of aggression, but also a deterrent, providing humanity with a life without major world wars.
The work of two collectives in the USSR and the USA helped humanity in solving scientific, political and, in a good sense of the word, propaganda tasks.
After the appearance of nuclear winter forecasts in developed countries, information about it spread rapidly: newspapers were full of information and photos of participants in the work on nuclear winter, scientific and popular books understandable to the people were published. The consciousness of the imminent collapse of the world as a result of a nuclear war has penetrated not only into the hearts of scientists and specialists, but also almost all people in the developed world. Unfortunately, in the USSR there were only brief notes in the central newspapers based on materials from Western
sources, several scientific articles and two scientific books [4, 9]. Knowledge about the nuclear winter in the USSR was spread only in the scientific community. At the same time, prominent figures of the states of developed countries addressed the peoples with statements about the nuclear winter and its inadmissibility, and the mass media brought it to the entire population. In the USSR, this did not happen at all. Not a single popular book or pamphlet was published either during the USSR or in modern Russia. They did not know anything in the USSR, and to this day Russian schoolchildren do not know about it.
The forecasts of the nuclear winter, which have become famous, were obtained simultaneously and independently by scientists of the USSR and the USA. In the USSR, the work was performed at the Computing Center of the USSR Academy of Sciences. This was able to happen due to the fact that a few years before, academician N.N. Moiseev opened two divisions in it for mathematical modeling of global climatic and global ecological processes. If the nuclear winter works had been carried out only in the USA, there is no doubt that they would not have received a grandiose global resonance. At that time, only in the Computing Center of the USSR Academy of Sciences there were models equal in complexity and implementation on a computer, capable of working on an equal footing with US models.
Soon after the climatic calculations carried out by V.V. Alexandrov in the USSR, many scientific papers appeared on the climatic consequences of nuclear war. However, all forecasts were made on point models, which in terms of detail and significance did not go to any account with the forecasts made in the USSR and the USA on the most complex three-dimensional models then and now.
It is very important for science that the efforts of free scientists of the USSR and the USA gave what special services in both countries could not get, designed
to provide governments with the necessary knowledge, it was their omission.
Many years have passed since the discovery of the nuclear winter effect. At the same time, the danger of a large-scale nuclear war has not decreased. The probability of a limited nuclear war has increased many times. New types of weapons, new strategies and tactics and methods of warfare have appeared. To this we need to add new ways of waging war.
At the beginning of the XXI century, a new powerful type of war appeared - hybrid warfare. Its origins can be found in the wars of ancient Greece. This is the seizure and subjugation of a certain territory using military, hidden military and non-military means.
However, all that has been said does not in any way deny the possibility of the emergence of new wars using nuclear weapons, including large-scale nuclear war. We must not forget what a nuclear winter is and what its horrific consequences may be. To do this, the author writes this article.
The breakthrough in science made by two groups of scientists in 80th reminds us that once in the two strongest countries of the world there was a relative parity not only in offensive weapons, but also in the level of fundamental science and its applied results, which were the results of the simulation of nuclear winter.
History
In 1982 P.J. Crutzen and J.W. Birks [5] drew attention to the fact that in World War II, as a result of carpet bombing by American aircraft of the German cities of Hamburg, Dresden, Kassel and Darmstadt, large-scale fires occurred, in which large updrafts formed -"fire storms"1. They put forward the idea that as a result of nuclear bombing of large cities, a certain critical mass of fires that have arisen can be exceeded, and then they will become gigantic, everything will burn2, giant masses of smoke and soot will fly high into the atmosphere, which, spreading over vast distances, will block solar radiation, and the temperature of the atmosphere will decrease significantly. They called this effect "nuclear winter".
After that, at the beginning of 1983, a group of major climate scientists gathered together, they agreed on a joint scenario determining how many fires products will be sprayed in the atmosphere, to what height, what particle sizes, etc. Among them was my colleague, an employee of the USSR Academy of Sciences Vladimir Alexandrov, By the autumn the calculations were completed, and it turned out that the results roughly coincided - the temperature drop was predicted to be about 20-50 degrees, which shocked everyone. Thus began the world-famous work on predicting a nuclear winter.
The fact that there was one Soviet scientist among American scientists was not an accident. The possibility of such cooperation was achieved as a result of the initiative of Academician Nikita N. Moiseev. As already mentioned, in the late 70s, he founded two divisions at the Computing Center of the USSR Academy of Sciences for the study and modeling of global climatic and biospheric processes. By the beginning of the 80s, V.V. Alexandrov developed a mathematical model of the Earth's climate of the most complex type - a model of the general circulation of the atmosphere and the ocean, which allows calculating climate changes on the entire surface of the Earth and at different altitudes [2]. The model took into account the processes taking into account the real grid of geographical coordinates, including the outlines of continents, the rotation of the Earth, multilayer air flows in the atmosphere and water in the ocean at different depths. The decision curves obtained on such models are quasi-stochastic - these are not deterministic smooth lines like the flight of an artillery shell, but "dancing" curves resembling changes in meteorological parameters, for the analysis of which special procedures are required. Models of this type require the most powerful and resource-intensive computers.
By the same time Alexander M. Tarko had developed an ecological model - a model of the biogeochem-ical cycle of carbon dioxide in the biosphere - also with spatial partitioning [10]. Both models were the only ones in the country on which long-term global forecasts could be calculated, taking into account the spatial distribution of land and ocean.
In September 1983, N.N. Moiseev, V.V. Alexandrov and A.M. Tarko attended the symposium "Coevo-lution of Man and the Biosphere" held in Helsinki by the Institut de la Vie, a well-known scientific organization with headquarters in Paris (France). This symposium brought together major experts in the field of problems of the future of humanity and the biosphere -economists, ecologists, philosophers, mathematicians -specialists from the USA, Canada, France, Sweden, Finland, the USSR. Before the start of the symposium, V.V. Alexandrov showed N.N. Moiseev a piece of paper with a graph of the temperature drop during the nuclear winter, he was shocked. At this symposium, his first speech by V.V. Alexandrov on the results of the nuclear winter took place. It made an unexpectedly strong impression on the participants. Everyone was amazed. So, after V.V. Alexandrov's speech, academician von Richt, a philosopher and an elder of Finnish scientists, an elderly man, said to A.M. Tarko: "I went through the whole war, but never been so scared".
1 Werner Mende told the author of this article that when a boy he was in Dresden and saw large suitcases flying into the sky
during a severe fire after a powerful bombing
2 This provision was confirmed on September 11, 2001 in New York, when terrorist aggression was committed, and as a result of a strong secondary fire, even steel melted, as a result, two skyscrapers were completely destroyed.
The first speech of V. V. Alexandrov with a report on the nuclear winter (Helsinki, Symposium of the Institut de la Vie "Coevolution of Man and the Biosphere", 1983)
N.N. Moiseev (left), V. V. Alexandrov (center) and A.M. Tarko (right) in Helsinki at a reception during the symposium of the Institut de la Vie "Coevolution of Man and the Biosphere" in 1983.
S. Landry (Canada) (left), N.N. Moiseev (center) and A.M. Tarko (right), in Helsinki during a break at the symposium of the Institut de la Vie "Coevolution of Man and the Biosphere" in 1983.
The organization of work on nuclear winter was taken over by the organization SCOPE - the Scientific Committee on Environmental Problems. It gave scientists the opportunity to get together at several workshops, to attract the missing specialists. Two volumes "The Consequences of Nuclear War" were published and a popular book. The first volume was devoted to climatic consequences [6], the second - ecological and agricultural [7]. Both volumes were soon translated into Russian.
In the USSR two books were published - in the first [9] one chapter contained the results of V.V. Ale-xandrov on modeling nuclear winter (his doctoral dissertation), in the second [4] the results of ecological, demographic and agricultural forecasts of nuclear winter, carried out under the guidance of Yu.M. Svirezhev and A.M. Tarko, were published. There was also an issue of the Computing Center of the USSR Academy of
Sciences, in which there was an article by V.V. Ale-ksanrov and G.L. Stenchikov [3], with slightly later calculations of the climatic consequences of a nuclear winter.
The work of scientists in spreading knowledge about the nuclear winter was not limited to activities in the SCOPE. An unusually famous figure was the Soviet scientist Vladimir Alexandrov. He was invited to many different conferences, symposiums and other events. Thus, the Pontifical Academy of Sciences invited scientists from the USSR and the USA to a joint meeting, which was attended by Academician E.P. Velikhov and V.V. Alexandrov. The author of this article remembers well the photos in which all the scientists present were filmed, a photo of a personal meeting between Pope John Paul II and V.V. Alexandrov.
Pope John Paul II and V. V. Alexandrov after his speech at the Pontifical Academy of Sciences during the stay of the delegation of the USSR Academy of Sciences there, 1984
Another important event was the visit of Academician N.N. Moiseev and V.V. Alexandrov to Washington, DC (USA) at the invitation of Senator Edward Kennedy and speech of V.V. Alexandrov in the US Senate with a report on nuclear winter. After the speech, Edward Kennedy stressed that according to calculations, the country that starts a nuclear war will inevitably die from its own or someone else's nuclear strikes — it will not matter. He also noted the importance of the fact that calculations of nuclear winter were obtained independently by American and Russian scientists, which gives more confidence to such results.
Unfortunately, in the midst of the events, Vladimir Alexandrov disappeared without a trace, being invited to a conference of mayors of non-nuclear cities in Spain. It is known that he flew to Madrid from Cordoba, where the conference was held, feeling unwell. The staff of the Soviet embassy put him in a hotel, he left it for a walk and ... disappeared. His doctoral dissertation was to be defended in 20 days. The international measures taken to find him have not yet led to anything.
Climatic consequences of a large-scale nuclear war (nuclear winter)
When analyzing the possible climatic consequences of a large-scale nuclear war, the researchers proceeded from the scenario published in the double issue of the journal Ambio [1]. The authors of the scenario assumed that a nuclear conflict would occur between the two main warring parties and that nuclear strikes would be inflicted almost instantly. Less than half of the total nuclear arsenal of the USSR and the USA will be used in the war. The total stock of nuclear charges consumed on both sides will amount to 5,742 Mt. The whole of Europe, the USSR, North America
and the Far East region, including Japan and South Korea, will be hit. It is assumed that strikes will also be carried out on countries not directly involved in the war, with the aim of undermining their economic potential and reducing their importance in the post-war situation.
Large cities are the primary targets approved by strategic planners in nuclear attacks on industrial facilities that make up the most important part of the enemy's defense and economic potential.
The fires that arise in cities ("primary fires") cause extensive "secondary" fires. Then many pockets of flame of those and other fires will unite into one powerful hearth, and a "fire tornado" will form, capable of destroying an entire city (as happened as a result of the bombing of Dresden and Hamburg at the end of World War II).
The intense release of thermal energy in the center of such a giant fire lifts up huge masses of air, creating winds of hurricane force at the surface of the earth, which supply more and more portions of oxygen to the fire. It is as a result of the "fire tornado" that smoke, dust and soot rising up to the stratosphere form a black cloud that almost completely covers the sunlight, the "nuclear night" comes.
Calculations of the amount of aerosol formed after nuclear "fires of civilization" are made based on the average value of 4 g of combustible material per 1 cm2 of the surface, although in a number of large modern cities, such as New York or London, this value reaches 40 g/cm2 (wood, plastics, asphalt, fuel, etc.) According to the most careful calculations, during a nuclear conflict (according to the average, so-called baseline scenario), about 200 million tons of aerosol is formed, 30% of which is elemental carbon that strongly absorbs sunlight. A vast area between 30°S and 60°S in case of fires
and the release of aerosol in the quantities indicated above, it will be almost completely deprived of sunlight for at least several weeks.
Calculations show that during the stay of the aerosol in the atmosphere, the black layer of soot will be intensively heated by the sun's rays and rise up together with the air masses heated from it. Convective processes (i.e., the mode of evaporation of moisture and precipitation) will be significantly suppressed, precipitation will decrease, and with them the leaching of aerosol. All this will lead to a significant lengthening of the duration of the nuclear winter.
The aerosol, like a smoky veil, will spread across the Northern Hemisphere in two weeks, and from the Northern Hemisphere to the Southern hemisphere in two months. In whatever country the bombs explode, everything will get mixed up. The Sun's rays will not reach the Earth's surface, and the air temperature in different places will drop by 10 - 30° C. After a year, this aerosol should still settle on the surface. This conclusion was reached by Vladimir Alexandrov and his colleagues (Fig. 1).
180 W Q 180 £
Fig. 1 Change in air temperature at the underlying surface for a nuclear war scenario with a total capacity of
10,000 Mt 40 days after the start of the war [9]
Note that there will also be a significant decrease in atmospheric temperature in the Southern Hemisphere. Calculations show that dust and smoke and darkness will spread to the tropics and most of the Southern Hemisphere. Thus, even non-belligerent countries, including those located far from the conflict area, will experience its disastrous impact. Countries such as India, Brazil, Nigeria or Indonesia can be destroyed as a result of a nuclear war, despite the fact that not a single warhead will explode on their territory. A nuclear winter means a significant increase in the scale of suffering for humanity, including nations and regions not directly involved in a nuclear war.
These calculations of the nuclear winter were obtained on the basis of the basic scenario of a large-scale
nuclear war. However, another calculation was also carried out. It is based on a scenario according to which "only" 100 Mt of nuclear arsenal will be used in the war (so much at that time could be carried and quickly released by an American submarine), but on the condition that all charges will be directed at major cities. At the same time, it turned out that a nuclear winter of almost the same strength would also occur (Fig. 2). However, it will last a shorter time - about two to three months -but this is enough for almost the same results for the destruction of a significant percentage of life on Earth. Here, the insensitivity of the effect of nuclear winter on the number of nuclear weapons used was revealed, not only large-scale, but also up to a certain limit and limited nuclear war.
A o mc isow
Fig. 2. Map of the air temperature drop at the Earth's surface a month after a nuclear war with a capacity of
10,000Mt (A) and 100Mt (B) [9]
Ecological consequences of nuclear winter
Following the climate forecasts, scientists from the USA and the USSR calculated ecological and demographic ones. The assessment of the environmental consequences of a large-scale nuclear war was carried out in the USSR on the basis of V.V. Alexandrov's climate calculations, it was made by a group of scientists of the Computing Center of the USSR Academy of Sciences and several other organizations under the leadership of Yu.M. Svirezhev and A.M. Tarko.
Here are the results of the effects of factors of temperature drop and reduced illumination on the flora and fauna [4]. These results were obtained by A.M. Tarko together with N.F. Pisarenko and A.D. Armand. To estimate the drop in temperature and illumination during a nuclear winter, the results of calculations on the climatic model of the Computing Center of the USSR Academy of Sciences were used (Fig. 1).
The ecological impact of the factors "nuclear winter" and "nuclear night" on ecosystems is the most difficult to assess factor of nuclear war. If the effect of such a factor as nuclear radiation can be assessed by the results of already conducted nuclear weapons tests, then nuclear winter has not been encountered in the history of the biosphere. We will first look at some general aspects of the effects of low temperatures and low light on ecosystems, and then use the available information on the effects of factors close to the factors of nuclear winter to obtain estimates.
Almost complete blocking of solar radiation by nuclear aerosol leads to a rapid drop in the surface temperature of continents in the Northern Hemisphere. Within 15 days, the temperature of the lower layers of the air drops by 10-50° C, and then begins to grow slowly. In the tropics, the temperature drops to 0°C in a month. In three months, a wave of pollution reaches Antarctica. The long-term temperature drop in the Southern Hemisphere averages 5-8°C. The cooling of the southern oceans changes the dynamics of the nuclear winter and increases the duration of cooling. Three months after the start of the nuclear conflict, the upper layers of the air over Antarctica will be clouded. Following the clouds of soot, a nuclear winter will spread to the continents of the Southern Hemisphere. Up to 30°S the air temperature over the continents will drop by 1-4°C. In a year, all climatic factors will approach the norm.
There are two factors of the effect of nuclear winter on vegetation. The first is a cold snap, the second is a decrease in illumination. Consider the effect of both factors. Plants can be divided into cold-sensitive and frost-sensitive. Plants sensitive to cold die or get damaged at temperatures above 0°C, and those sensitive to frost — below 0°C. The primary cause of the death of plants sensitive to cold is the transition of cell membranes from a predominantly liquid crystal state to a gel state due to the solidification of membrane lipids. The cause of death of plants sensitive to frost is the formation of ice inside the cells or the formation of ice in the intercellular space.
Cold resistance and frost resistance are not permanent properties of plants, but in accordance with their
genotype are formed in the process of ontogenesis under the influence of environmental conditions. Frost resistance changes dramatically throughout the year. It is minimal in summer and maximal in winter.
To become frost-resistant, according to I.I. Tu-manov [11], plants must undergo three stages of preparation sequentially: enter a state of physiological rest, pass the first and then the second phase of hardening. High frost resistance in plants is not formed immediately, it increases in stages: first when entering the dormant period after the end of the growing season, then during hardening and, finally, as a result of a slow and gradual increase in frost in the second phase of hardening. Maximum frost resistance is achieved in the most severe time of the year.
Each of these stages is preparatory for passing the next one. If any link in such a long (several months) preparation of plants for winter falls out or passes unsatisfactorily, then the plant will not be able to acquire the necessary frost resistance. For example, due to the summer drought, fruit plantations often do not have time to finish the growing season normally. Therefore, they do not have time to prepare for winter and die in such frosts, which, under favorable summer conditions, they can withstand without difficulty. Siberian fir withstands frosts up to -60°C near the cold pole in Siberia, forming extensive forests there, and freezes on the banks of the Rhine in the warm climate of Central Europe.
In the process of evolution, plants have adapted to the change of seasons and the associated decrease in air temperature or the onset of the dry season. In perennial plants, during the transition to a dormant state, growth almost stops and intensive accumulation of sugars begins, and then photosynthesis completely or almost completely stops, the leaves of deciduous plants fall off. During the hardening process, protective substances (cryoprotectors) in the form of sugars, water-soluble proteins, organic acids actively accumulate in plant cells, as well as the unsaturation of lipids increases [8], complex conformational changes of proteins occur. In woody plants, a significant (up to 4050%) decrease in the water content in the trunk was noted. All these rearrangements contribute to the transfer of low temperatures by plants.
For the transition of plants to a dormant state, a sufficient level of illumination is necessary at the initial stage of this process. All processes associated with the transition to a state of rest require certain energy costs. The source of this energy is assimilates formed during photosynthesis. The transition to a state of rest begins with the fact that the growth of the plant stops, and assimilates begin to accumulate in the form of sugars — mobile energy sources. Therefore, if the illumination at the beginning of the transition to a dormant state is low, then the plants will not receive enough energy for the necessary rearrangements. Under normal conditions, by the end of the growing season, the illumination decreases somewhat, but it is sufficient to transition to a state of rest.
With a significant decrease in illumination (by 20100 times compared to the value of photosynthesis saturation illumination), the energy intake decreases so
much that it does not cover the cost of respiration, and pure photosynthesis becomes zero. This so-called compensation intensity of illumination Ik is different for different plant species and the lower the air temperature. If the illumination falls below the Ik value, the plant may die.
Plants of the same species in the same phytoceno-sis tolerate the effects of low temperatures and light conditions in different ways. Weakened trees, old and very young tolerate the effects of these factors worse than others. Therefore, if there is a low temperature or illumination, which does not reach the limit values for the death of most plants, then some of the plants will still die. The percentage of plant death will be greater the closer to the limit values of temperature or illumination.
We will consider two extreme cases. The first is when a nuclear conflict occurs in July, the second is in January. The absolute values of the air temperature at the underlying surface for different parts of the Earth are obtained by subtracting the calculated value of the temperature drop from the standard average summer values for the case if a nuclear war began in the summer. Similarly, if it started in winter.
July is the warmest month in the Northern Hemisphere. According to our calculations, 15 days after the spread of pollution in the Northern Hemisphere, the air temperature at the land surface in almost the entire Northern Hemisphere will become below zero. The zero isotherm will pass through the equator. On the 9th day after the spread of pollution, the illumination north of 18°N will be less than 3.6 10-5 W/m2. This illumination is (3-80) 104 times less than the compensation illumination of Ik plants measured at normal temperature. It can be assumed that the supply of energy to plants will stop. Will the plants have time to adapt to low temperatures? It can be argued that there is not.
For plants of the northern and middle bands, under normal conditions of the end of the growing season, the transition time to a dormant state is more than two weeks. The main factor causing the beginning of the transition to a state of rest is a reduction in the length of daylight. To a lesser extent, the decrease in air temperature affects. From the beginning of the action of this factor to the beginning of the transition to the sugar storage mode, at least 3-5 days pass. If during this time, in the conditions of the beginning nuclear winter, the mechanism of transition to a dormant state is triggered,
then due to the rapid and strong decrease in illumination, plants will not have time to accumulate a sufficient amount of assimilates (no more than 10% of the required will be accumulated), and the transition to a dormant state will not occur. The subsequent effect of negative low temperatures for more than three months will inevitably lead to the death of plants.
Similarly, subtropical plants will not have time to go into a state of rest and will die in conditions of low temperatures and lack of light. Plants will freeze out, in which the transition to a dormant state occurs due to the onset of the dry period. In tropical moist forests, the illumination will be higher than compensation (70 W/m2 on the 40th day and 50 W/m2 on the 99th day after the start of a nuclear war), but since the plants of these forests do not have the ability to go into a state of rest and harden, they will die from the effects of low temperatures.
In the Southern hemisphere in July - winter, the temperature drop will be (1-4)°C for the latitudinal zone (0-12)°S, and the illumination is 30% of the original. In such conditions, not all plants will withstand a prolonged decrease in temperature, and most importantly, illumination. In this case, the above-mentioned effect of predominant damage to weakened, old and young trees will manifest itself. This zone is mainly occupied by tropical forests. About 60% of the plants of the upper tier of these forests are in a climax state, they have no growth and photosynthesis is equal to respiration. A decrease in illumination will lead to an energy deficit that these plants will not be able to compensate for. Therefore, these plants will die.
Instead of dead plants, shade-tolerant plants will benefit. These plants will hinder the growth of young light-loving plants under their canopy. Young light-loving plants will die due to shading by shade-tolerant ones. Considering the ratio of light-loving and shade-tolerant plants in tropical forests, we will get that about 50% of plants will die in general.
In the latitudinal zone south of 12°C. The decrease in temperature will not exceed 3°, and the illumination will not exceed 4%. This will not cause significant damage to the plants.
Thus, if a nuclear war starts in July, the entire vegetation of the Northern Hemisphere will die, and in the Southern hemisphere it will partially die (Fig. 3).
Fig. 3. The degree ofplant death under the influence of nuclear winter factors in the event that a nuclear conflict
occurs in July
The death of animals in the Northern Hemisphere in these circumstances will be determined by the lack of food and the difficulty of finding it in the conditions of a nuclear night. In tropical and subtropical areas, cold will be an important factor. Many species of mammals and all birds will die, part of reptiles will be able to survive.
January is the coldest month in the Northern Hemisphere. The plants of the northern and middle bands are at rest at this time. Therefore, their tolerance of nuclear winter will be determined by the amount of frost.
The greatest temperature drop will be in the latitude band 12-36°N — up to 54°C. The absolute temperature values in this zone will be (-6)-(-42)°C. The
Maximum frost resistance of trees
temperature drop in the Far North in the band 48-62°N will be 11-38°C. In this case, the absolute temperature values will be (-15)-(-72)°C.
Let's consider the effect of nuclear winter in this case separately on different types of vegetation. We will adhere to the biogeographic principle of consideration.
1. Tundra, forest tundra, taiga forests, broad-leaved forests. To assess the ability of these plants to tolerate frost, the distributions of individual tree species and the average absolute minimum temperatures were compared. The analysis of these data allowed us to estimate the minimum temperatures that trees can tolerate in winter (Table 1).
Table 1.
(the duration of frost is 1 month)_
Teees Frost resistance in winter, ^ Trees Trees frost resistance in winter, °C
Beech -25 Pine tree -65
Oak -40 Fir -65
Birch -55 Cedar -55
Spruce -65 Larch -65
It turned out that due to different temperature val- plants in Europe, Siberia and North America will be ues in a normal winter and different temperature drops different. Data on the death of plants in three regions during a nuclear winter, the degree of death of the same are presented in Table 2.
Table 2.
Vegetation loss in some types of plant communities (nuclear war begins in January)
Vegetation type Death of vegetation, %
Europe Siberia North America
Arctic deserts, tundra 25 10 25
Forest tundra, North taiga forests 25 10 50
Middle Taiga, southern Taiga forests 50 25 75
Broad-leaved-coniferous, broad-leaved subtropical forests 100 100 100
Steppes 90 90 90
On the map of types of plant communities (Fig. 4), the corresponding areas occupied by those indicated in the table 2 communities were marked.
Fig. 4. The degree ofplant death under the influence of nuclear winter factors in case a nuclear conflict occurs
in January
2. Steppes. Cold weather in the steppe zone will lead to the death of the aboveground part of plants and to the almost complete freezing of their root system. The frost resistance of the aboveground part of herbaceous plants in the steppe zone is (-11)-(-20)°C, and the temperature in the nuclear winter here will be (-23)-(-30)°C. A number of bulbous plants may survive for several months. About 90% of plants will die.
3. High-altitude deserts, alpine, subalpine meadows. The type of mountain vegetation is adapted to tolerate significant low temperatures. Therefore, plants will partially be able to withstand a nuclear winter. About 75% of plants will die. In the alpine and subalpine meadows of Tibet, the temperature drop will be more than 50°C, and with a strong drop in illumination, their vegetation will die almost completely.
4. Tropical and subtropical forests, savan-nas.The tolerance of the factors of nuclear winter by this vegetation will be the same as in the case when a nuclear conflict occurs in July. Therefore, the death of these plant species will also be complete.
5. Vegetation of the Southern hemisphere. In January, it is summer in the Southern Hemisphere. The tolerance of the factors of nuclear winter by plants in the equatorial zone will differ slightly from the tolerance if a nuclear war begins in July. This is due to the fact that in the tropical zone the temperature difference between winter and summer is small.
In the more southern part of the hemisphere, the change in temperature and illumination will be weak and the influence of nuclear winter factors will be insignificant.
6. The death of agroecosystems. In this situation, we can talk about the possibility of survival of winter crops. All other wintering agrocenoses (fruit plants, etc.), as shown by the results of comparing frost resistance and absolute temperature values in the nuclear winter, will die. The frost resistance of winter rye is (-30)°C, and wheat, depending on the variety (-16)-(-26)°C. In the nuclear winter, temperatures in the winter crops zone will be (-22)-(-40)°C. Therefore, a small
part (about 10%) of winter crops can withstand frosts. However, the probability of their survival after the end of the nuclear winter (due to the action of other factors of nuclear war) is almost zero.
7. Animals. If a nuclear war begins in January, the death of animals in the temperate and high latitudes of the Northern Hemisphere will be determined by severe cold and the difficulty in low light to find enough food to maintain the increased energy needs in these conditions. The death of mammals and birds in these conditions will be complete. The death of animals in the tropical zone will be approximately the same as in the case of a nuclear war that began in July.
8. The ocean. The ocean is the most conservative block of the biosphere. Due to its size, it dampens many local fluctuations of climatic and biogeochemical factors. Nuclear winter is likely to have the greatest impact on its ecosystems. However, during the nuclear winter, the surface layer of the ocean will cool by 1.2° according to calculations [9]. Therefore, the main factor affecting the biota of the ocean will be a drop in illumination and the complete cessation of photosynthesis. There will be a significant decrease in the amount of phytoplankton, but it will not be completely destroyed, since many species will go into a dormant state and survive the nuclear winter. After its completion, the amount of phytoplankton will recover within a few years. The death of many fish species is possible, mainly due to the lack of sufficient food and the inability to find it due to low light. However, the complete disintegration of the trophic pyramid will not occur, since bacterioplankton and dissolved organic matter will remain intact in the food chains.
Long-term climatic consequences of nuclear winter
After the end of the nuclear winter intensity of the cycle of chemical elements (carbon, nitrogen, etc.), as well as the total amount of matter involved in the cycle, will decrease. As a result, the amount of CO2 in the atmosphere will increase, the accumulation of nutrients in reservoirs will increase.
Due to fires, a significant amount of CO2 will enter the atmosphere. The death of trees as a result of climatic and radiation stresses will lead (due to the decomposition of the organic matter of wood) to an additional flow of CO2 into the atmosphere. As a result of a decrease in the productivity of land plants, the amount of humus will also decrease. Consequently, the soil will become a source of atmospheric CO2. The absorption of excess atmospheric CO2 will be determined by the ocean for a long time.
Let's make an estimate of the change in CO2 in the atmosphere and the average global temperature, based on the following scenario. Assuming that 20% of the forests of the Northern Hemisphere will burn during
fires, we get that the amount of CO2 in the atmosphere will almost instantly increase by 15%. Then, during the nuclear winter, all the forests of the Northern Hemisphere and the tropics will die. The corresponding areas will be overgrown with grass and shrubby vegetation within five years. The processes of decomposition of dead organic matter, litter and humus after a nuclear winter will be fully restored in three years. The transparency of the atmosphere will be restored immediately after the end of the nuclear winter.
According to this scenario, using the model [4], the dynamics of changes in atmospheric CO2 and the average global temperature were calculated (Fig. 5).
Fig. 5. Changes of CO2 concentration in the atmosphere (in units relative to the current concentration) and temperature after a large-scale nuclear war. The year from the end of the nuclear war was marked as zero
The main flow of carbon into the atmosphere three years after the war will be determined by the decomposition of dead organic matter that died during the nuclear winter. After 30 years, the amount of CO2 in the atmosphere will increase by 1.6 times, and the temperature (due to the greenhouse effect) will rise by 1.3° C. then a slow decline will begin, which will last up to 100-150 years.
The general conclusion concerning biogeochemi-cal cycles is that the destruction of forests and the replacement of forest ecosystems with grass and swamp ecosystems dramatically reduce the stability of the biosphere as a whole and its ability to dampen climatic variations. This is due to the fact that forest ecosystems most effectively regulate the global carbon cycle and the closely related global atmospheric temperature. Therefore, the climate will become less stable.
References:
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