Home Potato The climate of the geological past and modern era. Summary: Climate in the past and present, and long-term forecasts. Vice-President of the Russian Academy of Sciences about the synthetic world in which a man of the XXI century lives

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The climate of the geological past and modern era. Summary: Climate in the past and present, and long-term forecasts. Vice-President of the Russian Academy of Sciences about the synthetic world in which a man of the XXI century lives

Introduction

Changes in the environment occur not only as a result of anthropogenic impact, but also under the influence of natural causes. This applies primarily to the climate. Climate fluctuations and its natural variability have always had a significant impact on the development of life on Earth, and in the last millennia, on the development of civilization. In the second half of the 20th century, it became obvious that due to anthropogenic and natural influences, the general climatic situation is changing much faster than in previous times. This circumstance has forced many scientists around the world to focus their efforts on studying the nature of climate change and their impact on the biosphere and society.

Considering the problems of global climate change, the depletion of the ozone layer in the Earth's atmosphere, the proposed measures to reduce the emissions of greenhouse and ozone-depleting gases, it is necessary to analyze the possible ratio of natural and artificial causes of deviations from the environmental crisis.

The history of the development of the Earth's climate

The development of microorganisms similar to modern blue-green algae was the beginning of the end of the regenerative atmosphere, and with it the primary climate system. This stage of evolution begins about 3 billion years ago, and possibly even earlier, which confirms the age of stromatolite deposits, which are the product of the vital activity of primary unicellular algae. Their finds in South Africa date back 2.7-2.9 billion years ago.

Noticeable amounts of free oxygen appear about 2.2 billion years ago - the atmosphere becomes oxidizing. This is evidenced by geological milestones: the appearance of sulfate sediments - gypsum, and in particular the development of the so-called red flowers - rocks formed from ancient surface sediments containing iron, which decomposed under the influence of physicochemical processes, weathering. The red flowers mark the beginning of the oxygen weathering of the rocks.

O.G. Sorokhtin recently put forward a new hypothesis, according to which, as a result of the continuous formation of the Earth's core, an excess of oxygen is released from the zone of its formation, "seeping" to the planet's surface and participating in the formation of the atmosphere. According to O.G. Sorokhtin, it was in this way that the atmosphere became oxidizing, and it is even possible that it had a certain amount of oxygen from the very beginning.

It is assumed that about 1.5 billion years ago, the oxygen content in the atmosphere reached the "Pasteur point", i.e. 1/100 of the modern. Pasteur's point signified the emergence of aerobic organisms that underwent oxidation during respiration, with the release of significantly more energy than during anaerobic fermentation. Dangerous ultraviolet radiation no longer penetrated the water deeper than 1 meter, since a very thin ozone layer still appeared in the oxygen atmosphere. The atmosphere reached 1/10 of the modern oxygen content more than 600 million years ago. The ozone shield became more powerful, and organisms spread throughout the ocean, leading to a veritable explosion of life. And soon, when the first most primitive plants came out on land, the oxygen level in the atmosphere quickly reached modern and even surpassed it. It is assumed that after this "surge" in the oxygen content, its damped oscillations continued, which, possibly, take place in our time. Since photosynthetic oxygen is closely related to the consumption of carbon dioxide by organisms, the content of the latter in the atmosphere fluctuated.

Along with the changes in the atmosphere, the ocean began to acquire other features. The ammonia contained in the water was oxidized, the forms of iron migration changed, sulfur was oxidized into sulfur oxide. Water from chloride-sulphide became chloride-carbonate-sulphate. A huge amount of oxygen was dissolved in seawater, almost 1000 times more than in the atmosphere. New dissolved salts have appeared. The mass of the ocean continued to grow, but now more slowly than in the first stages, which led to the flooding of the mid-ocean ridges, which were discovered by oceanologists only in the second half of our century.

In the following geological eras, a significant change in the Earth's climate was observed. For example, in the Triassic period of the Mesozoic era, the climate was harsh and dry, but warm enough, as a result of which deserts were greatly developed. Later, during the Jurassic and Cretaceous periods, the climate became significantly warmer, moistened and became more even. Glaciers have practically disappeared, rainforests have covered numerous areas on the continents.

The climate at the beginning of the Tertiary period of the Cenozoic was even, warm and humid. Palm trees and tree ferns grew in great numbers on all northern continents. Evergreen subtropical trees made up the bulk of the Paleocene forests. The ancestors of our trees with falling leaves were much less common.

The climate in the Eocene epoch of the Tertiary was warm. Fan-leaved and date palms continued to grow widely on the northern continents, which were covered with evergreen forests.

In the Oligocene, climatic conditions remained moderate and humid, but compared with the Eocene climate, they acquired drier and cooler features. Palm trees did not grow so abundantly on the northern continents, but evergreen forests still dominated here. Among them there are more coniferous and deciduous trees, periodically dropping their foliage. natural climate warming biosphere

At the end of the Tertiary period, the climate became colder and colder. In the Miocene time, palm trees have already disappeared in Europe. They were replaced by coniferous and deciduous trees with falling leaves. In connection with the cooling of the climate in the Miocene epoch, herbaceous plants developed intensively and the steppes became very widespread.

The Quaternary, or Anthropogenic, period - the last and shortest period in the history of the Earth - began only about 1.65 million years ago. Geologists subdivide the Quaternary system into two sections: the Pleistocene and the Holocene, the latter covering the last 10 thousand years and therefore is often called modern time.

During the short Quaternary period, there were no significant movements of the continents. However, the climate changes were enormous. Anthropogen differs from previous geological eras by a strong cooling of the climate, which left its mark on both the terrain and biological forms. The cooling process, which began at the end of the Tertiary period, continued in the anthropogen with increased intensity, reaching its maximum here. As the temperature dropped, snowfields and glaciers formed on elevated places, which did not have time to melt in summer. Under their own weight, they slid down the mountains into the valleys, and over time, vast areas of the northern and southern hemispheres were under the ice. Glaciers crept from north to south, covering Canada, the northern half of Europe and most of northern Asia with ice.

At some points, the ice crust covered over 45 million square kilometers, which accounted for up to 26% of all land, while the area of modern glaciation is about 16 million km 2, or 11% of the land. In Europe, glaciation reached southern England, Holland, Harz and the Carpathians, in Central Russia to the valleys of the Don and Dnieper (44 N. latitude). In North America, the ice fields extended up to 40 N latitude, where the cities of St. Louis and Philadelphia are now located. Although the Quaternary period as a whole was colder than previous geological eras, nevertheless, periods of glaciation in it alternated with interglacial periods, when the ice receded, and a temperate climate temporarily reigned on the earth. Over the past million years, there have been at least six ice and interglacial periods. Cooling led to the formation of distinct climatic zones, or zones (arctic, temperate and tropical), passing through all continents. The boundaries of individual zones were mobile and depended on the advancement to the south or retreat of glaciers, so the territory of the modern temperate zone has become the Arctic more than once for a while.

Four great glaciations are associated with the Quaternary. They were given the following names: Gunz, Mindel, Riss and Wurm. The duration of the glacial period, according to modern data, is about 200 thousand years, and the post-glacial period - 20 thousand years.

Modern man appeared in the era of glaciation. 25 thousand years ago, the last growth of ice sheets begins. They reached their maximum in the northern hemisphere 18 thousand years ago.

The culmination of glaciation did not last long, its general degradation began already 16 thousand years ago, and 5 thousand years later the volume of ice was halved. At this time, a slight cold snap set in, which halted the destruction of the ice sheets, but already 8 thousand years ago the Scandinavian ice sheet disappeared completely. In North America, the last traces of the once immense Laurentian ice sheet ceased to exist about 6 thousand years ago. The rapid degradation of ice sheets is explained not only by climatic conditions, but also by the very mechanism of ice movement, the peculiarities of the mechanics of a giant ice body located on the Earth's surface under conditions close to the melting point of this material.

The last interval during which we live is called the Holocene. This is a period of time from the beginning of the current interglacial, which began 10 thousand years ago and continues to this day. The interglacial is also not a frozen world, although it is not as rich in events as the ice age. In the Holocene, noticeable climatic fluctuations took place, which are well traced using both paleotemperature and other methods of reconstructing the past climate.

The early part of the Holocene was characterized by warming, which passed about 8 thousand years ago into the interval known as the "climatic optimum" and lasted for about 2.5 thousand years. During the optimum period, the average air temperature was higher than the present, and increased humidity was also noted, in particular in the Sahara and Rajasthan deserts in India.

The climatic optimum 5.5 thousand years ago was replaced by a cooling, then a new warming began, which culminated in a period of about 4 thousand years ago. The next cold snap coincided with the period of the wars for Troy and the travels of Odysseus.

It should be said that climatologists distinguish between geological, historical and modern climate changes. Earlier it was about geological changes, which are studied only by geological and geophysical methods. The historical ones include climate changes that occurred during the development of civilization before the beginning of instrumental observations. When studying them, in addition to geological and geophysical methods, archaeological and written monuments are used. Modern climate changes refer only to the period of instrumental observations.

Following the first historical cooling, culminating about 3 thousand years ago, a new warming began, which continued in the first millennium of our era, known as the "small climatic optimum". This period can also be called the period of forgotten geographical discoveries (Norman), in contrast to the period of the Great geographical discoveries of the 15th and 16th centuries.

The warming of the early Middle Ages led to a decrease in moisture in Europe, evidence of which is found in peat deposits in Central Europe. In Russia until the end of the 10th century. there were also favorable climatic conditions: crop failures rarely occurred, there were no very severe winters and severe droughts. Let us remember that it was at this auspicious time that the route "from the Varangians to the Greeks" was opened and intensively used.

In the first quarter of our millennium, a gradual cooling begins.

In Russia, the beginning of the second millennium AD was marked by a sharp deterioration in climatic conditions. A period of terrible thunderstorms, great droughts, and severe winters began.

In general, this cooling period, the closest to us, known as the Little Ice Age, lasted until the 19th century. and was replaced by new warming. Geological and geophysical traces of the Little Ice Age, as well as written sources, indicate that this was a global phenomenon - it manifested itself in the northern hemisphere from Western Europe to China, Japan and North America. In the southern hemisphere, traces of a cold snap are not so clear, but they also exist.

On the graph of changes in the average air temperature near the Earth's surface for the Holocene period, it can be seen that after the climatic optimum at the beginning of the Holocene, with all subsequent decreases and increases in temperature, there is a general trend towards cooling.

In the 20th century, an increase in the average annual temperature began at an intensive pace.

From 1901 to 2000, the average annual global surface air temperature increased by 0.6 ± 0.2 ° С, but this process was uneven over time. Experts distinguish three periods of abnormal temperature changes: warming in 1910-1945, a slight relative cooling in 1946-1975, and the most intense warming that began in 1976. The warmest decade was the 1990s, and the warmest year was 1998. True, it would not be superfluous to emphasize that warming occurs only in the troposphere, that is, within a few kilometers from the earth's surface, and in the upper atmosphere, the temperature decreases. / 3, p. 56 /

What happened to the climate in Russia in the second half of the 20th century? The general trend is the same as on the planet as a whole - an increase in the average annual air temperature. The most intense positive trend was noted in the Baikal region - Transbaikalia (3.5 ° С over 100 years). Biologists note that such changes have already affected the unique ecosystem of Lake Baikal: the total mass of plankton has increased, algae of more thermophilic species have appeared. It has also warmed up in the Amur region - Primorye and in Central Siberia. Large above zero temperature anomalies persisted in these regions over the past 11-12 years. The average temperature across the territory of Russia was maximum in 1995 (deviation from the norm - 1.9 ° C).

Climate change is a heterogeneous process. In Russia as a whole, warming is more noticeable in winter and spring (the trend was, respectively, 4.7 and 2.9 ° C over 100 years); in the warm season, the temperature rise is weaker. In addition, areas of warming alternate with areas of noticeable cooling.

Climate is the set of conditions that the ocean-land-atmosphere system goes through over time periods of several decades. At the same time, it is important to know how often each of the possible states occurs in this set - then you can find the average value over the entire set for any quantitative characteristic of these states.

The instantaneous state of the ocean-land-atmosphere system is called weather. It is characterized by a certain set of global fields, i.e., distributions over the globe of a number of characteristics of sea water, atmospheric air, the Earth's surface and the topsoil. For water and air, you need to take the temperature, pressure, concentrations of thermodynamically active impurities (for sea water - salt, for air - vaporous moisture, liquid water and ice in clouds and fogs, carbon dioxide, dust of various nature) and vector velocities. On the surface of the Earth, you need to know the flows of heat and TAN (first of all, evaporation and precipitation), the presence of snow and ice cover (and their thickness), for land, in addition, the nature of vegetation, soil moisture, moisture runoff.

The periods of time of several decades indicated in the definition of the climate are chosen so that the characteristics of the climate determined for these periods are the most stable, that is, they would change least of all during the transition from one such period to another. Indeed, actual data (for example, on air temperature) show that at shorter averaging periods (say, over a year or several years), the average values turn out to be more volatile (this is the so-called inter-annual, as well as shorter-period weather variability ). The significantly longer-term climate variability is also more intense, say, with periods of thousands of years.

The climate is formed under the influence of a number of factors, which can be divided into three groups.

1. External, or astronomical, factors - the luminosity of the Sun, the position and movement of the planet and the solar system, the inclination of its smallpox rotation to the orbital plane and the rotation speed, which determine the impact on the planet from other bodies of the solar system - its insolation (exposure to solar radiation) and the gravitational effects of external bodies that create tides and fluctuations in the characteristics of the planet's orbital motion and proper rotation (and therefore fluctuations in the distribution of insolation along the outer boundary of the atmosphere).

2. Geophysical and geographical factors - a number of planetary features, of which the most important for the Earth's climate are the properties of the lower boundary of the atmosphere - the underlying surface - and, above all, those properties that determine its dynamic and thermal interaction with the atmosphere and the exchange of thermodynamically active impurities with it. Of these properties, apparently, the first place should be named the geographical distribution of continents and oceans.

3. Atmospheric factors - the mass and composition of the atmosphere (including its main constituent parts, and specific TLP).

We do not yet know whether the climate is uniquely determined by all these factors, or if the same fixed values of all climate-forming factors can result in different climates. The second of these assumptions arises due to the fact that over the past 0.6-1 million years, no sharp changes in climate-forming factors seem to have occurred, but there were sharp fluctuations in climate - alternation of glacial and interglacial periods lasting tens of thousands of years. We will analyze them in detail below, but here we will consider the changes in climate-forming factors that occurred during the history of the Earth, and the evolution of the climate generated by them.

It seems easiest to attribute climate and even weather changes to changes in solar radiation. Indeed, the difference in air temperatures at the Earth's surface between day and night, equators and poles, summer and winter is created by the difference in the amount of incoming solar radiation: the greater this amount, the higher the temperature; So can it be assumed by analogy that during periods with a warm climate, the solar radiation coming to the Earth was increased, and during the ice ages it decreased (this hypothesis was proposed by the Irish astronomer E. Enik). However, such a simple reasoning may turn out to be incorrect if small increases in solar radiation will lead on the Earth to an increase in evaporation, an increase in cloudiness, an increase in winter snowfalls, snow melting due to increased cloudiness and, as a consequence, to an increase in glaciers and a decrease in temperature (G. Simpson) However, most experts on the evolution of stars, in contrast to E. Epiku, believe that the Sun and other stars of the same type ("yellow dwarfs" of spectral class G-2) have very stable radiation, which changes little over a time of about 10 billion years ( time of their stay on the so-called main sequence of stars on the luminosity-color diagram). Note that short-period fluctuations of the total luminosity of the Sun are not observed either - the energy flux coming from it, at an average distance of the Earth from the Sun of 1.952 cal per 1 cm2 per minute, apparently does not experience any currency changes in time (and therefore this the value is called the solar constant).

For the reasons stated above, only factors that are not associated with any changes in the luminosity of the Sun will be considered in the future. It seems that of these, the slowest climate changes could be caused by the geochemical evolution of the hydrosphere and atmosphere, as well as by the tidal evolution of the Earth-Moon system.

The mass of water vapor has a positive feedback with the greenhouse effect, since the saturating water vapor concentrate increases with increasing temperature: pair. There are no reliable calculations of changes in the course of the Earth's history of the masses of water vapor and carbon dioxide in the atmosphere so far, so that the possibility of corresponding changes in climate (primarily air temperature) is not yet excluded. However, paleontological data, convincingly demonstrating the continuity of the development of life, indicate that no climatic catastrophes have occurred on Earth.

Let us now turn to the possible climatic consequences of the tidal evolution of the Earth-Moon system. This system can be viewed as a complex top, consisting of two bodies rotating around their axes and around a common center of gravity (all these rotations have the same direction: if viewed from the North Star, then counterclockwise). To simplify the description of this system, we will neglect the influence on it from other celestial bodies. Then the total angular momentum of all the specified rotations will not change with time. It can be assumed with high accuracy that the vector sum of the angular momenta of the Earth's own rotation and the orbital motion of the Moon is constant.

If there was no friction in the Earth's body, then the tidal humps formed on the Earth's surface due to the attraction of the Moon would be directed exactly along the line connecting the centers of these bodies. But because of friction, they are carried away by the rotation of the Earth, much faster than the angular motion of the Moon in its orbit, so that their axis forms a certain lag angle b with the line of the Earth-Moon centers (and at each point on the Earth, the maximum tide occurs later than the moment of the maximum height of the Moon in the sky). The tidal hump closest to the Moon is attracted by it more strongly than the distant one, and this creates a moment of forces on Earth that tends to turn the planet opposite to its own rotation. The Earth's rotation must slow down so that its own angular momentum will decrease. Accordingly, the angular momentum of the moon will increase. But it follows from Kepler's third law that the angular momentum of a planet in its orbit is proportional to the square root of the mean radius of the orbit (or the cube root of the planet's orbital period). Consequently, we let the Moon move away from the Earth (and its angular motion in orbit will slow down).

Calculations have shown that due to tidal friction, the Earth's rotation slows down so that the length of the day increases by 0.0017 s per century. Because of this tiny increase over the millennia, there is already a very noticeable difference. So, the average length of a day over the past 2000 years was 0.017 s less than modern days, therefore, a difference of 3.5 hours has accumulated. This means that if we calculate the time of any solar eclipse that occurred 2000 years ago, using the current duration of the day, then we will be mistaken against the true time of the eclipse by 3.5 hours. During this time, the Earth rotates by 52, ° 5 in longitude - so big will be our error in determining the place of observation of this eclipse. This calculation shows that the evidence of the ancient historian alone about the observation of a solar eclipse in such and such a year at one point or another, say in Ancient Greece or in Babylon, may be sufficient for a fairly accurate assessment of the tidal slowdown of the Earth's rotation. The estimates obtained in this way turn out to be very close to the above figure of 0.0017 s per century.

J. Wells (1963) found another way to empirically estimate the tidal slowdown of the Earth's rotation - according to the microscopic annuals in the diurnal growth rings, which he discovered in the sections of some fossil corals, which makes it possible to count the number of days per year in the corresponding geological epoch. According to astronomical theories of the stability of planetary movements, the length of the year can be considered practically unchanged. Therefore, for example, obtained from corals of the Middle Devonian, whose age is about 380 million years, the figure of 400 days a year means that the length of the day at that epoch was 21.7 hours. These estimates are in very good agreement with those given above.

The inclination of the planet's equator to the plane of its orbit to the solar system is of extremely great importance for the climate. On Earth, in the past, the slope of e was less than the current one, so that seasonal changes in the weather turned out to be weaker, and the difference between the equator and the poles was greater (less solar heat got into the poles), latitudinal zoning was more pronounced, the general circulation of the atmosphere was more zonal and intense. These conditions were favorable for the development of glaciation in the polar regions, especially in the presence of continents in them, and this, apparently, can try to explain the traces of many Precambrian glaciations discovered by geologists.

After the geochemical evolution of the hydrosphere and atmosphere and the tidal evolution of the Earth, the movement of continents and poles appears to be the next fastest-changing factor in climate evolution. It occurs at speeds of the order of centimeters per year, so that changes in global scales, that is, displacements of thousands of kilometers, are formed over hundreds of millions of years. Without knowledge of the distribution of continents in a given geological epoch, it is impossible to correctly interpret the readings of paleoclastic indicators about the paleoclimates of specific regions.

Due to the fact that the daily amounts of solar heat coming to the upper boundary of the earth's atmosphere do not depend on longitude, the climate, despite the differences created by continents and oceans, has a pronounced latitudinal zonality. Earlier, when the masses of the ocean and atmosphere were less, the Earth rotated faster and the inclination of the equator to the ecliptic was less than the modern one, each of these factors made the latitudinal zoning of the climate even sharper than now. This zoning is as follows. In the equatorial zone, strong heating of the earth's surface creates intense convection with the formation of powerful cumulus clouds and heavy rainfall, so that this zone is wet. The upward movements are compensated here by the inflow of air to the equator in the lower layers of the atmosphere (trade winds) and their outflow in the higher layers. In the subtropics, the outflowing air is deflected by the rotation of the Earth to the east, and the cells of the trade wind circulation are forced to close in downward movements, so that the subtropical zones turn out to be arid (arid). Further to the poles, heat is transferred by mobile cyclops, which are formed in the west-eastern currents of striking latitudes and are accompanied by abundant precipitation, so that these zones again turn out to be humid. P. M. Strakhov used these properties of the sprat zoning of the climate in his Phanerozoic paleoclimatic reconstructions, which revealed the movement of the poles (according to those done on a fixist basis without taking into account the movement of Coptinepts).

In the absence of latitudinal zoning of the climate, there would be no seasonal fluctuations in the weather. Therefore, evidence of the presence of seasonal weather fluctuations in a particular geological epoch is evidence of the latitudinal zoning of the climate of that epoch. Such evidence is, first of all, rocks with annual layers, the so-called barbites, which are found in almost all geological periods of the Fansrozoic.

Many rocks can serve as qualitative indicators of climatic zones. So, in arid zones, evaporites are formed - dolomites, anhydrites, gypsum, potassium and rock salts, precipitated from solutions under conditions of strong evaporation, as well as carbonate red flowers (weathering products depleted in silica and colored with iron oxides) and loesses.

The most prominent climatic events in the history of the Earth were, of course, the ice ages, characterized by the emergence of continental ice sheets (currently such sheets cover Antarctica and Greenland). As already noted, geologists have discovered numerous tillites of both Phaperozoic and Precambrian ages. The most ancient of them are, apparently, the Lower Proterozoic.

In the Middle Proterozoic, Lower and Middle Riphean, on all continents there are numerous elephants of unsorted conglomerates, sometimes similar to pillites, but there is no clear picture here, as for the Lower Proterozoic. On the other hand, numerous tillites were found in the Upper Riphean and Vendian in different parts of the world (Fig. 59), which correlate well with each other and are grouped mainly by two ages - the lower ones about 750-800 Ma (Upper Riphean glaciation) and the upper ones about 650 —680 million years (Vendian glaciation).

The climate came to the next Ice Age (Carbopa and Permian), apparently, as a result of a gradual cooling, noticeable from the curve in Fig. 58 (during which the South Pole moved from West Africa through Brazil and Argentina to Antarctica, leaving on its way the aforementioned chain of Silurodebop tillites).

The first large region, which was affected by the Kaipozoic cooling of the climate, was, naturally, Antarctica. Now the ice sheet on it, according to the summary of V.I.Bardin and I.A.Suetova (1967), has an area of about 14 million km2 and a volume of 24 million km the shield is 2.6 million km3; less than 1% remains on the Arctic and mountain glaciers); melting all Antarctic ice would raise the level of the World Ocean by 55 m.About 83% of Antarctic ice is concentrated in the ice dome of East Antarctica up to 3.6 km thick, the bottom of which lies mainly above sea level, and the surface is on average above 2 km above sea level ... Separated from it by the Transantarctic Mountains, the West Antarctica ice sheet lies mainly on the ocean floor and on a number of islands includes huge floating ice sheets in the Ross and Weddell Seas. Atmospheric precipitation over Antarctica, on average only about 150 mm per year, according to some estimates, is now slightly higher than the loss of ice (mainly by the separation of icebergs).

Geological sections on the King George and Seymour Islands and in South Australia (separated from Antarctica only at the end of the Eocene), as well as materials from the bottom sediment columns of the Southern Ocean, indicate that the Antarctic ice sheet was formed only in the Miocene - about 20 million years ago - and since then it has existed to our time (this is also confirmed by data on the drop in the level of the World Ocean by many tens of meters.

Climate, by definition, is a global concept, and certain manifestations of each ice age are naturally found in all regions of the world, but, of course, they are by no means everywhere and not always reduced to the growth of glaciers. In total, 14% of the Earth's surface was covered with ice, twice as much as it is now. Ice sheets reached 48 ° 30 "in Europe and 37 ° latitude in North America.

The maximum volume of land ice in the Pleistocene was 56.1 million km, including 23.9 in Antarctica (as it is today), 23.9 in North America, 7.6 in Europe and 0.7 in the Urals. Siberian region (60% of this ice was concentrated in the northern and 40% in the southern hemisphere, whereas now these figures are equal to 8 and 92%).

Ministry of Education and Science of the Russian Federation

Federal State Budgetary Educational Institution

higher professional education

"STATE UNIVERSITY OF MANAGEMENT"

Institute of Financial Management and Tax Administration

Department of Innovation Management in the Real Sector of the Economy

In the discipline "ENOIT"

On the topic: Climate of the Earth in the past, present, future. Its influence on the development of civilization

Work completed:

Razgulyaeva Arina Nikolaevna

Management 1-1, 1 course

Moscow, 2014

INTRODUCTION

DOCEMBRIA CLIMATE

PALEOZOIC CLIMATE

MESOZOIC CLIMATE

CLIMATE OPTIMUM

MEDIEVAL CLIMATE

SMALL ICE PERIOD

THE CLIMATE OF THE NEAR FUTURE

IMPACT OF CLIMATE ON THE DEVELOPMENT OF CIVILIZATION

CONCLUSION

LIST OF PRIMARY SOURCES

INTRODUCTION

Relevance

In the last decade, the problem of studying ancient climates has acquired particular importance in connection with the possibility of their use to refine the forecasting of the climate of the near and distant future. The particular importance of the problem of the future climate of the planet is determined by the fact that human economic activity depends entirely on climatic conditions. But in recent years, as a result of the economic activities of people, major climate changes are possible. Unintentional global environmental pollution by fuel combustion products occurring on a regional and global scale, land reclamation and irrigation works, construction of hydroelectric power plants and reservoirs, destruction of forests on huge areas, etc. can cause climatic changes similar in nature and size to global natural climate changes that have occurred in the geological past.

purpose of work

Show:

.Changes in the Earth's climate during its development

.The relationship between the climate of the past, present and future

.The influence of climate on the development of civilization

1. Precambrian climate

When did the Earth's climate arise? The term "climate" was coined by the ancient Greek astronomer Hipprachus of Nicea in the 2nd century BC. According to modern concepts, the climate arose after the bowels of the Earth began to warm up, and deep "rivers" carrying heat began to form in them. At this time, various gas compounds began to flow through the molten sections of the earth's crust to its surface. This is how the first atmosphere was formed. It consisted of a mixture of carbon dioxide, ammonia, nitrogen, water vapor, hydrogen, sulfur compounds and vapors of strong acids. The absolute predominance of carbon dioxide in it and the high content of water vapor contributed to the fact that such an atmosphere easily let in sunlight. As a result, this led to a strong increase in temperatures, which could reach about 500 ° C. For example, similar temperatures are typical for the surface of Venus.

Later, as a result of a gradual decrease in the amount of carbon dioxide, ammonia and water vapor in the atmosphere and the appearance of other gases, the so-called greenhouse effect began to subside. Temperatures on Earth began to drop. This, in turn, facilitated the condensation of water vapor. The hydrosphere arose. With its formation, a new stage in the development of organic substances began. Water is the first environment in which life was born and developed.

The first microscopic organisms appeared more than 3.8 billion years ago. This time was rather uncomfortable for living beings. A dense atmosphere without oxygen, the planet's surface constantly splitting by the strongest earthquakes, huge flows of deep molten matter and gases constantly escaping from the depths. There were no conditions in the water for the development of organisms at that time. The water was constantly boiling. Few microscopic organisms could exist in such an environment.

Over time, the inner activity of the planet subsided. Less and less ammonia and carbon dioxide were released from the depths, what entered the atmosphere was used for oxidation processes and was used by microscopic organisms for the formation of siliceous and carbonate rocks. Perhaps in connection with this, the temperature began to decrease on Earth. On a geological scale, it happened very rapidly, and already 2.5-2.6 billion years ago, it got so cold that the first glaciation began on the earth's surface.

Studying the strata of rocks that arose in that period, geologists more than once noticed the presence in them of formations similar to modern moraines. These were well-polished boulders and clusters of very hard pebbles with numerous streaks and scars that could only have been left by the sharp edges of the rocks soldered into the ice. All this testified to the glacial nature of the relief and rocks, but at the same time contradicted the existing opinion about the dominance of high temperatures and a very warm climate at that distant time. A careful study of the traces of glaciation in the Precambrian era led to the fact that irrefutable evidence was found for the existence of extensive glacial ice sheets in ancient times.

In the Precambrian, according to the development of ancient moraine deposits and related formations, the existence of the following glaciation epochs is distinguished. The most ancient glaciation occurred 2500-2600 million years ago, and is called Huron. Moraines of these years are known in Europe, South Asia, North America, and Western Australia.

Traces of glaciation with an age of about 950 million years have been found in Greenland, Norway and on the island of Svalbard. About 750 million years ago, the Sturtian glaciation occurred in Australia, China, in the ego-west of Africa and in Scandinavia. The Varangian glaciation is most pronounced, which occurred 660-680 million years ago. These glacial rocks are found in North America, Greenland, Svalbard, the British Isles, Scandinavia, France, China, Australia, Africa, South America and northeastern Russia.

Low temperatures persisted for a fairly long period. Then the temperatures on the earth's surface increased, the ice melted, the level of the World Ocean rose, and again a favorable time came for the flourishing of microscopic organisms and blue-green algae.

2. Climate of the Paleozoic

The Paleozoic began with a colossal flood of seas that followed the emergence of vast parts of the land in the Late Proterozoic. Most geologists believe that at that time there was a single huge continental block called Pangea (translated from Greek - "the whole earth"), which was surrounded on all sides by the world's oceans. Later, this single continent fell apart.

Cambrian period (570-490 million years ago)

There is very scanty and fragmentary information about the climate of the Cambrian period. After the development of ice sheets on many continents (South America, Africa, Australia, Northern Europe), significant warming occurred at the beginning of the Cambrian. Tropical conditions were created practically on all continents. This is evidenced by the presence of a rich thermophilic complex of marine fauna. The tropical coasts of the continents were bordered by giant stromatolite reefs, much like the coral reefs of modern tropical waters. It is assumed that for the seas of Siberia in the Early Cambrian, the water temperature did not fall below 25 ° C.

Ordovician period (490-440 million years ago)

During the Ordovician period, the climate underwent significant changes. Throughout the period, land masses shifted farther and farther south. The old Cambrian ice sheets have melted and sea levels have risen. Most of the land was concentrated in warm latitudes. An analysis of the climatic conditions of this period suggests that in the Middle and Late Ordovician there was a significant cooling that covered many continents.

Silurian period (440-400 million years ago)

At the very beginning of the Silurian period, relatively cool conditions continued to prevail on the continents. For this time, small thickness glacial formations are known in Bolivia, in the north of Argentina and in the east of Brazil. It is possible that glaciers could cover some areas of the Sahara. Gondwana has moved towards the South Pole. The land masses that form North America and Greenland were converging. They eventually collided to form the giant supercontinent Laurasia. It was a period of intense volcanic activity and intense mountain building. Cooling at the beginning of the early Silurian was relatively quickly replaced by warming, which was accompanied by a gradual migration to the poles of the subtropical climate. Whereas in the northeast of Brazil, at the beginning of the Early Silurian, there are strata of moraines, then later these sediments begin to be dominated by weathering products characteristic of a warm climate. Warming has led to the emergence of a climate close to subtropical in high and middle latitudes.

Devonian period (400-350 million years)

Scientists believe that since thermophilic species of organisms and sedimentary formations were widely represented on the continents in the Devonian period, temperature fluctuations were unlikely to go beyond the tropical climate. The Devonian period was the time of the greatest cataclysms on our planet. Europe, North America and Greenland collided with each other, forming the huge northern supercontinent Laurasia. At the same time, huge masses of sedimentary rocks were pushed up from the ocean floor, forming huge mountain systems in the east of North America and in the west of Europe. The erosion of the rising mountain ranges has resulted in the formation of large amounts of pebbles and sand. They formed extensive deposits of red sandstone. The rivers carried mountains of precipitation into the seas. Vast swampy deltas were formed, which created ideal conditions for animals who dared to take the first, such important steps from water to land. By the end of the period, the sea level had dropped. The climate has warmed over time and became harsher, with alternating periods of heavy rains and severe droughts. Large areas of the continents have become waterless.

Carboniferous period (350-285 million years)

In the early Carboniferous, the planet was dominated by a humid tropical climate. This is evidenced by the wide distribution of carbonate deposits, a thermophilic type of marine fauna. Humid tropical conditions are typical for a large part of the continents in both the northern and southern hemispheres. In the Middle and especially Late Carboniferous, climatic zoning is clearly manifested. One of the characteristic features of this time is a significant cooling and the appearance of large ice sheets in the southern hemisphere, which in turn led to a sharp reduction in the subtropical and tropical zones and a general decrease in temperature. Even in the equatorial belt, average temperatures in the Late Carboniferous decreased by 3-5 ° C. Also, along with the cooling in a number of areas, signs of a drying out of the climate appeared.

Permian period (285-230 million years)

The climate of the Permian period was characterized by pronounced zoning and increasing aridity. In general, we can say that it was close to the modern one. For the early Permian, with the exception of the western hemisphere, there are tropical, subtropical and temperate belts with different moisture regimes. At the beginning of the period, glaciation continued, which began in the Carboniferous. It was developed on the southern continents. Gradually the climate becomes very dry. Perm is characterized by the most extensive deserts in the history of the planet: sands even covered the territory of Siberia.

3. Climate of the Mesozoic

Triassic period (230-190 million years)

In the Triassic period, the earth was dominated by a flat relief, which predetermined the wide distribution of the same type of climates over vast areas. The climate of the Late Triassic was characterized by high temperatures and a sharply increased degree of evaporation. For the Early and Middle Triassic, it is difficult to draw thermal zoning, since only high temperatures are almost ubiquitous. Relatively cool conditions existed in the extreme northeast of Eurasia and in the northwest of the North American continent. Landscapes remained desertified, and vegetation grew only on flooded lowlands. Shallow seas and lakes evaporated intensively, which is why the water in them became very salty.

Jurassic period (190-135 million years)

During the Early and Middle Jurassic, not only thermal zoning existed, but also zoning caused by differences in humidity. In the Middle Jurassic there were tropical, subtropical and temperate belts with different moisture regimes. Within the tropical and equatorial zones, intense chemical weathering took place, thermophilic vegetation grew, and tropical fauna lived in shallow seas. In the late Jurassic, tropical, subtropical and temperate zones are distinguished by the nature of the temperature regime. The temperature for the late Jurassic epoch ranged from 19-31.5 ° C. For the Late Jurassic epoch, there are no reliable indicators to identify the equatorial belt. Probably, equatorial conditions with seasonal moisture existed mainly in Brazil and Peru. On the African continent and in southern Eurasia in the equatorial part, desert landscapes probably predominated.

Cretaceous period (135-65 million years)

During the Cretaceous Era, there were equatorial, vast tropical, subtropical and temperate zones on Earth. 70 million years ago, the Earth cooled. Ice caps have formed at the poles. The winters were getting harsher. The temperature dropped in places below +4 degrees. For the dinosaurs of the Cretaceous period, this change was sharp and very noticeable. Such temperature fluctuations were caused by the split of Pangea, and then Gondwana and Laurasia. The sea level rose and fell. The jet streams in the atmosphere have changed, as a result of which the currents in the ocean have changed. At the end of the Cretaceous, temperatures began to rise sharply. There is a hypothesis that the oceans were the cause of these changes: instead of absorbing heat, they may have reflected it back into the atmosphere. Thus, they caused the greenhouse effect.

4. Climatic optimum

Warming began about 15 thousand years ago. The ice sheet began to shrink and recede. After him, plants moved, which gradually mastered more and more new areas. During the climatic optimum, the area of polar sea ice in the Arctic Ocean has decreased significantly. The average water temperature in the Arctic was several degrees higher than at present. The presence of relatively high temperatures at that time is evidenced by the significant expansion of the habitat of some animals. The warm climate in Europe has encouraged the movement of many plant species northward. During the climatic optimum, the border of the snow line has greatly increased. In the mountains, forests have risen almost 400-500 m above the current level. If the temperature during the period of climatic optimum in the middle latitudes increased everywhere, the humidity changed very unevenly. It increased in the north of the European part of Russia, while south of the 50s, it, on the contrary, decreased. In this regard, the landscapes of steppes, semi-deserts and deserts were located north of the modern ones. In Central Asia, the Near and Middle East, humidity during the climatic optimum was much higher than at present. A warm and humid climate only 10 thousand years ago existed in all now arid regions of Asia and Africa.

It is worth paying attention to the history of the Sahara Desert. Approximately 10-12 thousand years ago, in the south of the present-day Sahara, there were two huge freshwater lakes with dense tropical vegetation on the shores, which were not inferior in size to the modern Caspian Sea. However, the favorable period of climatic optimum quickly came to an end. Drought began to appear more and more often, and finally, under the pressure of the sands, the vegetation disappeared, the rivers and lakes dried up.

Warming traces are well preserved even in Antarctica. In particular, these are traces of water erosion, showing that at times the ice in Antarctica thawed, and streams of water washed away the thawed soil.

During the climatic optimum, it was not only warm, but also humid, especially in those areas that are now considered arid. General warming has led to a shift towards the poles of climatic zones, and the atmospheric circulation has changed. The now arid areas received a lot of rainfall. If you carefully study the surface of modern deserts on a map, you can clearly see dry channels along which rivers previously flowed, and saucer-shaped lowlands that were lakes in the past.

The climate had a direct impact on the economic activities of people. With the beginning of the climatic optimum, one of the most favorable stages in the life of mankind begins. This period was characterized not only by a high level of making tools from stone, but also by the transition to a sedentary lifestyle. The emergence of agriculture and animal husbandry was associated not only with changes in climatic conditions, but also with unreasonable economic activities. The favorable climate has contributed to the widespread distribution of forests and wild animals. People were looking for, mined and consumed for food that was not difficult to get, that provided by nature. But nothing was created in return. Over time, the number of animals, especially large ones, began to decline. It was easier for people to kill a large animal together than to hunt down several small ones for a long time. In addition, the hunters killed the strongest and fittest animals, and the sick and old fell to the predators. Thus, primitive people undermined the basis of animal reproduction.

Unsuccessful hunting, long journeys in search of animals, the number of which was greatly reduced, prompted the ancient people to begin to domesticate animals. The most ancient regions of domestication were the territories of the present-day Sahara Desert, between the Tigris and Euphrates, Indus and Ganges. At first, the tribes of pastoralists wandered in order to find suitable pastures. The number of livestock increased, and it became more difficult to find open areas. Pastoralists, like farmers, began to burn forests and use free land for pastures and arable lands. Land development in zones subject to climatic changes led to the disruption of the established balance for centuries. The moisture circulation and temperature regime of the Earth changed. Mass grazing of livestock contributed to the rapid degradation of the soil cover. The destroyed forests, savannas and pastures were not restored. With the onset of drought in connection with the onset of cooling in the areas of the once lush forests and savannas, semi-desert and desert landscapes arose.

From the preserved erosion marks in the river valleys, it has been established that the high flow of the Nile, Tigris, Euphrates, Indus, Ganges and other rivers in the past has changed quite strongly. After the climatic optimum, the level of the World Ocean dropped by almost 3 m. In conditions of aridity, people needed to develop irrigated agriculture. Preserved complex irrigation structures, created by the hands of ancient people. The development of irrigated agriculture did not help, but only postponed the complete depletion of the soil. Many ancient settlements ceased to exist under the pressure of the advancing sands.

This period can be called the first environmental crisis. In the future, unreasonable management and human intervention in many natural processes more than once led to very undesirable results, some ended in disasters.

5. The climate of the Middle Ages

The climatic optimum ended in the II millennium BC. NS. A cold snap set in, which lasted until the 4th century. n. NS. After that, the Earth became warmer again. The warm period lasted from the 4th to the 13th century, that is, it covered the early Middle Ages.

In Europe, Mediterranean vegetation was no longer able to overcome the Alps. But nevertheless, the boundaries of the growth of thermophilic vegetation have moved almost a hundred kilometers to the north. Grain is being grown in Iceland again. The grapes were grown all over the southern coast of the Baltic Sea and even in England. The peak of warming in Iceland occurred in the 11th-12th centuries. It was warm everywhere: in America and in Asia. The ancient chronicles of China report that in the 7th-10th centuries. mandarins grew in the Yellow River Valley, which means that the climate of these territories was subtropical, and not temperate, as at present. During the period of low climatic optimum, a humid climate prevailed in Kampuchea, India, the countries of the Near and Middle East, Egypt, Mauritania and countries located in the south of the Sahara Desert.

The development of human society, various events in the life of peoples and states, interstate relations are well documented in Europe. Many peoples inhabited this continent in the early Middle Ages, but as an example, let us dwell on the life of the Vikings, since their sagas tell a lot about the natural conditions of the end of the 1st and the beginning of the 2nd millennia. Natives of Scandinavia, Vikings, in Russia they were called Varangians, made long transitions, seized foreign countries and mastered new lands. The conquests and transitions of the Vikings were facilitated by a warming climate. In the X century. Vikings discovered Greenland. This island owes its name to the fact that at that time it appeared to the Vikings in the form of an endless green carpet. On 25 ships, 700 people with belongings and cattle sailed across the North Atlantic and founded several large settlements in Greenland. The settlers in Greenland were engaged in cattle breeding and probably cultivated crops. It is hard to imagine that Greenland, this silent and thick island of ice, could have been in bloom just a thousand years ago. However, in reality this was the case. The Vikings did not stay in Greenland for long. Under the onslaught of the advancing ice and the developing cold snap, they were forced to leave this huge island. The ice well preserved the houses, outbuildings and utensils of the Vikings, as well as traces of livestock and even the remains of grain.

On small wooden ships, which had excellent seaworthiness, the Vikings sailed not only in the western direction and sailed to the coast of Canada, but also sailed far to the north. They discovered Svalbard, repeatedly entered the White Sea and reached the mouth of the Northern Dvina. All this gives reason to believe that at the beginning of the 2nd millennium in the Arctic, most likely, long-term thick ice was absent. In Svalbard, the remains of a fossil tundra soil, only 1,100 years old, have recently been discovered. Consequently, in the X-XI centuries. and even earlier on Svalbard not only was there no ice sheet, but also tundra and forest-tundra landscapes were located.

The reasons for the low climatic optimum of the Middle Ages:

1.Increased solar activity

.Rare volcanic eruptions

.Periodic fluctuations of the Gulf Stream associated with changes in the salinity of ocean water, which in turn depends on changes in the volumes of glaciers

6. Little Ice Age

After a warm epoch, a new cooling occurred, which was called the Little Ice Age. This period lasted from the XIV to the end of the XIX century. The Little Ice Age is divided into three phases.

First phase (XIV-XV centuries)

Researchers believe that the onset of the Little Ice Age was associated with a slowdown in the current of the Gulf Stream around 1300. In the 1310s, Western Europe experienced a real ecological catastrophe. The traditionally warm summer of 1311 was followed by four gloomy and rainy summers of 1312-1315. Heavy rains and unusually harsh winters killed several crops and froze fruit orchards in England, Scotland, northern France and Germany. Winter frosts began to affect even northern Italy. A direct consequence of the first phase of the Little Ice Age was the mass famine of the first half of the 14th century.

From around the 1370s, temperatures in Western Europe began to rise slowly, and mass famine and crop failures ceased. However, cold, rainy summers were frequent throughout the 15th century. In winter, snowfalls and frosts were often observed in southern Europe. Relative warming began only in the 1440s, and it immediately led to a rise in agriculture. However, the temperatures of the previous climatic optimum were not restored. Snowy winters are common in Western and Central Europe.

The influence of the Little Ice Age on North America was also significant. On the east coast of America it was extremely cold, while the central and western regions of the territory of the modern United States became so dry that the Midwest became a region of dust storms; mountain forests are completely burned out.

Glaciers began to advance in Greenland, the summer thawing of soils became more and more short-lived, and by the end of the century, permafrost was firmly established here. The amount of ice in the northern seas increased, and attempts to reach Greenland in the following centuries usually ended in failure.

Second phase (XVI century)

The second phase was marked by a temporary rise in temperature. Perhaps this was due to some acceleration of the current of the Gulf Stream. Another explanation for the "interglacial" phase of the 16th century is maximum solar activity. In Europe, an increase in average annual temperatures was again recorded, although the level of the previous climatic optimum was not reached. Some chronicles even mention the facts of "snowless winters" of the middle of the 16th century. However, from about 1560, the temperature began to drop slowly. Apparently, this was due to the beginning of a decrease in solar activity. On February 19, 1600, the volcano Huaynaputin erupted, the strongest in the history of South America. It is believed that this eruption was the cause of great climatic changes in the early 17th century.

Third phase (conditionally XVII - early XIX century)

The third phase was the coldest period of the Little Ice Age. The decreased activity of the Gulf Stream coincided in time with the lowest after the 5th century. BC NS. the level of solar activity. After the relatively warm 16th century, the average annual temperature in Europe dropped sharply. The global temperature dropped by 1-2 degrees Celsius. In the south of Europe, severe and long winters were often repeated, in 1621-1669 the Bosphorus froze, and in the winter of 1708-1709 the Adriatic Sea froze near the coast. All over Europe there was a spike in mortality.

Europe experienced a new wave of cooling in the 1740s. During this decade, the leading capitals of Europe - Paris, Petersburg, Vienna, Berlin and London - experienced regular blizzards and snow drifts. In France, snowstorms have been repeatedly observed. In Sweden and Germany, according to contemporaries, heavy snowstorms often swept the roads. Abnormal frosts were noted in Paris in 1784. Until the end of April, the city was under stable snow and ice cover. The temperature ranged from -7 to -10 ° C.

Causes of the Little Ice Age:

1.Increased activity of volcanoes, the ash of which eclipsed sunlight

.Decrease in solar activity

.Slowing down the Gulf Stream

7. The climate of the near future

What will the climate be like? Some believe that the planet will be colder. The end of the 19th and 20th centuries is a respite similar to that of the Middle Ages. After warming, the temperature will drop again and a new ice age will begin. Others say temperatures will rise steadily.

As a result of human economic activity, carbon dioxide enters the atmosphere in an increasing amount, creating a greenhouse effect; Nitrogen oxides enter into chemical reactions with ozone, destroying the barrier, thanks to which not only humanity exists on Earth, but all living things. It is well known that the ozone shield prevents the penetration of ultraviolet radiation, which has a detrimental effect on living organisms. Thermal radiation has already increased in large cities and industrial centers. This process will intensify in the near future. Thermal emissions, currently affecting the weather, will have a greater impact on the climate in the future.

It has been established that the amount of carbon dioxide is progressively decreasing in the earth's atmosphere. Throughout geological history, the content of this gas in the atmosphere has varied quite dramatically. There was a time when there was 15-20 times more carbon dioxide in the atmosphere than it is now. The temperature of the Earth during this period was quite high. But as soon as the amount of carbon dioxide in the atmosphere dropped, the temperatures dropped.

The progressive decrease in carbon dioxide in the atmosphere began about 30 million years ago and continues today. Calculations show that a decrease in atmospheric carbon dioxide will continue in the future. As a result of a decrease in the amount of carbon dioxide, a new severe cooling will occur, and glaciation will occur. This could happen in a few hundred thousand years.

This is a rather pessimistic picture of the future of our Earth. But it does not take into account the impact of human economic activity on the climate. And it is so great that it is equivalent to some natural phenomena. In the coming decades, the main impact on the climate will be exerted by at least three factors: the rate of growth in the production of various types of energy, mainly heat; an increase in the content of carbon dioxide in the atmosphere as a result of vigorous economic activities of people; change in the concentration of atmospheric aerosol.

In our century, the natural decrease in atmospheric carbon dioxide was not only suspended as a result of the economic activities of mankind, but in the 50s and 60s the concentration of carbon dioxide in the atmosphere began to slowly increase. This was due to the development of industry, a sharp increase in the amount of burned fuel required to generate heat and energy.

Deforestation, which continues in ever-increasing proportions, both in tropical countries and in the temperate zone, has a significant impact on the atmospheric carbon dioxide content and climate formation. A decrease in the area of forest tracts leads to two very undesirable consequences for mankind. First, the process of processing carbon dioxide and the release of free oxygen by plants into the atmosphere is reduced. Secondly, during deforestation, as a rule, the earth's surface is exposed, and this leads to the fact that solar radiation is reflected more strongly and instead of heating and storing heat in the surface part, the surface, on the contrary, cools.

However, when predicting the future climate, one must proceed from the actual trends caused by human economic activity. The analysis of numerous materials on anthropogenic factors affecting the climate allowed the Soviet scientist M.I. Budyko, back in the early 70s, give a fairly realistic forecast, according to which the increasing concentration of atmospheric carbon dioxide will lead to an increase in the average temperatures of the surface air by the beginning of the 21st century. This forecast at that time was practically the only one, since many climatologists believed that the cooling process, which began in the 40s of this century, would continue. Time has confirmed the correctness of the forecast. Even 25 years ago, the content of carbon dioxide in the atmosphere was 0.029%, but over the years it has increased by 0.004%. This, in turn, has led to an increase in global average temperatures of almost 0.5 ° C.

How will the temperatures on the globe be distributed after the rise? The greatest changes in the surface air temperature will occur in the modern arctic and subarctic zones in the winter and autumn seasons. In the Arctic, the average air temperature in the winter season will increase by almost 2.5-3 ° C. Such warming in the development of Arctic sea ice will lead to their gradual degradation. Melting will begin in the peripheral parts of the ice sheet and will slowly shift to the central regions. Gradually, the thickness of the ice and the area of the ice cover will decrease.

In connection with the change in the temperature regime in the coming decades, the nature of the water regime of the earth's surface should also change. Global warming on the planet by only 1 ° will lead to a decrease in precipitation in a significant part of the steppe and forest-steppe zones of the temperate climatic zone by about 10-15% and to an increase by about the same amount of the humidified zone in the subtropical zone. The reasons for this global change lie in a significant change in atmospheric circulation, which occurs as a result of a decrease in the temperature difference between the poles and the equator, between the ocean and the continents. During the warming period, the melting of ice in the mountains and especially in the polar regions will cause an increase in the level of the World Ocean. The increased area of the water surface will have a strong effect on the formation of atmospheric fronts, cloudiness, moisture content and will significantly affect the growth of evaporation from the surface of the seas and oceans.

It is assumed that in the first quarter of the XXI century. in the tundra zone, which by that time will completely disappear and will be replaced by the taiga zone, precipitation will mainly fall in the form of rains and the total amount of precipitation will far exceed the present day. It will reach 500-600 mm per year. Taking into account that the average summer temperatures in the modern tundra zone will rise to 15-20 ° С, and the average winter temperatures - up to minus 5-8 ° С, these areas will move to the temperate zone. Landscapes of coniferous forests (taiga region) will appear here, but the possibility of the appearance of a zone of mixed forests is not excluded.

With the development of warming in the Northern Hemisphere, the expansion of geographical or landscape-climatic regions will occur in a northern direction. Areas of uniform and variable moisture will expand strongly. As for areas with insufficient moisture, the change in temperature will affect the migration of areas of deserts and semi-deserts. Increasing moisture in tropical and equatorial areas will gradually reduce desert and semi-desert landscapes. They will shrink at the southern borders. However, instead of this, they will expand to the north. The arid areas will, as it were, migrate northward. It is also expected to expand within the temperate zone of the forest-steppe and steppe regions due to the reduction of the zone of deciduous forests.

8. Influence of climate on the development of civilization

Precambrian glacial climate

Human economic activity largely depends on the climate and is determined by it. At the dawn of the development of human society, the climate was one of the main factors that determined the choice of habitats and hunting places, places of collection, and later the cultivation of certain food products, etc. The climate even influenced the development of civilization. So, during the warming period, Icelandic settlers sent their colonists to the west of Greenland. As a result of the cold snap, the colony in Greenland fell into decay, and later the increase in cold led to the destruction of the main Norman colonies in Iceland.

The consistent intensification of drought in the Near and Middle East, which took place in the 1st millennium BC, led to the destruction of many of the largest cities and settlements for that time. Many of them later turned out to be buried under a layer of sand of the advancing deserts. Consequently, climate change in one direction or another led to very serious consequences for the development of civilizations.

Historical data provide a huge amount of material indicating that a cold snap or drought in ancient times led to a sharp reduction in agricultural production and, in connection with this, periodically hunger years began.

According to numerous estimates of climatologists, a changing climate may have an impact on food production, both regionally and globally. So, for example, after the Second World War, the yield of grain crops increased due to the introduction of new technology in soil cultivation, cultivation, the correct application of the required amount of fertilizers, the development of new drought-resistant and frost-resistant varieties, etc. In the last decade, world food production has grown by 3% per year, mainly due to the introduction of new agricultural land. But at the same time, the increase in food production, which took place during the 60s of the 20th century, sharply decreased in the early 70s and mainly in 1972 as a result of the unfavorable influence of climatic anomalies.

The climate has a great influence on the distribution of water and energy resources. There is no doubt that climate fluctuations are also expressed in changes in the circulation of the atmosphere, the total amount of atmospheric precipitation, the regime of precipitation and the total amount of river runoff. Despite the fact that water supply systems and reservoirs are designed with certain reserves, taking into account weather changes due to possible changes in the precipitation regime in the future, in regions located in an arid climate, there may be big problems with water supply to settlements and industrial facilities.

To a certain extent, climate changes, both in the direction of cooling and warming in the future, will make their own adjustments in the generation and consumption of energy. The non-renewability of fuel resources and their steady reduction over time create additional problems, which are especially pronounced when cold snaps occur.

Despite such an obvious dependence of human economic activity on climate, technical means, the level of development of science and especially the growth of technical capabilities in the foreseeable future can greatly change the nature of the impact of climate change.

Conclusion

Considering the process of the formation and development of the Earth's climate from the historical point of view, one can come to the conclusion that over the past 600 million years the climate has repeatedly changed with a certain frequency. In accordance with climatic fluctuations, natural conditions changed, the composition of the atmosphere changed, organic life developed, and the habitats of plants and animals expanded. Over time, new types of climate and previously unknown landscape and climatic conditions arose.

Numerous studies of climatologists from different countries indicate that human economic activities associated with the burning of fossil fuels in an ever-increasing quantity, as well as the reduction of forests, will ultimately lead to a change in the chemical composition of the atmosphere. It can be expected that in the coming decades the concentration of carbon dioxide in the atmosphere will increase to one and a half times, and in the first quarter of the 21st century - almost 2 times compared to the modern era. For reliable forecasting, and, most importantly, for determining the general direction of human economic activity in the coming decades, it is necessary to correctly imagine not only the nature or trend of temperature changes, but also to give an objective description of the expected changes in natural conditions. This invaluable help is provided by determining the time of existence of similar climatic conditions in the geological past and comparing natural conditions with those expected in the future.

List of primary sources

1. Yasamanov N.A. Entertaining climatology. 1989.

Yasamanov N.A. Ancient climates of the Earth. 1985

Wikipedia is the free encyclopedia. http://ru.wikipedia.org/wiki/Little_glacial_period

Http://www.fio.vrn.ru/2004/7/index.htm

BBC "Climate Wars" (documentary) 2008

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Ministry of Education and Science of the Russian Federation

Federal State Budgetary Educational Institution

higher professional education

"STATE UNIVERSITY OF MANAGEMENT"

Institute of Financial Management and Tax Administration

Department of Innovation Management in the Real Sector of the Economy

In the discipline "ENOIT"

On the topic: Climate of the Earth in the past, present, future. Its influence on the development of civilization

Work completed:

Razgulyaeva Arina Nikolaevna

Management 1-1, 1 course

Moscow, 2014

INTRODUCTION

DOCEMBRIA CLIMATE

PALEOZOIC CLIMATE

MESOZOIC CLIMATE

CLIMATE OPTIMUM

MEDIEVAL CLIMATE

SMALL ICE PERIOD

THE CLIMATE OF THE NEAR FUTURE

IMPACT OF CLIMATE ON THE DEVELOPMENT OF CIVILIZATION

CONCLUSION

LIST OF PRIMARY SOURCES

INTRODUCTION

Relevance

purpose of work

Show:

.Changes in the Earth's climate during its development

.The relationship between the climate of the past, present and future

.The influence of climate on the development of civilization

1. Precambrian climate

2. Climate of the Paleozoic

Cambrian period (570-490 million years ago)

Ordovician period (490-440 million years ago)

Silurian period (440-400 million years ago)

Devonian period (400-350 million years)

Carboniferous period (350-285 million years)

Permian period (285-230 million years)

3. Climate of the Mesozoic

Triassic period (230-190 million years)

Jurassic period (190-135 million years)

Cretaceous period (135-65 million years)

4. Climatic optimum

5. The climate of the Middle Ages

The reasons for the low climatic optimum of the Middle Ages:

1.Increased solar activity

.Rare volcanic eruptions

.Periodic fluctuations of the Gulf Stream associated with changes in the salinity of ocean water, which in turn depends on changes in the volumes of glaciers

6. Little Ice Age

After a warm epoch, a new cooling occurred, which was called the Little Ice Age. This period lasted from the XIV to the end of the XIX century. The Little Ice Age is divided into three phases.

First phase (XIV-XV centuries)

Second phase (XVI century)

Third phase (conditionally XVII - early XIX century)

Causes of the Little Ice Age:

1.Increased activity of volcanoes, the ash of which eclipsed sunlight

.Decrease in solar activity

.Slowing down the Gulf Stream

7. The climate of the near future

8. Influence of climate on the development of civilization

Precambrian glacial climate

Conclusion

List of primary sources

1. Yasamanov N.A. Entertaining climatology. 1989.

Yasamanov N.A. Ancient climates of the Earth. 1985

Wikipedia is the free encyclopedia. http://ru.wikipedia.org/wiki/Little_glacial_period

Http://www.fio.vrn.ru/2004/7/index.htm

BBC "Climate Wars" (documentary) 2008

1. How to learn about the climates of the past.
2. Causes of climate change.
4. How to learn about the climates of the past.

There are many ways to make judgments about past, prehistoric climates. One of the most common are:

a) the nature of the fossil animals and plants. So, meeting on the shores of the Aral Sea deposits with imprints of leaves of beech (Fag us Antipofii), oak (Quercus Gmelini), hazel (Corylus insignis), poplar (Populus mutabilis) and other woody plants, we conclude that forests grew here in the Tertiary similar to modern temperate forests. Meanwhile, at present, the shores of the Aral Sea are a desert. In the Lower Tertiary freshwater deposits of Hungary, molluscs related to modern mollusks of the Indomalay archipelago have been found. This, in connection with other data, allows us to assume that the tropical climate then dominated in Central Europe.

A detailed study of organic residues can sometimes provide very valuable data. So, on the fossil leaves of a beech from Germany, belonging to the Tertiary time (namely, to the Miocene), frost damage was found. The existence of winters at this time is also proved by the presence of growth rings in the wood of trees.

b) But it is not only fossils that can be used to draw conclusions about the climates of the past. The same can be judged by the peculiarities of the modern geographical distribution of plants and animals. The sea herring, Clupea harengus, is found in the northern Atlantic and Pacific Oceans, but is absent in the Arctic Ocean east of the Kanin Peninsula, thus avoiding arctic latitudes. Due to this, its spread is interrupted. But, obviously, once its habitat was continuous: from the Atlantic Ocean through the Arctic to the northern part of the Pacific. The extinction of the herring in the intermediate part is obviously due to the cooling that occurred in connection with the Ice Age. The same reason is due to the intermittent distribution of a number of plants that live, on the one hand, in Europe, and on the other, in eastern Asia, and absent in Siberia. This will be discussed in more detail below.

c) The nature of the precipitation often gives an indication of the climate prevailing during the deposition of the sediment. So, having a moraine in front of us, we conclude that this place was once covered by an ice sheet. Finding the loess leads us to conclude that the climate was previously dry. Coal and peat speak of the former dominance of a humid climate.

The study of soils, both modern and ancient, gives extremely interesting results. Here are some examples.

We have just said that loess is formed in a dry climate, But in the Kherson province, as well as in other places, it was found that in the loess layer there is one, and sometimes several layers, each of which is a dark-colored, chernozem-like soil buried under loess sediment. Obviously, during the deposition of this soil, the dry climate changed towards higher humidity.

The Amur region is currently dominated by a moderately humid climate. In accordance with this, the soils belong to the podzolic and boggy types. Podzolic soils are those in which the upper horizons are more or less leached, depleted in bases and sesquioxides (aluminum oxide, iron oxide) and enriched in silica (which makes it seem as if sprinkled with ash); on the contrary, the lower horizons of the podzolic soil are enriched with sesquioxides, manganese oxides, phosphoric acid, and humus. But here's what's great. In the Amur region, in some places under the podzolic soil, clear traces of the soil-forming process have been found, which developed according to a completely different scheme than the podzolic soil; Namely, this fossil soil lying under the podzolic soil turns out to be depleted in silica and enriched in sesquioxides in comparison with the parent rock (lava), that is, it is completely opposite to what is observed in podzolic soil. In some cases, the fossil soil is colored red. In short, we have here before us a weathering of the laterite type, which characterizes countries with a hot climate. It is difficult to determine the exact time when lateritic soils were formed in the Amur region; probably much warmer than now, the climate prevailed here in the Upper Tertiary. It is possible that this era coincided with the spread in Eastern Siberia of the American walnut, Juglans cinerea, the fruits of which were recently found in the sands, in the Aldan valley (a tributary of the Lena), below the mouth of the river. Amgi. Judging by the modern range of the American J. cinereа, as well as J. mandshurica living on the Amur, one can think that the average annual temperature in the lower reaches of the Aldan, when the American walnut grew there, was not lower than 1 ° to 5 ° С. , i.e. 13 ° -17 ° warmer than modern. It can also be noted that at the confluence of the river. Storms in Amur were found the remains of plants Ginkgo and Zeikova, now living in Japan and China, and Zeikova, in addition, in the Caucasus. Finally, it is possible that reef-building corals and tropical molluscs, found in a fossil state at 35 ° N, lived off the coast of Japan (Honzo Island) in the same era. sh., while now reef corals do not go north of 27 ° N here. w (Bonin Islands) - 28 ° 20 "N (Riu-Kiu Islands). Thus, a number of facts support the conclusions drawn from the study of soils.

Another example that clearly illustrates the change in the types of soil formation. In the area of the Chelyabinsk granite massif, modern soils are formed according to the podzolic type, but in some places, for example, on porphyrites, it can be seen that podzolic soils are developed on the ancient weathering crust, in which the soil formation process proceeded according to the lateritic type. There is reason to believe that the time when a warm climate prevailed in the Trans-Urals, which allowed for the formation of laterites, must be attributed to an epoch not later than the Miocene.

d) Finally, changes in climate can be judged by landforms. Thus, kars and trough-shaped valleys in the mountains testify to the former distribution of glaciers in the mountains. The presence of semilunar dunes among the forests, which are often found, for example, in Polesie, speaks of a former desert climate.

2. Causes of climate change.

Climate changes can be: 1) progressive, directed in one direction, 2) periodic, fluctuating within certain limits.

Generally speaking, the climate depends on a number of factors, namely: 1) on the intensity of solar radiation, 2) on the position of the earth in relation to the sun, as well as on the inclination of the ecliptic, 3) on the distribution of land and water, 4) on the height of the land above the level ocean, 5) on the nature of soil and other surface horizons, as well as vegetation, 6) on the composition of the atmosphere and its thickness, 7) on the composition of the hydrosphere (water shell). Finally, it is necessary to mention the influence of the earth's own warmth.

The temperature of the earth's surface rises from the last reason by no more than 0.1 ° C. Thus, the influence of the internal heat of the earth is currently negligible. But the same is true for all periods, starting with the Cambrian. Moreover, even in the preceding Cambrian, Algonquian period, this factor can be disregarded. For the earth's crust, a thickness of already several tens of fathoms is sufficient to be completely protected from the thermal effects of the molten core. In order for the surface of the earth to receive the same amount of heat from its core as it now receives from the sun, molten magma would have to be at a depth of 10 to 30 meters, depending on the rock that composes the earth's crust. And the thickness of only one sedimentary rocks of the Algonquian age in the North. America is estimated at over 9000 meters. This means that already at that time the earth's climates were regulated by the most important radiation of heat from the sun. But, in addition, of course, influenced, as now, by a number of factors: the distribution of land and water, the height of the continents above sea level, the composition of the atmosphere and water envelope, and so on.

Lukashevich draws attention to the following circumstance, which is very important for understanding ancient climates. The thickness of the atmosphere may have varied over geological periods; it can be assumed that since the Archean times, the earth's surface has decreased, due to the cooling of the earth, by 1.5 times, and therefore, the volume of air over a certain area has increased by the same amount, that is, the atmospheric pressure in the Archean time should have been about 500 mm - assuming that the amount of air remains unchanged. And this corresponds to the average height of the continents of about 3300 m. If the solar radiation in the Precambrian time was the same as now, then the decrease in pressure should have led to a very abundant precipitation. Since the Algonquian period is characterized by a very intense manifestation of mountain-forming processes, as a result, powerful glaciers of the Alpine type should have developed.

3. The climates of the geological past.

After these preliminary remarks, we proceed to a review of climates from the earliest times of the geological history of the earth, namely, from the Algonquian period, which preceded the Cambrian. Algonquin period. Very little is known about the climates of this period, since so far a negligible amount of organic remains has been found. Yet one striking fact can be considered established. This is the presence of an extensive ice sheet. In North America, north of Lake Huron, incl. Lower Huronian deposits, discovered (1908) undoubted traces of glaciation in the form of polished and shaded boulders that are part of the so-called. the main conglomerate overlying the Archean rocks. This conglomerate is a formation similar to moraine. The boulders are composed of granites, gneisses, metamorphic schists and Archean igneous rocks. Similar conglomerates, in which, however, no traces of polishing and shading have yet been found, are developed over an enormous extent (over 1000 km) in Canada, in Ontario, reaching a thickness of up to 300 meters. Apparently, the same conglomerates are common in the states of Minnesota and Michigan. The presence of high mountains greatly contributed to the formation of glaciers. The fact that in the Algonquian time a rather cool climate generally prevailed can be judged by the fact that there is very little calcium carbonate in the deposits of this system. And, as you know, in warm seas, there is a very abundant deposition of CaCO 3.

Cambrian period. In the Cambrian, as far as can be judged from the remains of marine fauna, the climate was more or less uniform everywhere. However, some, accepting the displacement of the poles, admit a certain differentiation of zones; in this case, the basis is the distribution of Archaeocyaihidae, peculiar, reef-building organisms, some attributed to sponges, others - to corals.

Be that as it may, for the Cambrian there are clear and numerous traces of glaciation. Back in 1892, Reisch discovered on the shores of the Varanger fiord a moraine dating back to the Lower Cambrian time (Gaisa formation). In China, on Yang-tzu-jiang, at 30 ° n. NS. glacial loams with typical polished and striated boulders were encountered; these deposits are covered with sediments, undoubtedly of Cambrian age. Finally, in southern Australia and Tasmania, the same moraine deposits were found, developed over 450 kilometers between 35 ° and 30 ° S. NS. and 137 ° and 140 ° E. e. Apparently, ice moved in Australia from south to north.

The presence of clear traces of glaciation suggests that a certain differentiation of climates in the Cambrian period, in any case, existed.

Silurian. During the Silurian, the climate throughout the earth was apparently more or less uniform. No glacial deposits are known.

The question is what can cause the uniformity of the climate from the equator to the pole. Indeed, at any intensity of solar radiation and at any tilt of the earth's axis, the amount of heat received by the equator and the poles should be different, and as a result, climatic zones should be found. It should be noted, first of all, that one should speak only of relative uniformity. Thus, Silurian corals from Grinnell's Earth show dwarf growth, indicating that the climatic conditions were not particularly favorable for their development. Greater or lesser climate uniformity may be due, especially for marine fauna, a different distribution of continents and seas, heights and depths, and, consequently, a different distribution of barometric maximums and minimums, winds, currents, etc. Imagine that between Greenland and Europe lies a continuous isthmus; in this case the Golfstrom would not have been able to enter the Barents Sea, and the climate of Murman would have been much more severe; in addition, the said barrier would block the cold polar waters from access to the south, due to which the temperature of the temperate latitudes and the tropics would be higher; thus, the difference between zones under these conditions would be very significant. On the contrary, the destruction of this isthmus would entail a softening of the contrasts between the equator and the pole; the contrast would be even less if temperatures rose to the point where the Greenland ice cap melted. In short, the combination of a number of favorable conditions can lead to the presence of a uniform - to a certain extent - climate.

One more example. With the present position of the earth's axis, the northern hemisphere has winter at perihelion, and the southern hemisphere at aphelion. Consequently, one would have to expect that in the northern hemisphere the difference between winter and summer will be somewhat smoothed out and a more moderate climate will be obtained, on the contrary, and in the southern one - this difference will be increased, strengthening the opposition between summer and winter. In fact, we see the opposite. According to Gann's calculation, the average temperatures in January and July in both hemispheres are as follows:

The annual amplitude in the northern hemisphere is 14.5 °, and in the southern only 7.0 ° - that is, the climate of the southern hemisphere is much more moderate than the northern one: the northern hemisphere has cold winters and hot summers, the southern hemisphere has mild winters and cool summers. The reason is that in the northern hemisphere there is relatively much land and little water, while in the southern hemisphere, water sharply prevails.

Devonian. There is little definite data on the climate of this time. Attention is drawn to the formation conditions of the old red sandstones. Some see them as desert deposits, while others see them as lagoon sediments. In the Lower Devonian deposits of southern Africa, polished and shaded boulders have been found that lie in the moraine. This is the only hint of glacial phenomena in the Devonian.

Carboniferous and Permian periods. The flora of the lower and middle sections of the Carboniferous period shows a very great uniformity everywhere: in the Middle Carboniferous deposits of China, the same plants are found as in Europe. Until recently, there was disagreement about the conditions for the formation of coal. Some believed that coal could only be deposited in humid and temperate climates, based on the fact that peat still forms in the temperate, but not in the tropical zone. Recently, however, extensive peatlands have been discovered in the tropics, in Sumatra. Therefore, they are now inclined to believe that the formation of coal took place in a hot climate (Potonie, Zalessky).

The climate of the Lower and Middle Carboniferous period continued to persist in Western Europe, China, North America, partly in southern Africa, and during the Upper Carboniferous era. But in Australia, southern Africa, Madagascar, India, northern Mongolia, Siberia, in the basin of the Pechora and the northern Dvina, a special flora appears in the Upper Carboniferous and Permian times, some of which are characterized by the ferns Glossoptens and Gangamoptens. The continent on which this flora was distributed, Suess called the Land of Gondwana. It is difficult to say at the present time what reason gave the impetus to the formation of the Gondwana flora. It is possible that its appearance is caused by the differentiation of climatic zones, but there is nothing improbable in the fact that the Gondwana flora originated in the mountains and on high plateaus.

Be that as it may, by the end of the Carboniferous period, there was a significant cooling of the climate. In the southern hemisphere, a very strong glaciation was stated, which is described in more detail below. But it is remarkable that even where traces of glaciation have not yet been observed, there are still clear signs of a cold season (i.e., the climate was not tropical). Woods of the Permian-Carboniferous period with clear annual rings are known both from the Kuznetsk Basin and from the Pechora Territory. For the Permocarbon of the Urals and Donetsk basin (Druzhkovka), Dadoxylon wood with very clear rings has also been described. However, permacarboxylic woods from Brazil are devoid of annual rings, as well as those Dadoxylon from the Donets Basin, which do not originate from Permokarbo-new, but from Upper Carboniferous deposits.

At the end of the Carboniferous or the beginning of the Permian time - precise timing is difficult - intense glaciation covered many parts of the southern hemisphere. Traces of it were found in southern Africa (in the Cape Colony and in the Belgian Congo), India, Australia, Tasmania, and, finally, in southern Brazil and the Falkland Islands. In addition, apparently, there was also glaciation in the area of the eastern slope of the Urals (in the Yekaterinburg district).

In India, glaciation in the basin of the river. Godavari covered an area of at least 0.25 million square meters. km. The boulders here are up to 75 cm in diameter. In the Salt Range, they reach several cubic meters; here, boulder layers are interbedded with marine sediments enclosing organic remains. One might think that here glaciers descended directly into the sea.

In Australia (Victoria), up to ten horizons of boulder deposits (some of which are up to 60 meters thick) have been found in places, interspersed with marine sediments. Obviously, here, as in India (and as now in Greenland and Antarctica), the ice cover ended in the sea. In addition, it is very important that the glaciation here was multiple. The direction of the strokes indicates that the center of the glaciation was southwest of Tasmania. The glacier captured only the southern part of Australia and reached 33.5-34 ° S. NS. (extreme northern limit of distribution) to sea level; here ice mountains broke off from the glacier, which were carried northward by currents to 21-24 ° S. NS.

Traces of Permocarbonic glaciation are especially prominently found in southern Africa, where not only polished and grooved rocks under the moraine were found, but also cliffs worked in exactly the same way as the so-called. lamb foreheads. Moraine deposits, known as the Dwyka conglomerate, extend in southern Africa between 25 ° and 32 ° S. NS. Streaks and lamb foreheads show that the direction of ice movement was from NNE to SSW. And the rocks that make up the boulders were also brought from the north. Gangamopteris leaves have been found in the sandstones covering the Dwyka conglomerate, but no marine sediments covering the glacial ones have been found anywhere.

Permocarbon glaciation in the southern hemisphere occupied an area no less than the Pleistocene glaciation in the northern one. But it is remarkable that a similar glaciation has not yet been found in the northern hemisphere, except for some local ones, for example, along the eastern slope of the Urals. Some believe that the reason for this one-sided glaciation is the uplift of the Gondwana continent, for neither astronomical reasons, nor changes in the composition of the atmosphere can explain the absence of glaciation in the northern hemisphere. So, Koken accepts that in India, in the Aravali region, where traces of intense glaciation of the Permian time were found, heights did not reach 500 m, as now, but over 4000 m.

In Permian time, we meet with reliable traces of deserts. In the Upper Permian sediments, there are significant deposits of rock salt, gypsum and other salts, interspersed with clays and red sandstones. These deposits are undoubtedly marine, but they were formed in a desert climate, similar to those on the shores of Karabugaz.

During the Triassic, a warm and more or less monotonous climate prevailed. The relatively high temperature can be judged by the presence of thick masses of organic limestones in the Middle and Upper Triassic deposits. The uniformity (of course, relative) of the climate is evidenced by the cosmopolitan distribution of many species.

There were no significant differences in climates during the Jurassic. The provinces established (1885) by Neymayr, which he regarded as climatic, have largely facies significance, i.e. due to differences in the physical conditions of the habitat. Still, apparently, colder-water fauna lived at the North Pole. It is remarkable that no trace of the temperate or cold zones in the southern hemisphere could be seen.

It is all the more curious that for the first time in the Lower Cretaceous we meet a more or less sharp climatic differentiation, with which a temperate zone of the southern hemisphere is clearly outlined. Climatic zones are also isolated in the Upper Cretaceous; it is worth mentioning the Mediterranean-equatorial zone, where rudists, corals, nerineas, some typical ammonites, etc. are widespread. ) sporadically there are rudists, but in small forms, indicating unfavorable climatic conditions.

In the Senonian, climatic zones stand out quite clearly due to the distribution in temperate latitudes of belemnites from the genera Belemnitella and Actinocamax, which are absent in the paths. Representatives of the first genus were found in the Upper Cretaceous in Europe, in places in western Asia, in North America (north to Alaska); are absent in the tropics and reappear in the southern hemisphere, in Queensland - in a form close to Belemnitella mucronata.

Traces of glacial phenomena for the Cretaceous period are unknown, except for some indications for Australia, which, however, are refuted by other authors.

Tertiary period. In the Tertiary, as well as in the Cretaceous, the climatic zones were well expressed. It is remarkable that in the Paleocene time (preceding the Eocene in the narrow sense of the word), mollusks characteristic of the boreal seas (Astarte, Axinus, Cyprina, etc.) lived in the seas that covered parts of France and England. Meanwhile, the Paleocene seas of the middle Volga region were much warmer, and the fauna found in the "crustal" Volga region (Lower Saratov stage) even bears a tropical imprint. The Paleocene flora of the Volga region was subtropical; the climate of the country she inhabited was uniformly warm and humid, approximately the same as now in southern Japan, in southeastern China or in the mountains of Java at an altitude of about 2000 meters. Palm trees and ferns, Scitamineae, evergreen oaks, laurel trees, holly grew here. These were evergreen dense forests, among which, however, were found, as now in China or Japan, also forms of a more temperate climate, with falling leaves, such as beech, birch, oak, poplar, ash.

In the Eocene, the tropical type of vegetation already dominates in Europe. But the fact that climatic zones were expressed can be judged by the strong development of nummulites and coral reefs in the Mediterranean-tropical zone and their absence in the northern latitudes (the presence of nummulites in England, Greenland and New Zealand is explained by warm currents). However, in the Eocene, the climatic zones were less sharply differentiated than in the Upper Cretaceous; the climate of Europe was much warmer than today.

In the Oligocene in Europe, cooling again began, but still, along with the forms of a temperate climate, such as willows, poplars, birches, alders, hazels, hornbeams, beeches, chestnuts, grapes, etc., there are also tropical palms, Cinnamomum, breadfruit (Artocarpus ), tree-like lily (Dracaena draco), etc. In Oligocene trees of Central Europe, annual rings are as well expressed as in modern trees. In the Lower Oligocene of the Volyn province. found palms, Sequoia, laurel, along with deciduous trees; the average annual temperature was 16 ° -17 ° C.

In Greenland, in Neogene sediments, representatives of the genera Ginkgo, Taxodium, Libocedrus, G1yptostrobus, Sequoia, Pinus, Liquidambar were found, then poplars, willows, alder, birch, hazel, beeches, chestnuts, oaks, Sassafras, Aralia, ivy, grapes, magnolia, laurel and many others - only 282 species. The same flora was found on Grinnell Earth at 82 ° N. NS. One should not think that this vegetation characterizes a subtropical climate, as Geer believed in his time. It could grow in a humid, temperate climate, which even frosts were not alien to. In southern Chile and along the Strait of Magellan, the dominant trees are evergreen beeches (Nothofagus Dombeyi and N. betuloides), magnolia (Drimus Winteri), cypress (Libocedrus tetragona), and evergreen shrubs. Meanwhile, the climate here is temperate, there is a lot of precipitation, and they are evenly distributed throughout the year, the sky is mostly covered with clouds, snow falls in all seasons, but it does not stay long even in winter. Frosts can also happen at any time of the year, but they are short-lived.

In Central Europe during the Miocene time there was a warm climate (however, with winter frosts); to the north it became more moderate. In general, the Miocene flora of Western Europe resembled the modern flora of the Atlantic states of North. America, southern China and the Caucasus. In France, there were various laurel trees (e.g. Cinnamomum), camphor tree, Myrtus, sequoia, Tahodium, bamboo, dragon tree (Dracaena draco), palms, tree ferns from Os mundaceae. The Sarmatian (Sarmatian is one of the subdivisions of the Miocene) flora of Novorossiya had a quite pronounced character of the modern vegetation of the temperate latitudes of China. These were mainly trees with falling leaves. Chestnuts, hornbeams, maples, nuts, beeches, oaks, etc. grew here, then Zelkova Ungeri, Sapindus, Taxodiumdistichum, Lirio dendron Procaccinii, Ailanthus Confucii, Sterculia tridens, Eucommia ulmoides. The last four forms bring the flora of the Don region, where they were found, close to the East Asian: Eucommia u1 moides now lives in China, in the provinces of Hubei and Sichuan. Ailan thus Confucii is closest to A. glandulosa growing in China, but freely tolerating the climate of Europe. The genus Sterculia is found in China and Japan, Liriodendron - in China and North. America. The Sarmatian flora of the Don region was richer than the modern Transcaucasian one.

Recently, the fauna of Sarmatian land mammals has been discovered in Sevastopol. A representative of the family of giraffes (Achtiaria expectans), antelope Tragoceras, predator Iсtitherium, rhinoceros Ace rarherium Zernowi, and finally Hipparion were found here. All are fauna of a warmer climate than the modern one. At the very end of the Miocene, in the Meotic time, the climate of southern Russia, judging by the finds of fossil plants in southern Bessarabia, again experienced cooling. As far as can be judged from the scarce data, the flora had a rather moderate appearance.

However, we know from Novorossiya the meotic fauna of terrestrial mammals, which characterizes a climate that is warmer than the modern one. So, in the southwest of the Kherson lips. the remains of rhinos (Rhinoceras, Aceratherium), antelopes (Tragoceras), giraffes (CamelopardaIis), then Helladotherium (from the family of giraffes), ostrich, and others were found in meotic deposits. A similar nature, but a much richer fauna is described from the village. Taraclia, Bendery district, in Bessarabia), but it is remarkable that here, among the remains of rhinos, giraffes, antelopes, etc., the remains of a beaver (Castor fiber), an inhabitant of the temperate zone forests, were found.

Cooling progressed during the Pliocene, and at the end of this era, ice accumulations probably formed at the poles. In European Russia, the climate became so mild that the rivers began to be covered with ice in winter.In the southern part of Yekaterinoslavskaya province, along the banks of the Bug estuary, as well as near Odessa, boulders of granite and syenite were found in the Pontic limestones, and in the Kherson lips. (near Odessa, near the colony of Rohrbach), in addition, boulders of Krivoy Rog ferruginous quartzite are located at a considerable distance from their primary deposit, 170-220 versts to the southwest. There are many boulders and they are up to half a meter in size. According to N. A. Sokolov's assumption, these boulders were carried by ice floes along the pontic sea, the waves of which washed the quartzite rocks of the Krivoy Rog region. On the Don, near the village of Nizhnekurmoyarskaya and in other places, in the Upper Pliocene ground deposits, pieces of limestone and other rocks with Carboniferous and Cretaceous fossils were found, brought by river ice from the banks of the Don, from places located much higher than Nizhnekurmoyarskaya.

But at the same time being in Zap. Europe, the remains of a hippopotamus in the Upper Pliocene sediments shows that the climate was still much warmer than the modern one.

The Quaternary period is distinguished by extremely extensive glaciation, which surpassed even the Upper Paleozoic in area. In Europe (and precisely in eastern Europe), the ice sheet descended along the Dnieper to 49 ° N. sh., in America along the Mississippi Valley up to 37.5 °. In the southern hemisphere, traces of this glaciation are known along the entire length of the Andes, starting from the equator, then in southern and tropical Africa, southern Australia, Tasmania, on the southern island of New Zealand, and New Guinea. In the Alps, the Carpathians, in the mountains of the southern peninsulas of Europe, in the Atlas, Asia Minor, the Caucasus, Tien Shan, Altai, Himalayas, Kuenlun there are clear traces of the Ice Age; where there are now glaciers, they once descended much lower; where they are not now, in the ice age they were. In addition to the listed areas of glaciation, there is reason to assume the former spread of glaciers for many more places in East Asia.

As for the reasons that caused the glaciation, there are a lot of hypotheses on this issue that involve astronomical, atmospheric, geomorphological factors, etc. We cannot dwell here on the analysis of all these hypotheses. When assessing them, one must first of all reckon with the fact that glaciations in the Quaternary, like in the Upper Paleozoic, were multiple: so, in the Alps in the Quaternary there were four glaciations, in northern Russia at least two, in North. America to six, etc.

Conclusion. Summarizing everything stated above about the climates of the geological past, we can say that there are four epochs of intense glaciation, namely: 1) Algonquian, 2) Lower Cambrian, 3) Upper Carboniferous and Lower Permian, and 4) post-Pliocene. These are four large climatic waves. Some of these waves, and maybe all of them, in turn, consist of second-order waves. What reasons entailed the onset of ice ages, this, we repeat, is a problem that has not yet been resolved. But one curious circumstance is still emerging. If we compare the epochs of intense glaciation with the epochs of intense mountain building, then it turns out that there is a certain parallelism between them. Following the eras of strong tectonic movements, there is a powerful development of glaciers, as can be seen from the following table:

Intense mountain building.
algonquian
upper silurian
upper carbon
medium chalk
pliocene
Intense glaciation.
algonquian
lower Cambrian
upper carbon and lower. Permian
post-Pliocene.

On the other hand, tectonically calm epochs seem to be distinguished by a more or less uniform climate and the absence of glaciation, as follows: Cambrian (except for the lower), Middle and Upper Devonian, Triassic, Jurassic.

Obviously, the formation of vast and powerful uplifts, under other favorable conditions (for example, in the presence of wet winds, etc.), contributes to the condensation of water vapor and the gradual accumulation of snow and ice. With the passage of time, ice, accumulating, goes beyond the limits of mountain uplifts and covers vast areas. On the contrary, subsidence causes the ice sheet to shrink.

The presence of mountain systems alone does not entail the onset of glaciation. A number of accompanying factors are required, of which the most important is increased precipitation in the mountainous area. The increase in the amount of precipitation can, again, be the result of very diverse reasons. We assume that an increase in precipitation is a consequence of a decrease in temperature, which, in turn, depends on fluctuations in the intensity of solar radiation.