Structure and balance of gases in the atmosphere. Composition of the atmosphere Composition of the earth's atmosphere

Is there really nothing that can regulate the amount of greenhouse gases in the atmosphere? Of course it can. Oxygen does this job perfectly. But the problem is that the planet’s population is growing inexorably, which means that more and more oxygen is being consumed. Our only salvation is vegetation, especially forests. They absorb excess carbon dioxide and release much more oxygen than humans consume.

The greenhouse effect and the Earth's climate

When we talk about the consequences of the greenhouse effect, we understand its impact on the Earth's climate. First of all, this is global warming. Many people equate the concepts of “greenhouse effect” and “global warming”, but they are not equal, but interrelated: the first is the cause of the second.

Global warming is directly related to the oceans. Here is an example of two cause-and-effect relationships.

1. The average temperature of the planet is rising, liquid begins to evaporate. This also applies to the World Ocean: some scientists are afraid that in a couple of hundred years it will begin to “dry up.”
2. At the same time, due to high temperatures, glaciers and sea ice will begin to actively melt in the near future. This will lead to an inevitable rise in sea levels.

We are already seeing regular floods in coastal areas, but if the level of the World Ocean rises significantly, all nearby land areas will be flooded and crops will perish.

Impact on people's lives

Do not forget that an increase in the average temperature of the Earth will affect our lives. The consequences can be very serious. Many areas of our planet, already prone to drought, will become absolutely unviable, people will begin to migrate en masse to other regions. This will inevitably lead to socio-economic problems and the outbreak of the third and fourth world wars. Lack of food, destruction of crops - this is what awaits us in the next century.

But does it have to wait? Or is it still possible to change something? Can humanity reduce the harm from the greenhouse effect?

Actions that can save the Earth

Today, all the harmful factors that lead to the accumulation of greenhouse gases are known, and we know what needs to be done to stop it. Don't think that one person won't change anything. Of course, only all of humanity can achieve the effect, but who knows - maybe a hundred more people are reading a similar article at this moment?

Forest conservation

Stopping deforestation. Plants are our salvation! In addition, it is necessary not only to preserve existing forests, but also to actively plant new ones.

Every person should understand this problem.

Photosynthesis is so powerful that it can provide us with huge amounts of oxygen. It will be enough for the normal life of people and the elimination of harmful gases from the atmosphere.

Use of electric vehicles

Refusal to use fuel-powered vehicles. Every car emits a huge amount of greenhouse gases each year, so why not make a healthier choice for the environment? Scientists are already offering us electric cars - environmentally friendly cars that do not use fuel. The minus of a “fuel” car is another step towards eliminating greenhouse gases. All over the world they are trying to speed up this transition, but so far the modern developments of such machines are far from perfect. Even in Japan, where such cars are used the most, they are not ready to completely switch to their use.

Alternative to hydrocarbon fuels

Invention of alternative energy. Humanity doesn't stand still, so why are we stuck using coal, oil and gas? Burning these natural components leads to the accumulation of greenhouse gases in the atmosphere, so it's time to switch to an environmentally friendly form of energy.

We cannot completely abandon everything that emits harmful gases. But we can help increase oxygen in the atmosphere. Not only a real man should plant a tree - every person must do this!

The atmosphere (from the Greek atmoc - steam and sphere - ball) is the gas (air) shell of the Earth, rotating with it. Life on Earth is possible as long as the atmosphere exists. All living organisms use atmospheric air for breathing; the atmosphere protects from the harmful effects of cosmic rays and temperatures destructive to living organisms, the cold “breath” of space.

Atmospheric air is a mixture of gases that make up the Earth's atmosphere. Air is odorless, transparent, its density is 1.2928 g/l, solubility in water is 29.18 cm~/l, and in the liquid state it acquires a bluish color. Human life is impossible without air, without water and food, but if a person can live without food for several weeks, without water - for several days, then death from suffocation occurs after 4 - 5 minutes.

The main components of the atmosphere are: nitrogen, oxygen, argon and carbon dioxide. In addition to argon, other inert gases are contained in small concentrations. Atmospheric air always contains water vapor (approximately 3 - 4%) and solid particles - dust.

The Earth's atmosphere is divided into the lower (up to 100 km) homosphere with a homogeneous composition of the surface air and the upper hetosphere with a heterogeneous chemical composition. One of the important properties of the atmosphere is the presence of oxygen. There was no oxygen in the Earth's primary atmosphere. Its appearance and accumulation is associated with the spread of green plants and the process of photosynthesis. As a result of the chemical interaction of substances with oxygen, living organisms receive the energy necessary for their life.

Through the atmosphere, the exchange of substances between the Earth and Space takes place, while the Earth receives cosmic dust and meteorites and loses the lightest gases - hydrogen and helium. The atmosphere is permeated with powerful solar radiation, which determines the thermal regime of the planet's surface, causes the dissociation of molecules of atmospheric gases and the ionization of atoms. The vast, thin upper atmosphere consists primarily of ions.

The physical properties and state of the atmosphere change over time: during the day, seasons, years - and in space, depending on the altitude above sea level, latitude, and distance from the ocean.

The structure of the atmosphere

The atmosphere, the total mass of which is 5.15 10" tons, extends upward from the Earth's surface to approximately 3 thousand km. The chemical composition and physical properties of the atmosphere change with altitude, so it is divided into the troposphere, stratosphere, mesosphere, ionosphere (thermosphere) and exosphere.

The bulk of air in the atmosphere (up to 80%) is located in the lower, ground layer - the troposphere. The thickness of the troposphere is on average 11 - 12 km: 8 - 10 km above the poles, 16 - 18 km above the equator. When moving away from the Earth's surface in the troposphere, the temperature decreases by 6 "C per 1 km (Fig. 8). At an altitude of 18 - 20 km, the smooth decrease in temperature stops, it remains almost constant: - 60... - 70 "C. This part of the atmosphere is called the tropopause. The next layer - the stratosphere - occupies a height of 20 - 50 km from the earth's surface. The rest (20%) of the air is concentrated in it. Here the temperature increases with distance from the Earth's surface by 1 - 2 "C per 1 km and in the stratopause at an altitude of 50 - 55 km it reaches 0 "C. Further on, at an altitude of 55-80 km, the mesosphere is located. When moving away from the Earth, the temperature drops by 2 - 3 "C per 1 km, and at an altitude of 80 km, in the mesopause, it reaches - 75... - 90 "C. The thermosphere and exosphere, occupying altitudes of 80 - 1000 and 1000 - 2000 km, respectively, are the most rarefied parts of the atmosphere. Here only individual molecules, atoms and ions of gases are found, the density of which is millions of times less than that of the Earth’s surface. Traces of gases were found up to an altitude of 10 - 20 thousand km.

The thickness of the air shell is relatively small when compared with cosmic distances: it is one-fourth of the radius of the Earth and one ten-thousandth of the distance from the Earth to the Sun. The density of the atmosphere at sea level is 0.001 g/cm~, i.e. a thousand times less than the density of water.

There is a constant exchange of heat, moisture and gases between the atmosphere, the earth's surface and other spheres of the Earth, which, together with the circulation of air masses in the atmosphere, affects the main climate-forming processes. The atmosphere protects living organisms from the powerful flow of cosmic radiation. Every second, a stream of cosmic rays hits the upper layers of the atmosphere: gamma, x-rays, ultraviolet, visible, infrared. If they all reached the earth's surface, they would destroy all life within a few moments.

The ozone screen has the most important protective value. It is located in the stratosphere at an altitude of 20 to 50 km from the Earth's surface. The total amount of ozone (Oz) in the atmosphere is estimated at 3.3 billion tons. The thickness of this layer is relatively small: in total it is 2 mm at the equator and 4 mm at the poles under normal conditions. The maximum concentration of ozone - 8 parts per million parts of air - is located at an altitude of 20 - 25 km.

The main significance of the ozone screen is that it protects living organisms from hard ultraviolet radiation. Part of its energy is spent on the reaction: SO2 ↔ SO3. The ozone screen absorbs ultraviolet rays with a wavelength of about 290 nm or less, so ultraviolet rays, which are beneficial for higher animals and humans and harmful to microorganisms, reach the earth's surface. The destruction of the ozone layer, noticed in the early 1980s, is explained by the use of freons in refrigeration units and the release of aerosols used in everyday life into the atmosphere. Freon emissions in the world then reached 1.4 million tons per year, and the contribution of individual countries to air pollution with freons was: 35% - the USA, 10% each - Japan and Russia, 40% - the EEC countries, 5% - other countries. Coordinated measures have made it possible to reduce the release of freons into the atmosphere. Flights of supersonic aircraft and spacecraft have a devastating impact on the ozone layer.

The atmosphere protects the Earth from numerous meteorites. Every second, up to 200 million meteorites enter the atmosphere, visible to the naked eye, but they burn up in the atmosphere. Small particles of cosmic dust slow down their movement in the atmosphere. About 10" small meteorites fall to the Earth every day. This leads to an increase in the Earth's mass by 1 thousand tons per year. The atmosphere is a heat-insulating filter. Without the atmosphere, the temperature difference on Earth per day would reach 200"C (from 100"C in the afternoon to - 100"C at night).

The relatively constant composition of atmospheric air in the troposphere is of greatest importance for all living organisms. The balance of gases in the atmosphere is maintained due to the constantly ongoing processes of their use by living organisms and the release of gases into the atmosphere. Nitrogen is released during powerful geological processes (volcanic eruptions, earthquakes) and during the decomposition of organic compounds. Nitrogen is removed from the air due to the activity of nodule bacteria.

However, in recent years there has been a change in the balance of nitrogen in the atmosphere due to human economic activities. Nitrogen fixation during the production of nitrogen fertilizers has significantly increased. It is assumed that the volume of industrial nitrogen fixation will increase significantly in the near future and exceed its release into the atmosphere. Nitrogen fertilizer production is projected to double every 6 years. This meets the growing agricultural needs for nitrogen fertilizers. However, the issue of compensation for nitrogen removal from atmospheric air remains unresolved. However, due to the huge total amount of nitrogen in the atmosphere, this problem is not as serious as the balance of oxygen and carbon dioxide.

About 3.5 - 4 billion years ago, the oxygen content in the atmosphere was 1000 times less than now, since there were no main oxygen producers - green plants. The current ratio of oxygen and carbon dioxide is maintained by the vital activity of living organisms. As a result of photosynthesis, green plants consume carbon dioxide and release oxygen. It is used for respiration by all living organisms. The natural processes of consumption of CO3 and O2 and their release into the atmosphere are well balanced.

With the development of industry and transport, oxygen is used in combustion processes in ever increasing quantities. For example, during one transatlantic flight, a jet plane burns 35 tons of oxygen. A passenger car consumes the daily oxygen requirement of one person per 1.5 thousand kilometers (on average, a person consumes 500 liters of oxygen per day, passing 12 tons of air through the lungs). According to experts, the combustion of various types of fuel now requires from 10 to 25% of the oxygen produced by green plants. The supply of oxygen to the atmosphere is decreasing due to a reduction in the areas of forests, savannas, steppes and an increase in desert areas, the growth of cities, and transport highways. The number of oxygen producers among aquatic plants is decreasing due to pollution of rivers, lakes, seas and oceans. It is believed that in the next 150 - 180 years the amount of oxygen in the atmosphere will be reduced by a third compared to its current content.

The use of oxygen reserves is increasing at the same time as an equivalent increase in the release of carbon dioxide into the atmosphere. According to the UN, over the past 100 years the amount of CO~ in the Earth's atmosphere has increased by 10 - 15%. If the intended trend continues, then in the third millennium the amount of CO~ in the atmosphere may increase by 25%, i.e. from 0.0324 to 0.04% of the volume of dry atmospheric air. A slight increase in carbon dioxide in the atmosphere has a positive effect on the productivity of agricultural plants. Thus, when the air in greenhouses is saturated with carbon dioxide, the yield of vegetables increases due to the intensification of the process of photosynthesis. However, with increasing COz in the atmosphere, complex global problems arise, which will be discussed below.

The atmosphere is one of the main meteorological and climate-forming factors. The climate-forming system includes the atmosphere, ocean, land surface, cryosphere and biosphere. The mobility and inertial characteristics of these components are different; they have different reaction times to external disturbances in adjacent systems. Thus, for the atmosphere and land surface, the response time is several weeks or months. The atmosphere is associated with circulation processes of moisture and heat transfer and cyclonic activity.

The greenhouse effect in the atmosphere of our planet is caused by the fact that the flow of energy in the infrared range of the spectrum, rising from the surface of the Earth, is absorbed by the molecules of atmospheric gases and radiated back in different directions, as a result, half of the energy absorbed by the molecules of greenhouse gases returns back to the surface of the Earth, causing it warming up It should be noted that the greenhouse effect is a natural atmospheric phenomenon (Fig. 5). If there were no greenhouse effect on Earth at all, then the average temperature on our planet would be about -21°C, but thanks to greenhouse gases, it is +14°C. Therefore, purely theoretically, human activity associated with the release of greenhouse gases into the Earth’s atmosphere should lead to further heating of the planet. The main greenhouse gases, in order of their estimated impact on the Earth's heat balance, are water vapor (36-70%), carbon dioxide (9-26%), methane (4-9%), halocarbons, nitric oxide.

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Coal-fired power plants, factory chimneys, car exhaust and other human-made pollution sources together emit about 22 billion tons of carbon dioxide and other greenhouse gases into the atmosphere each year. Livestock farming, fertilizer use, coal combustion and other sources produce about 250 million tons of methane per year. About half of all greenhouse gases emitted by humanity remain in the atmosphere. About three-quarters of all anthropogenic greenhouse gas emissions over the past 20 years are caused by the use of oil, natural gas and coal (Figure 6). Much of the rest is caused by changes in the landscape, primarily deforestation.

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water vapor- the most important greenhouse gas today. However, water vapor is also involved in many other processes, which makes its role far ambiguous in different conditions.

First of all, during evaporation from the Earth's surface and further condensation in the atmosphere, up to 40% of all heat entering the atmosphere is transferred to the lower layers of the atmosphere (troposphere) due to convection. Thus, when water vapor evaporates, it slightly lowers the surface temperature. But the heat released as a result of condensation in the atmosphere goes to warm it up, and subsequently, to warm up the surface of the Earth itself.

But after the condensation of water vapor, water droplets or ice crystals are formed, which intensively participate in the processes of scattering sunlight, reflecting part of the solar energy back into space. Clouds, which are just accumulations of these droplets and crystals, increase the share of solar energy (albedo) reflected by the atmosphere itself back into space (and then precipitation from the clouds can fall in the form of snow, increasing the albedo of the surface).

However, water vapor, even condensed into droplets and crystals, still has powerful absorption bands in the infrared region of the spectrum, which means the role of the same clouds is far from clear. This duality is especially noticeable in the following extreme cases - when the sky is covered with clouds in sunny summer weather, the surface temperature decreases, and if the same thing happens on a winter night, then, on the contrary, it increases. The final result is also influenced by the position of the clouds - at low altitudes, thick clouds reflect a lot of solar energy, and the balance may in this case be in favor of the anti-greenhouse effect, but at high altitudes, thin cirrus clouds transmit quite a lot of solar energy downwards, but even thin clouds are almost insurmountable obstacles to infrared radiation and, and here we can talk about the predominance of the greenhouse effect.

Another feature of water vapor - a humid atmosphere to some extent contributes to the binding of another greenhouse gas - carbon dioxide, and its transfer by rainfall to the Earth's surface, where, as a result of further processes, it can be consumed in the formation of carbonates and combustible minerals.

Human activity has a very weak direct effect on the content of water vapor in the atmosphere - only due to the increase in the area of ​​irrigated land, changes in the area of ​​swamps and the work of energy, which is negligible against the background of evaporation from the entire water surface of the Earth and volcanic activity. Because of this, quite often little attention is paid to it when considering the problem of the greenhouse effect.

However, the indirect effect on water vapor content can be very large, due to feedbacks between atmospheric water vapor content and warming caused by other greenhouse gases, which we will now consider.

It is known that as the temperature increases, the evaporation of water vapor also increases, and for every 10 °C the possible content of water vapor in the air almost doubles. For example, at 0 °C the saturated vapor pressure is about 6 MB, at +10 °C - 12 MB, and at +20 °C - 23 MB.

It can be seen that the content of water vapor strongly depends on temperature, and when it decreases for some reason, firstly, the greenhouse effect of water vapor itself decreases (due to the decreased content), and secondly, condensation of water vapor occurs, which, of course, strongly inhibits the decrease in temperature due to the release of condensation heat, but after condensation, the reflection of solar energy increases, both in the atmosphere itself (scattering on droplets and ice crystals) and on the surface (snowfall), which further lowers the temperature.

As the temperature rises, the content of water vapor in the atmosphere increases, its greenhouse effect increases, which intensifies the initial increase in temperature. In principle, cloudiness is also increasing (more water vapor enters relatively cold areas), but extremely weakly - according to I. Mokhov, about 0.4% per degree of warming, which cannot greatly affect the increase in the reflection of solar energy.

Carbon dioxide- the second largest contributor to the greenhouse effect today, does not freeze out when the temperature drops, and continues to create a greenhouse effect even at the lowest temperatures possible in terrestrial conditions. Probably, it was precisely thanks to the gradual accumulation of carbon dioxide in the atmosphere as a result of volcanic activity that the Earth was able to emerge from the state of powerful glaciations (when even the equator was covered with a thick layer of ice), into which it fell at the beginning and end of the Proterozoic.

Carbon dioxide is involved in a powerful carbon cycle in the lithosphere-hydrosphere-atmosphere system, and changes in the earth's climate are associated primarily with changes in the balance of its entry into and removal from the atmosphere.

Due to the relatively high solubility of carbon dioxide in water, the content of carbon dioxide in the hydrosphere (primarily the oceans) is now 4x104 Gt (gigatons) of carbon (from here on, data on CO2 in terms of carbon are given), including deep layers (Putvinsky, 1998). The atmosphere currently contains about 7.5x102 Gt of carbon (Alekseev et al., 1999). The CO2 content in the atmosphere was not always low - for example, in the Archean (about 3.5 billion years ago) the atmosphere consisted of almost 85-90% carbon dioxide, at significantly higher pressure and temperature (Sorokhtin, Ushakov, 1997). However, the supply of significant masses of water to the Earth’s surface as a result of degassing of the interior, as well as the emergence of life, ensured the binding of almost all atmospheric and a significant part of carbon dioxide dissolved in water in the form of carbonates (about 5.5x107 Gt of carbon is stored in the lithosphere (IPCC report, 2000)) . Also, carbon dioxide began to be converted by living organisms into various forms of combustible minerals. In addition, the sequestration of part of the carbon dioxide also occurred due to the accumulation of biomass, the total carbon reserves in which are comparable to those in the atmosphere, and taking into account the soil, they are several times higher.

However, we are primarily interested in the flows that supply carbon dioxide into the atmosphere and remove it from it. The lithosphere now provides a very small flow of carbon dioxide entering the atmosphere primarily due to volcanic activity - about 0.1 Gt of carbon per year (Putvinsky, 1998). Significantly large flows are observed in the ocean (together with the organisms living there) - atmosphere, and terrestrial biota - atmosphere systems. About 92 Gt of carbon enters the ocean annually from the atmosphere and 90 Gt returns back to the atmosphere (Putvinsky, 1998). Thus, the ocean annually removes about 2 Gt of carbon from the atmosphere. At the same time, during the processes of respiration and decomposition of terrestrial dead living beings, about 100 Gt of carbon per year enters the atmosphere. In the processes of photosynthesis, terrestrial vegetation also removes about 100 Gt of carbon from the atmosphere (Putvinsky, 1998). As we can see, the mechanism of carbon intake and removal from the atmosphere is quite balanced, providing approximately equal flows. Modern human activity includes in this mechanism an ever-increasing additional flow of carbon into the atmosphere due to the combustion of fossil fuels (oil, gas, coal, etc.) - according to data, for example, for the period 1989-99, an average of about 6.3 Gt in year. Also, the flow of carbon into the atmosphere increases due to deforestation and partial burning of forests - up to 1.7 Gt per year (IPCC report, 2000), while the increase in biomass contributing to the absorption of CO2 is only about 0.2 Gt per year instead of almost 2 Gt in year. Even taking into account the possibility of absorption of about 2 Gt of additional carbon by the ocean, there still remains a fairly significant additional flow (currently about 6 Gt per year), increasing the carbon dioxide content in the atmosphere. In addition, the absorption of carbon dioxide by the ocean may decrease in the near future, and even the reverse process is possible - the release of carbon dioxide from the World Ocean. This is due to a decrease in the solubility of carbon dioxide with increasing water temperature - for example, when the water temperature increases from just 5 to 10 ° C, the solubility coefficient of carbon dioxide in it decreases from approximately 1.4 to 1.2.

So, the flow of carbon dioxide into the atmosphere caused by economic activities is not large compared to some natural flows, but its uncompensation leads to the gradual accumulation of CO2 in the atmosphere, which destroys the balance of CO2 input and output that has developed over billions of years of the evolution of the Earth and life on it.

Numerous facts from the geological and historical past indicate a connection between climate change and fluctuations in greenhouse gases. In the period from 4 to 3.5 billion years ago, the brightness of the Sun was about 30% less than it is now. However, even under the rays of the young, “pale” Sun, life developed on Earth and sedimentary rocks formed: at least on part of the earth’s surface, the temperature was above the freezing point of water. Some scientists suggest that at that time the earth's atmosphere contained 1000 times more axis carbon dioxide than now, and this compensated for the lack of solar energy, since more of the heat emitted by the Earth remained in the atmosphere. The increasing greenhouse effect could be one of the reasons for the exceptionally warm climate later in the Mesozoic era (the age of dinosaurs). According to an analysis of fossil remains, the Earth at that time was 10-15 degrees warmer than it is now. It should be noted that then, 100 million years ago and earlier, the continents occupied a different position than in our time, and the oceanic circulation was also different, so the transfer of heat from the tropics to the polar regions could be greater. However, calculations by Eric J. Barron, now at the University of Pennsylvania, and other researchers indicate that paleocontinental geography may have accounted for no more than half of the Mesozoic warming. The remainder of the warming can easily be explained by rising carbon dioxide levels. This assumption was first put forward by Soviet scientists A. B. Ronov from the State Hydrological Institute and M. I. Budyko from the Main Geophysical Observatory. Calculations supporting this proposal were carried out by Eric Barron, Starley L. Thompson of the National Center for Atmospheric Research (NCAR). From a geochemical model developed by Robert A. Berner and Antonio C. Lasaga of Yale University and the late Robert. Fields in Texas turned into desert after a drought lasted for some time in 1983. This picture, as calculations using computer models show, can be observed in many places if, as a result of global warming, soil moisture in the central regions of the continents decreases, where grain production is concentrated.

M. Garrels of the University of South Florida, it follows that carbon dioxide could be released during exceptionally strong volcanic activity at mid-ocean ridges, where rising magma forms new ocean floor. Direct evidence pointing to a connection during glaciations between atmospheric greenhouse gases and climate can be “extracted” from air bubbles included in Antarctic ice, which formed in ancient times as a result of the compaction of falling snow. A team of researchers led by Claude Laurieux from the Laboratory of Glaciology and Geophysics in Grenoble studied a 2000 m long ice column (corresponding to a period of 160 thousand years) obtained by Soviet researchers at the Vostok station in Antarctica. Laboratory analysis of the gases contained in this column of ice showed that in the ancient atmosphere, the concentrations of carbon dioxide and methane changed in concert and, more importantly, “in time” with changes in the average local temperature (it was determined by the ratio of the concentrations of hydrogen isotopes in water molecules ). During the last interglacial period, which lasted for 10 thousand years, and during the interglacial period preceding it (130 thousand years ago), which also lasted 10 thousand years, the average temperature in this area was 10 degrees higher than during the glaciations. (In general, the Earth was 5 os warmer during these periods.) During these same periods, the atmosphere contained 25% more carbon dioxide and 100,070 more methane than during the glaciations. It is unclear whether changes in greenhouse gases were the cause and climate change the consequence, or vice versa. Most likely, the cause of glaciations were changes in the Earth's orbit and the special dynamics of the advance and retreat of glaciers; however, these climatic fluctuations may have been amplified by changes in biota and fluctuations in ocean circulation that influence the content of greenhouse gases in the atmosphere. Even more detailed data on greenhouse gas fluctuations and climate change are available for the last 100 years, during which there has been a further increase of 25% in carbon dioxide concentrations and 100% in methane. The average global temperature "record" for the past 100 years was examined by two teams of researchers, led by James E. Hansen of the National Aeronautics and Space Administration's Goddard Institute for Space Studies, and T. M. L. Wigley of the Climate Division of Eastern University. England.

Heat retention by the atmosphere is the main component of the Earth's energy balance (Fig. 8). Approximately 30% of the energy coming from the Sun is reflected (left) from either clouds, particles, or the Earth's surface; the remaining 70% is absorbed. The absorbed energy is re-radiated in the infrared by the surface of the planet.

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These scientists used measurements from weather stations scattered across all continents (the Climate Division team also included measurements at sea in the analysis). At the same time, the two groups adopted different methods for analyzing observations and taking into account “distortions” associated, for example, with the fact that some weather stations “moved” to another place over a hundred years, and some located in cities gave data that were “contaminated” » the influence of heat generated by industrial enterprises or accumulated during the day by buildings and pavements. The latter effect, leading to the emergence of heat islands, is very noticeable in developed countries, such as the United States. However, even if the correction calculated for the United States (it was obtained by Thomas R. Karl of the National Climatic Data Center in Asheville, North Carolina, and P. D. Jones of the University of East Anglia) is extended to all data on the globe, in both entries it will remain “<реальное» потепление величиной 0,5 О С, относящееся к последним 100 годам. В согласии с общей тенденцией 1980-е годы остаются самым теплым десятилетием, а 1988, 1987 и 1981 гг. - наиболее теплыми годами (в порядке перечисления). Можно ли считать это «сигналом» парникового потепления? Казалось бы, можно, однако в действительности факты не столь однозначны. Возьмем для примера такое обстоятельство: вместо неуклонного потепления, какое можно ожидать от парникового эффекта, быстрое повышение температуры, происходившее до конца второй мировой войны, сменилось небольшим похолоданием, продлившимся до середины 1970-х годов, за которым последовал второй период быстрого потепления, продолжающийся по сей день. Какой характер примет изменение температуры в ближайшее время? Чтобы дать такой прогноз, необходимо ответить на три вопроса. Какое количество диоксида углерода и других парниковых газов будет выброшено в атмосферу? Насколько при этом возрастет концентрация этих газов в атмосфере? Какой климатический эффект вызовет это повышение концентрации, если будут действовать естественные и антропогенные факторы, которые могут ослаблять или усиливать климатические изменения? Прогноз выбросов - нелегкая задача для исследователей, занимающихся анализом человеческой деятельности. Какое количество диоксида углерода попадет в атмосферу, зависит главным образом от того, сколько ископаемого топлива будет сожжено и сколько лесов вырублено (последний фактор ответствен за половину прироста парниковых газов с 1800 г. и за 20070прироста в наше время). И тот и другой фактор зависят в свою очередь от множества причин. Так, на потреблении ископаемого топлива сказываются рост населения, переход к альтернативным источникам энергии и меры по экономии энергии, а также состояние мировой экономики. Прогнозы в основном сводятся к тому, что потребление ископаемого топлива на земном шаре в целом будет увеличиваться примерно с той же скоростью, что и сегодня намного медленнее, чем до энергетического кризиса 1970-х годов. В результате эмиссия (поступление в атмосферу) диоксида углерода в ближайшие несколько десятилетий, будет увеличиваться на 0,5-2070 в год. Другие парниковые газы, такие как ХФУ, оксиды азота и тропосферный озон, могут вносить в потепление климата почти столь же большой вклад, что и диоксид углерода, хотя в атмосферу их попадает значительно меньше: объясняется это тем, что они более эффективно поглощают солнечную радиацию. Предсказать, какова будет эмиссия этих газов - задача еще более трудная. Так, например, не вполне ясно происхождение некоторых газов, в частности метана; величина выбросов других газов, таких как ХФУ или озон, будет зависеть от того, какие изменения в технологии и политике произойдут в ближайшем будущем.

Exchange of carbon between the atmosphere and various “reservoirs” on Earth (Fig. 9). Each number indicates, in billions of tons, the inflow or outflow of carbon (in the form of dioxide) per year or its stock in the reservoir. These natural cycles, one on land and the other on ocean, remove as much carbon dioxide from the atmosphere as it adds, but human activity such as deforestation and the burning of fossil fuels causes carbon levels to fall in the atmosphere increases annually by 3 billion tons. Data taken from the work of Bert Bohlin at Stockholm University

Fig.9

Let's assume we have a reasonable forecast of how carbon dioxide emissions will change. What changes in this case will occur with the concentration of this gas in the atmosphere? Atmospheric carbon dioxide is “consumed” by plants, as well as by the ocean, where it is used up in chemical and biological processes. As the concentration of atmospheric carbon dioxide changes, the rate of “consumption” of this gas will likely change. In other words, the processes that cause changes in the content of atmospheric carbon dioxide must include feedback. Carbon dioxide is the "feedstock" for photosynthesis in plants, so its consumption by plants will likely increase as it accumulates in the atmosphere, which will slow down this accumulation. Likewise, since the content of carbon dioxide in surface ocean waters is in approximately equilibrium with its content in the atmosphere, increasing the uptake of carbon dioxide by ocean water will slow its accumulation in the atmosphere. It may happen, however, that the accumulation of carbon dioxide and other greenhouse gases in the atmosphere will trigger positive feedback mechanisms that will increase the climate effect. Thus, rapid climate change may lead to the disappearance of some forests and other ecosystems, which will weaken the ability of the biosphere to absorb carbon dioxide. Moreover, warming can lead to the rapid release of carbon stored in dead organic matter in the soil. This carbon, which is twice as much as in the atmosphere, is continually converted into carbon dioxide and methane by soil bacteria. Warming may speed up their operation, resulting in increased release of carbon dioxide (from dry soils) and methane (from rice fields, landfills and wetlands). Quite a lot of methane is also stored in sediments on the continental shelf and below the permafrost layer in the Arctic in the form of clathrates - molecular lattices consisting of methane and water molecules. Warming of shelf waters and thawing of permafrost can lead to the release of methane. Despite these uncertainties, Many researchers believe that the absorption of carbon dioxide by plants and the ocean will slow the accumulation of this gas in the atmosphere - at least in the next 50 to 100 years. Typical estimates based on current emission rates indicate that of the total amount of carbon dioxide entering. into the atmosphere, about half will remain there. It follows that carbon dioxide concentrations will double from 1900 levels (to 600 ppm) between about 2030 and 2080. However, other greenhouse gases will likely accumulate in the atmosphere faster.

Greenhouse gases

Greenhouse gases are gases that are believed to cause the global greenhouse effect.

The main greenhouse gases, in order of their estimated impact on the Earth's thermal balance, are water vapor, carbon dioxide, methane, ozone, halocarbons and nitrous oxide.

water vapor

Water vapor is the main natural greenhouse gas, responsible for more than 60% of the effect. Direct anthropogenic impact on this source is insignificant. At the same time, an increase in the Earth's temperature caused by other factors increases evaporation and the total concentration of water vapor in the atmosphere at almost constant relative humidity, which in turn increases the greenhouse effect. Thus, some positive feedback occurs.

Methane

A gigantic eruption of methane accumulated under the seabed 55 million years ago warmed the Earth by 7 degrees Celsius.

The same thing can happen now - this assumption was confirmed by researchers from NASA. Using computer simulations of ancient climates, they tried to better understand the role of methane in climate change. Currently, most research on the greenhouse effect focuses on the role of carbon dioxide in this effect, although the potential of methane to retain heat in the atmosphere is 20 times greater than that of carbon dioxide.

A variety of gas-powered household appliances are contributing to the increase in methane levels in the atmosphere.

Over the past 200 years, methane in the atmosphere has more than doubled due to decomposition of organic matter in swamps and wet lowlands, as well as leaks from man-made objects such as gas pipelines, coal mines, increased irrigation and off-gassing from livestock. But there is another source of methane - decaying organic matter in ocean sediments, preserved frozen under the seabed.

Typically, low temperatures and high pressure keep methane under the ocean in a stable state, but this was not always the case. During periods of global warming, such as the late Paleocene Thermal Maximum, which occurred 55 million years ago and lasted for 100 thousand years, the movement of lithospheric plates, particularly in the Indian subcontinent, led to a drop in pressure on the seafloor and could cause a large release of methane. As the atmosphere and ocean began to warm, methane emissions could increase. Some scientists believe that current global warming could lead to the same scenario - if the ocean warms up significantly.

When methane enters the atmosphere, it reacts with oxygen and hydrogen molecules to create carbon dioxide and water vapor, each of which can cause the greenhouse effect. According to previous forecasts, all emitted methane will turn into carbon dioxide and water in about 10 years. If this is true, then increasing carbon dioxide concentrations will be the main cause of warming of the planet. However, attempts to confirm the reasoning with references to the past were unsuccessful - no traces of an increase in carbon dioxide concentration 55 million years ago were found.

The models used in the new study showed that when the level of methane in the atmosphere sharply increases, the content of oxygen and hydrogen reacting with methane in it decreases (until the reaction stops), and the remaining methane remains in the air for hundreds of years, itself becoming a cause of global warming. And these hundreds of years are enough to warm up the atmosphere, melt the ice in the oceans and change the entire climate system.

The main anthropogenic sources of methane are digestive fermentation in livestock, rice growing, and biomass burning (including deforestation). Recent studies have shown that a rapid increase in atmospheric methane concentrations occurred in the first millennium AD (presumably as a result of the expansion of agricultural and livestock production and forest burning). Between 1000 and 1700, methane concentrations fell by 40%, but began to rise again in recent centuries (presumably as a result of the expansion of arable land and pastures and forest burning, the use of wood for heating, increased numbers of livestock, sewage, and rice cultivation) . Some contribution to the supply of methane comes from leaks during the development of coal and natural gas deposits, as well as the emission of methane as part of biogas generated at waste disposal sites

Carbon dioxide

Sources of carbon dioxide in the Earth's atmosphere are volcanic emissions, vital activity of organisms, and human activity. Anthropogenic sources include the combustion of fossil fuels, the burning of biomass (including deforestation), and some industrial processes (for example, cement production). The main consumers of carbon dioxide are plants. Normally, the biocenosis absorbs approximately the same amount of carbon dioxide as it produces (including through biomass decay).

The influence of carbon dioxide on the intensity of the greenhouse effect.

Much still needs to be learned about the carbon cycle and the role of the world's oceans as a vast reservoir of carbon dioxide. As mentioned above, every year humanity adds 7 billion tons of carbon in the form of CO 2 to the existing 750 billion tons. But only about half of our emissions - 3 billion tons - remain in the air. This can be explained by the fact that most CO 2 is used by terrestrial and marine plants, buried in marine sediments, absorbed by seawater, or otherwise absorbed. Of this large portion of CO 2 (about 4 billion tons), the ocean absorbs about two billion tons of atmospheric carbon dioxide each year.

All this increases the number of unanswered questions: How exactly does sea water interact with atmospheric air, absorbing CO 2? How much more carbon can the seas absorb, and what level of global warming might affect their capacity? What is the capacity of the oceans to absorb and store heat trapped by climate change?

The role of clouds and suspended particles in air currents called aerosols is not easy to take into account when building a climate model. Clouds shade the earth's surface, leading to cooling, but depending on their height, density and other conditions, they can also trap heat reflected from the earth's surface, increasing the intensity of the greenhouse effect. The effect of aerosols is also interesting. Some of them alter water vapor, condensing it into small droplets that form clouds. These clouds are very dense and obscure the Earth's surface for weeks. That is, they block sunlight until they fall with precipitation.

The combined effect can be enormous: the 1991 eruption of Mount Pinatuba in the Philippines released a colossal volume of sulfates into the stratosphere, causing a worldwide drop in temperature that lasted two years.

Thus, our own pollution, mainly caused by burning sulfur-containing coal and oils, may temporarily offset the effects of global warming. Experts estimate that aerosols reduced the amount of warming by 20% during the 20th century. In general, temperatures have been rising since the 1940s, but have fallen since 1970. The aerosol effect may help explain the anomalous cooling in the middle of the last century.

In 2006, carbon dioxide emissions into the atmosphere amounted to 24 billion tons. A very active group of researchers argues against the idea that human activity is one of the causes of global warming. In her opinion, the main thing is the natural processes of climate change and increased solar activity. But, according to Klaus Hasselmann, head of the German Climatological Center in Hamburg, only 5% can be explained by natural causes, and the remaining 95% is a man-made factor caused by human activity.

Some scientists also do not connect the increase in CO 2 with an increase in temperature. Skeptics say that if rising temperatures are to be blamed on rising CO 2 emissions, temperatures must have risen during the post-war economic boom, when fossil fuels were burned in huge quantities. However, Jerry Mallman, director of the Geophysical Fluid Dynamics Laboratory, calculated that increased use of coal and oils rapidly increased the sulfur content in the atmosphere, causing cooling. After 1970, the thermal effect of the long life cycles of CO 2 and methane suppressed rapidly decaying aerosols, causing temperatures to rise. Thus, we can conclude that the influence of carbon dioxide on the intensity of the greenhouse effect is enormous and undeniable.

However, the increasing greenhouse effect may not be catastrophic. Indeed, high temperatures may be welcome where they are quite rare. Since 1900, the greatest warming has been observed from 40 to 70 0 northern latitude, including Russia, Europe, and the northern part of the United States, where industrial emissions of greenhouse gases began earliest. Most of the warming occurs at night, primarily due to increased cloud cover, which traps outgoing heat. As a result, the sowing season was extended by a week.

Moreover, the greenhouse effect may be good news for some farmers. High concentrations of CO 2 can have a positive effect on plants because plants use carbon dioxide during photosynthesis, converting it into living tissue. Therefore, more plants mean more absorption of CO 2 from the atmosphere, slowing down global warming.

This phenomenon was studied by American specialists. They decided to create a model of the world with double the amount of CO 2 in the air. To do this, they used fourteen-year-old pine forest in Northern California. Gas was pumped through pipes installed among the trees. Photosynthesis increased by 50-60%. But the effect soon became the opposite. The suffocating trees could not cope with such volumes of carbon dioxide. The advantage in the process of photosynthesis was lost. This is another example of how human manipulation leads to unexpected results.

But these small positive aspects of the greenhouse effect cannot be compared with the negative ones. Take, for example, the experience with a pine forest, where the volume of CO 2 was doubled, and by the end of this century the concentration of CO 2 is predicted to quadruple. One can imagine how catastrophic the consequences could be for plants. And this, in turn, will increase the volume of CO 2, since the fewer plants, the greater the concentration of CO 2.

Consequences of the greenhouse effect

greenhouse effect gases climate

As temperatures rise, the evaporation of water from oceans, lakes, rivers, etc. will increase. Since warmer air can hold more water vapor, this creates a powerful feedback effect: the warmer it gets, the higher the water vapor content in the air, which in turn increases the greenhouse effect.

Human activity has little effect on the amount of water vapor in the atmosphere. But we emit other greenhouse gases, which makes the greenhouse effect more and more intense. Scientists believe that increasing CO 2 emissions, mostly from burning fossil fuels, explain at least about 60% of the Earth's warming since 1850. The concentration of carbon dioxide in the atmosphere is increasing by about 0.3% per year, and is now about 30% higher than before the industrial revolution. If we express this in absolute terms, then every year humanity adds approximately 7 billion tons. Despite the fact that this is a small part in relation to the total amount of carbon dioxide in the atmosphere - 750 billion tons, and even smaller compared to the amount of CO 2 contained in the World Ocean - approximately 35 trillion tons, it remains very significant. Reason: natural processes are in equilibrium, such a volume of CO 2 enters the atmosphere, which is removed from there. And human activity only adds CO 2.

The atmosphere is the air envelope of the Earth. Extending up to 3000 km from the earth's surface. Its traces can be traced to altitudes of up to 10,000 km. A. has an uneven density 50 5 its masses are concentrated up to 5 km, 75% - up to 10 km, 90% - up to 16 km.

The atmosphere consists of air - a mechanical mixture of several gases.

Nitrogen(78%) in the atmosphere plays the role of an oxygen diluent, regulating the rate of oxidation, and, consequently, the speed and intensity of biological processes. Nitrogen is the main element of the earth’s atmosphere, which continuously exchanges with living matter of the biosphere, and the constituent parts of the latter are nitrogen compounds (amino acids, purines, etc.). Nitrogen is extracted from the atmosphere by inorganic and biochemical routes, although they are closely interrelated. Inorganic extraction is associated with the formation of its compounds N 2 O, N 2 O 5, NO 2, NH 3. They are found in precipitation and are formed in the atmosphere under the influence of electrical discharges during thunderstorms or photochemical reactions under the influence of solar radiation.

Biological fixation of nitrogen is carried out by some bacteria in symbiosis with higher plants in soils. Nitrogen is also fixed by some plankton microorganisms and algae in the marine environment. In quantitative terms, the biological fixation of nitrogen exceeds its inorganic fixation. The exchange of all nitrogen in the atmosphere occurs within approximately 10 million years. Nitrogen is found in gases of volcanic origin and in igneous rocks. When various samples of crystalline rocks and meteorites are heated, nitrogen is released in the form of N 2 and NH 3 molecules. However, the main form of the presence of nitrogen, both on Earth and on the terrestrial planets, is molecular. Ammonia, entering the upper atmosphere, quickly oxidizes, releasing nitrogen. In sedimentary rocks it is buried together with organic matter and is found in increased quantities in bituminous deposits. During regional metamorphism of these rocks, nitrogen is released in various forms into the Earth's atmosphere.

Geochemical nitrogen cycle (

Oxygen(21%) is used by living organisms for respiration and is part of organic matter (proteins, fats, carbohydrates). Ozone O 3. delays life-destructive ultraviolet radiation from the Sun.

Oxygen is the second most widespread gas in the atmosphere, playing an extremely important role in many processes in the biosphere. The dominant form of its existence is O 2. In the upper layers of the atmosphere, under the influence of ultraviolet radiation, dissociation of oxygen molecules occurs, and at an altitude of approximately 200 km, the ratio of atomic oxygen to molecular (O: O 2) becomes equal to 10. When these forms of oxygen interact in the atmosphere (at an altitude of 20-30 km), a ozone belt (ozone screen). Ozone (O 3) is necessary for living organisms, blocking most of the ultraviolet radiation from the Sun, which is harmful to them.

In the early stages of the Earth's development, free oxygen appeared in very small quantities as a result of photodissociation of carbon dioxide and water molecules in the upper layers of the atmosphere. However, these small amounts were quickly consumed by the oxidation of other gases. With the appearance of autotrophic photosynthetic organisms in the ocean, the situation changed significantly. The amount of free oxygen in the atmosphere began to increase progressively, actively oxidizing many components of the biosphere. Thus, the first portions of free oxygen contributed primarily to the transition of ferrous forms of iron into oxide forms, and sulfides into sulfates.

Eventually, the amount of free oxygen in the Earth's atmosphere reached a certain mass and was balanced in such a way that the amount produced became equal to the amount absorbed. A relative constant content of free oxygen has been established in the atmosphere.

Geochemical oxygen cycle (V.A. Vronsky, G.V. Voitkevich)

Carbon dioxide, goes into the formation of living matter, and together with water vapor creates the so-called “greenhouse (greenhouse) effect.”

Carbon (carbon dioxide) - most of it in the atmosphere is in the form of CO 2 and much less in the form of CH 4. The significance of the geochemical history of carbon in the biosphere is extremely great, since it is part of all living organisms. Within living organisms, reduced forms of carbon predominate, and in the environment of the biosphere, oxidized forms predominate. Thus, the chemical exchange of the life cycle is established: CO 2 ↔ living matter.

The source of primary carbon dioxide in the biosphere is volcanic activity associated with secular degassing of the mantle and lower horizons of the earth's crust. Part of this carbon dioxide arises during the thermal decomposition of ancient limestones in various metamorphic zones. Migration of CO 2 in the biosphere occurs in two ways.

The first method is expressed in the absorption of CO 2 during photosynthesis with the formation of organic substances and subsequent burial in favorable reducing conditions in the lithosphere in the form of peat, coal, oil, and oil shale. According to the second method, carbon migration leads to the creation of a carbonate system in the hydrosphere, where CO 2 turns into H 2 CO 3, HCO 3 -1, CO 3 -2. Then, with the participation of calcium (less commonly magnesium and iron), carbonates are deposited via biogenic and abiogenic pathways. Thick layers of limestone and dolomite appear. According to A.B. Ronov, the ratio of organic carbon (Corg) to carbonate carbon (Ccarb) in the history of the biosphere was 1:4.

Along with the global carbon cycle, there are also a number of small carbon cycles. So, on land, green plants absorb CO 2 for the process of photosynthesis during the daytime, and at night they release it into the atmosphere. With the death of living organisms on the earth's surface, oxidation of organic substances occurs (with the participation of microorganisms) with the release of CO 2 into the atmosphere. In recent decades, a special place in the carbon cycle has been occupied by the massive combustion of fossil fuels and the increase in its content in the modern atmosphere.

Carbon cycle in the geographic envelope (according to F. Ramad, 1981)

Argon- the third most widespread atmospheric gas, which sharply distinguishes it from the extremely sparsely distributed other inert gases. However, argon in its geological history shares the fate of these gases, which are characterized by two features:

1. the irreversibility of their accumulation in the atmosphere;
2. close connection with the radioactive decay of certain unstable isotopes.

Inert gases are outside the cycle of most cyclic elements in the Earth's biosphere.

All inert gases can be divided into primary and radiogenic. The primary ones include those that were captured by the Earth during the period of its formation. They are extremely rare. The primary part of argon is represented mainly by the isotopes 36 Ar and 38 Ar, while atmospheric argon consists entirely of the isotope 40 Ar (99.6%), which is undoubtedly radiogenic. In potassium-containing rocks, the accumulation of radiogenic argon occurred and continues to occur due to the decay of potassium-40 through electron capture: 40 K + e → 40 Ar.

Therefore, the argon content in rocks is determined by their age and the amount of potassium. To this extent, the helium concentration in rocks is a function of their age and thorium and uranium content. Argon and helium are released into the atmosphere from the bowels of the earth during volcanic eruptions, through cracks in the earth's crust in the form of gas jets, and also during weathering of rocks. According to calculations performed by P. Dimon and J. Culp, helium and argon in the modern era accumulate in the earth's crust and enter the atmosphere in relatively small quantities. The rate of entry of these radiogenic gases is so low that during the geological history of the Earth it could not ensure their observed content in the modern atmosphere. Therefore, it remains to be assumed that most of the argon in the atmosphere came from the interior of the Earth at the earliest stages of its development, and much less was added subsequently during the process of volcanism and during the weathering of potassium-containing rocks.

Thus, over geological time, helium and argon have had different migration processes. There is very little helium in the atmosphere (about 5 * 10 -4%), and the “helium breathing” of the Earth was lighter, since it, as the lightest gas, evaporated into outer space. And “argon breathing” was heavy and argon remained within the boundaries of our planet. Most of the primordial noble gases, such as neon and xenon, were associated with primordial neon captured by the Earth during its formation, as well as with release during degassing of the mantle into the atmosphere. The entire body of data on the geochemistry of noble gases indicates that the primary atmosphere of the Earth arose at the earliest stages of its development.

The atmosphere contains water vapor And water in liquid and solid state. Water in the atmosphere is an important heat accumulator.

The lower layers of the atmosphere contain a large amount of mineral and technogenic dust and aerosols, combustion products, salts, spores and pollen, etc.

Up to an altitude of 100-120 km, due to complete mixing of air, the composition of the atmosphere is homogeneous. The ratio between nitrogen and oxygen is constant. Above, inert gases, hydrogen, etc. predominate. In the lower layers of the atmosphere there is water vapor. With distance from the earth its content decreases. Higher the ratio of gases changes, for example, at an altitude of 200-800 km, oxygen predominates over nitrogen by 10-100 times.