Caused a fierce debate in the comments on whether human civilization is the main source of greenhouse gases on the planet. Dear dims12 gave an interesting link, which says that volcanoes emit 100-500 times less carbon dioxide than modern civilization:

In response to this, dear vladimir000 brought his. As a result of him he got that emissions CO2 much less human civilization: about 600 million tons:

Something you have a strange order of numbers. The search gives the total power of all the power plants of the Earth 2 * 10 ^ 12 watts, that is, assuming that they all run on fossil fuels all year round, we get approximately 2 * 10 ^ 16 watt-hours of annual consumption, that is, 6 * 10 ^ 15 KJoules.

Again, the search yields a specific calorific value of the first tens of thousands of KJ per kilogram of fossil fuel. Let's take 10,000 for simplicity, and assume that all processed fuel flies into the pipe without residue.

Then, in order to fully cover the energy needs of mankind, it turns out that it is enough to burn 6 * 10^15 / 10^4 kilograms of carbon per year, that is, 6 * 10^8 tons. 600 megatons per year. Given that there are still nuclear, hydro and other renewable plants, I don’t see how, the final consumption will increase by 500 times.

The difference turned out to be huge - 500 times. But at the same time, I did not quite understand where this 500-fold difference came from. If you divide 29 billion tons by 600 million tons, there will be a difference of 50 times. On the other hand, this difference is probably due to not 100% efficiency power plant, and the fact that fossil fuels are consumed not only by power plants, but also for transport, home heating or cement production.

Therefore, it is possible to make this calculation more accurately. To do this, simply use the following quote: " when burning coal in the amount of one ton of standard fuel, 2.3 tons of oxygen are consumed and 2.76 tons of carbon dioxide are emitted, and when burning natural gas, 1.62 tons of carbon dioxide are emitted, and the same 2.35 tons of oxygen are consumed ".

How much fuel does humanity consume per year now? Such statistics are given in the company's reports. BP. About 13 billion tons of reference fuel. Thus, humanity emits about 26 billion tons of carbon dioxide into the atmosphere. Moreover, the same data provides detailed statistics on emissions CO2 for every year. It follows that these emissions are constantly growing:

At the same time, only half of these emissions enter the atmosphere. The other half

The formation of a large amount of N2 is due to the oxidation of the ammonia-hydrogen atmosphere by molecular O2, which began to come from the surface of the planet as a result of photosynthesis, starting from 3 billion years ago. N2 is also released into the atmosphere as a result of the denitrification of nitrates and other nitrogen-containing compounds. Nitrogen is oxidized by ozone to NO in the upper atmosphere.

Nitrogen N2 enters into reactions only under specific conditions (for example, during a lightning discharge). Oxidation of molecular nitrogen by ozone during electrical discharges is used in the industrial production of nitrogen fertilizers. It can be oxidized with low energy consumption and converted into a biologically active form by cyanobacteria (blue-green algae) and nodule bacteria that form rhizobial symbiosis with legumes, the so-called. green manure.

Oxygen

The composition of the atmosphere began to change radically with the advent of living organisms on Earth, as a result of photosynthesis, accompanied by the release of oxygen and the absorption of carbon dioxide. Initially, oxygen was spent on the oxidation of reduced compounds - ammonia, hydrocarbons, the ferrous form of iron contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to grow. Gradually, a modern atmosphere with oxidizing properties formed. Since this caused serious and abrupt changes in many processes occurring in the atmosphere, lithosphere and biosphere, this event was called the Oxygen Catastrophe.

During the Phanerozoic, the composition of the atmosphere and the oxygen content underwent changes. They correlated primarily with the rate of deposition of organic sedimentary rocks. So, during the periods of coal accumulation, the oxygen content in the atmosphere, apparently, noticeably exceeded the modern level.

Carbon dioxide

One of the most important parts of air is carbon dioxide. Near the earth's surface, carbon dioxide is found in variable amounts, averaging 0.03% by volume.

Carbon dioxide enters the atmosphere as a result of volcanic activity, decomposition and decay of organic matter, respiration of animals and plants, and fuel combustion. The main regulator of carbon dioxide content in the atmosphere is the oceans. It absorbs and releases into the atmosphere about 20% of the average content in the atmosphere.

Despite its relatively small content in the atmosphere, carbon dioxide has a great influence on the so-called "greenhouse effect". Passing short-wave solar radiation to the earth's surface, absorbing long-wave (thermal) radiation coming from the earth's surface, it contributes to an increase in air temperature in the underlying layers of the atmosphere.

In the era of industrialization, there is an increased content of carbon dioxide of anthropogenic origin.

Under the influence of human activity, the content of anthropogenic gases in the atmosphere, such as sulfur dioxide, carbon monoxide, and various nitrogen oxides, increases.

An extremely important role is played by ozone, which absorbs the part of the solar ultraviolet radiation that is unfavorable for living organisms and plants. At the earth's surface, ozone is found in small quantities: it is formed as a result of lightning discharges. Its largest amount is in the stratosphere (ozonosphere) from 10 to 50 km with a maximum in the layer at altitudes of 20-25 km. In this layer, under the action of ultraviolet radiation from the Sun, diatomic oxygen molecules partially decompose into atoms, the latter, joining the undecayed diatomic oxygen molecules, form triatomic ozone. Simultaneously with the formation of ozone, the reverse process takes place.

The concentration of ozone depends on the intensity of formation and destruction of ozone molecules. The ozone content increases from the equator to high latitudes.

An important component of the air is water vapor, which enters the atmosphere as a result of evaporation from the water surface, land, during volcanic eruptions. The lower layers of the atmosphere contain from 0.1 to 4% of water vapor. With height, its content sharply decreases.

Water vapor is actively involved in many thermodynamic processes associated with the formation of clouds and fogs.

Aerosols are present in the atmosphere - these are solid and liquid particles that are suspended in the air. Some of them, being nuclei of condensation, are involved in the formation of clouds and fogs.

Natural aerosols include water droplets and ice crystals formed during the condensation of water vapor; dust, soot arising from forest fires, soil, space, volcanic dust, salts of sea water. Also enters the atmosphere a large number of aerosols of artificial origin - emissions from industrial enterprises, vehicles, etc.

The greatest amount of aerosols is contained in the lower layers of the atmosphere.

4. The structure of the atmosphere.

The mass of the atmosphere is 5.3 * 105 tons. In a layer up to 5.5 km

contains 50%, up to 25 km - 95% and up to 30 km - 99% of the total mass of the atmosphere. The thirty-kilometer layer of the atmosphere is 1/200 or 0.05 of the radius of the Earth. On a globe 40 cm in diameter, this 30 km layer is about 1 mm thick; The atmosphere is a thin film that covers the Earth's surface.

lower boundary of the atmosphere is the earth's surface, called in meteorology the underlying surface. The atmosphere does not have a clearly defined upper boundary. It smoothly passes into interplanetary space.

Per upper limit of the atmosphere conditionally take a height of 1500-2000 km, above which is the earth's corona.

Pressure and density decrease with height: at a pressure near the ground of 1013 hPa, the density is 1.27 * 103 g / m3, and at an altitude of 750 km the density is 10-10 g / m3.

Distribution physical properties in the atmosphere it has a layered character, since their change in height occurs many times more intense than in the horizontal direction. Thus, vertical temperature gradients are several hundred times larger than horizontal gradients.

The division of the atmosphere into layers is done according to various properties air: by temperature, humidity, ozone content, electrical conductivity, etc. The difference between the layers of the atmosphere is most clearly manifested in the nature of the distribution of air temperature with height. On this basis, five main layers are distinguished.

Very large. Carbon dioxide takes part in the formation of all living matter on the planet and, together with water and methane molecules, creates the so-called "greenhouse (greenhouse) effect."

Carbon dioxide value ( CO 2 , dioxide or carbon dioxide) in the life of the biosphere consists primarily in maintaining the process of photosynthesis, which is carried out by plants.

Being greenhouse gas, carbon dioxide in the air affects the heat exchange of the planet with the surrounding space, effectively blocking the reradiated heat at a number of frequencies, and thus participates in the formation.

AT recent times there is an increase in the concentration of carbon dioxide in the air, which leads to.

Carbon (C) in the atmosphere is found mainly in the form of carbon dioxide (CO 2) and in a small amount in the form of methane (CH 4), carbon monoxide and other hydrocarbons.

For atmospheric gases, the concept of "gas lifetime" is used. This is the time during which the gas is completely renewed, i.e. the time it takes for as much gas to enter the atmosphere as it contains. So, for carbon dioxide this time is 3-5 years, for methane - 10-14 years. CO oxidizes to CO 2 within a few months.

In the biosphere, the importance of carbon is very high, since it is part of all living organisms. Within living beings, carbon is contained in a reduced form, and outside the biosphere - in an oxidized form. Thus, the chemical exchange of the life cycle is formed: CO 2 ↔ living matter.

Sources of carbon in the atmosphere.

The source of primary carbon dioxide is, during the eruption of which a huge amount of gases is released into the atmosphere. Part of this carbon dioxide arises from the thermal decomposition of ancient limestones in various metamorphic zones.

Carbon also enters the atmosphere in the form of methane as a result of anaerobic decomposition of organic residues. Methane under the influence of oxygen is quickly oxidized to carbon dioxide. The main suppliers of methane to the atmosphere are tropical forests and.

In turn, atmospheric carbon dioxide is a source of carbon for other geospheres -, the biosphere and.

Migration of CO 2 in the biosphere.

Migration of CO 2 proceeds in two ways:

In the first method, CO 2 is absorbed from the atmosphere during photosynthesis and participates in the formation of organic substances with subsequent burial in the form of minerals: peat, oil, oil shale.

In the second method, carbon is involved in the creation of carbonates in the hydrosphere. CO 2 goes into H 2 CO 3, HCO 3 -1, CO 3 -2. Then, with the participation of calcium (less often magnesium and iron), the precipitation of carbonates occurs in a biogenic and abiogenic way. Thick strata of limestones and dolomites 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.

How is the geochemical cycle of carbon carried out in nature and how carbon dioxide is returned back to the atmosphere

Carbon dioxide (CO2).

Carbon dioxide is perhaps the most important of all the greenhouse gases released into the atmosphere by humans, firstly because it causes a strong greenhouse effect and, secondly, because so much of this gas is produced by humans.

Carbon dioxide is a very "natural" component of the atmosphere - so natural that we have only recently begun to think about anthropogenic carbon dioxide as a pollutant. Carbon dioxide can be a useful thing. However, the key question is at what point does CO2 become too much? Or, in other words, in what quantities does it begin to have a harmful effect on the environment?

What seems natural from the point of view of man today may differ significantly from what was natural for the Earth in the process of its evolutionary development. The history of mankind is only a very thin slice (no more than a few million years) on a geological layer of more than 4.6 billion years.

Some environmentalists fear that carbon dioxide will lead to catastrophic changes in the climate, such as those described in Bill McKibben's book Nature's End.

Most likely, carbon dioxide dominated the Earth's early atmosphere. Atmospheric CO2 is only about 0.03 percent today, and the most pessimistic predictions are for it to rise to 0.09 percent by 2100. Approximately 4.5 billion years ago, some scientists believe that CO2 made up 80 percent of the composition of the Earth's atmosphere, slowly dropping initially to 30-20 percent over the next 2.5 billion years. Free oxygen was virtually non-existent in the early atmosphere and was poisonous to the anaerobic life forms that existed at that time.

The existence of man, as we know today, in conditions of excess carbon dioxide in the atmosphere, was simply impossible. Fortunately for humans and animals, most of the CO2 was removed from the atmosphere late in Earth's history, when sea dwellers, early forms of algae, developed the ability to photosynthesize. During photosynthesis, plants use the sun's energy to convert carbon dioxide and water into sugar and oxygen. In the end, algae and other, more advanced life forms that evolved (plankton, plants, and trees) died, sequestering most of the carbon in various carbon minerals (oil shale, coal, and oil) in the earth's crust. What's left in the atmosphere is the oxygen we breathe now.

Carbon dioxide enters the atmosphere from various sources - most of which are natural. But the amount of CO2 usually stays about the same level, because there are mechanisms that remove carbon dioxide from the atmosphere (Figure 5 gives a simplified diagram of the circulation of CO2 in the atmosphere).

One of the main natural mechanisms of CO2 circulation is the exchange of gases between the atmosphere and the surface of the oceans. This exchange is a very subtle, well-balanced feedback process. The amount of carbon dioxide involved in it is truly enormous. Scientists measure these quantities in giga tons (Ggt - billions of metric tons) of carbon for convenience.

Carbon dioxide readily dissolves in water (the process that produces carbonated water). It is also easily released from the water (in carbonated water, we see this as a fizz). Atmospheric carbon dioxide is continuously dissolved in water at the surface of the oceans and released back into the atmosphere. This phenomenon is almost entirely explained by physical and chemical processes. The surface of the world's oceans annually releases 90 Ggt of carbon, and absorbs 92 Ggt of carbon. When scientists compare these two processes, it turns out that the surface of the world's oceans, in fact, is a carbon dioxide sink, that is, it absorbs more CO2 than it releases back into the atmosphere.

The magnitude of carbon dioxide fluxes in the atmosphere/ocean cycle remains the most an important factor, because minor changes in the existing balance can have unpredictable consequences for other natural processes.

Biological processes play an equally important role in the circulation of carbon dioxide in the atmosphere. CO2 is essential for photosynthesis. Plants "breathe" carbon dioxide, absorbing about 102 Ggt of carbon annually. However, plants, animals and other organisms also emit CO2. One of the reasons for the formation of carbon dioxide is explained by the metabolic process - respiration. When breathing, living organisms burn the oxygen they breathe. Humans and other land animals, for example, inhale oxygen to sustain life and exhale carbon dioxide back into the atmosphere as waste. According to calculations, all living organisms on Earth annually exhale about 50 Ggt of carbon.

When plants and animals die, the organic carbon compounds found in them are incorporated into the soil or silt in swamps. Nature composts these products of withered life like a gardener, breaking them down into their constituent parts through various chemical transformations and the work of microorganisms. According to scientists, during the decay, about 50 Ggt of carbon gets back into the atmosphere.

Thus, 102 Ggt of carbon taken from the atmosphere annually is almost one hundred percent balanced by the 102 Gg tons of carbon that enters the atmosphere annually through the respiration and decay of animals and plants. It is necessary to be fully aware of the magnitude of carbon fluxes in nature, since slight deviations in the existing balance can have far-reaching consequences.

Compared to the atmosphere-ocean cycle and the biological cycle, the amount of carbon dioxide released into the atmosphere as a result of human activities, at first glance, seems negligible. When burning coal, oil and natural gas, a person releases approximately 5.7 Ggt of carbon into the atmosphere (according to IPCC). When cutting down and burning forests, people add another 2 Gg tons. It should be noted that there are different estimates of the amount of carbon released into the atmosphere as a result of deforestation.

These quantities undoubtedly play a role because the natural carbon cycles (atmosphere/ocean and biological cycle) have long been in a well-adjusted equilibrium. At least, the balance was maintained in the time period in which the origin and development of mankind took place. Human industrial and agricultural activities seem to have significantly skewed the carbon balance.

Various scientific studies have shown an increase in carbon dioxide concentrations in the atmosphere over the past few centuries. During this time, the world's population grew exponentially, industry began to use the steam engine, internal combustion vehicles spread throughout the planet, and migrant farmers cleared vast areas of America, Australia and Asia from vegetation.

During the same time, atmospheric concentrations of carbon dioxide increased from 280 parts per million (ppmv) pre-industrial (1750) to about 353 ppmv, about 25 percent. This amount could be enough to cause significant changes if the climate is indeed sensitive to greenhouse gases to the extent that scientists suggest. Measurements at the Manua Loa Observatory in Hawaii, far removed from sources of industrial pollution, show a steady increase in CO2 concentrations between 1958 and 1990 (Figure 6). In the past two years, however, no increase in carbon dioxide concentrations has been observed.

The close relationship between carbon dioxide concentrations and estimated average global temperatures is amazing (Figure 7)! However, whether this correlation is random is still a mystery. It is easy to be tempted to attribute fluctuations in temperature to fluctuations in CO2 concentrations. But the relationship can also be reversed - a change in temperature can cause a change in carbon dioxide concentrations.

The composition and structure of the atmosphere.

The atmosphere is the gaseous envelope of the Earth. The vertical extent of the atmosphere is more than three earth radii (the average radius is 6371 km) and the mass is 5.157 x 10 15 tons, which is approximately one millionth of the mass of the Earth.

The division of the atmosphere into layers in the vertical direction is based on the following:

Compound atmospheric air,

Physical and chemical processes;

Altitude temperature distribution;

Interaction of the atmosphere with the underlying surface.

The atmosphere of our planet is a mechanical mixture of various gases, including water vapor, as well as a certain amount of aerosols. The composition of dry air in the lower 100 km remains almost constant. Clean and dry air, in which there is no water vapor, dust and other impurities, is a mixture of gases, mainly nitrogen (78% of air volume) and oxygen (21%). A little less than one percent is argon, and in very small quantities there are many other gases - xenon, krypton, carbon dioxide, hydrogen, helium, etc. (Table 1.1).

Nitrogen, oxygen and other components of atmospheric air are always in the atmosphere in a gaseous state, since the critical temperatures, that is, the temperatures at which they can be in a liquid state, are much lower than the temperatures observed at the Earth's surface. The exception is carbon dioxide. However, for the transition to a liquid state, in addition to temperature, it is also necessary to reach a state of saturation. There is not much carbon dioxide in the atmosphere (0.03%) and it is in the form of individual molecules, evenly distributed among the molecules of other atmospheric gases. Over the past 60-70 years, its content has increased by 10-12%, under the influence of human activities.

More than others, the content of water vapor is subject to change, the concentration of which at the Earth's surface at high temperature can reach 4%. With an increase in altitude and a decrease in temperature, the content of water vapor decreases sharply (at a height of 1.5-2.0 km - by half and 10-15 times from the equator to the pole).

The mass of solid impurities over the past 70 years in the atmosphere of the northern hemisphere has increased by about 1.5 times.

The constancy of the gas composition of the air is ensured by intensive mixing of the lower layer of air.

Gas composition of the lower layers of dry air (without water vapor)

The role and importance of the main gases of atmospheric air

OXYGEN (O) vital for almost all the inhabitants of the planet. It is an active gas. It participates in chemical reactions with other atmospheric gases. Oxygen actively absorbs radiant energy, especially very short wavelengths less than 2.4 μm. Under the influence of solar ultraviolet radiation (X< 03 µm), the oxygen molecule breaks up into atoms. Atomic oxygen, combining with an oxygen molecule, forms a new substance - triatomic oxygen or ozone(Oz). Ozone is mostly found at high altitudes. There his role for the planet is exceptionally beneficial. At the surface of the Earth, ozone is formed during lightning discharges.

Unlike all other gases in the atmosphere, which have neither taste nor smell, ozone has a characteristic smell. Translated from Greek, the word "ozone" means "sharp smelling". After a thunderstorm, this smell is pleasant, it is perceived as the smell of freshness. In large quantities, ozone is a poisonous substance. In cities with a large number of cars, and therefore large emissions of automobile gases, ozone is formed under the action of sunlight in cloudless or slightly cloudy weather. The city is shrouded in a yellow-blue cloud, visibility is deteriorating. This is photochemical smog.

NITROGEN (N2) is a neutral gas, it does not react with other gases of the atmosphere, does not participate in the absorption of radiant energy.

Up to altitudes of 500 km, the atmosphere mainly consists of oxygen and nitrogen. At the same time, if nitrogen prevails in the lower layer of the atmosphere, then at high altitudes there is more oxygen than nitrogen.

ARGON (Ag) - a neutral gas, does not enter into a reaction, does not participate in the absorption and emission of radiant energy. Similarly - xenon, krypton and many other gases. Argon is a heavy substance, it is very scarce in the high layers of the atmosphere.

CARBON DIOXIDE (CO2) in the atmosphere is on average 0.03%. This gas is very necessary for plants and is actively absorbed by them. The actual amount in the air may vary somewhat. In industrial areas, its amount can increase up to 0.05%. In the countryside, above the forests, there are fewer fields. Over Antarctica, approximately 0.02% of carbon dioxide, i.e., almost Ouse less than the average amount in the atmosphere. The same amount and even less over the sea - 0.01 - 0.02%, since carbon dioxide is intensively absorbed by water.

In the layer of air that is directly adjacent to the earth's surface, the amount of carbon dioxide also experiences daily fluctuations.

More at night, less during the day. This is explained by the fact that during the daytime, carbon dioxide is absorbed by plants, but not at night. Plants of the planet during the year take about 550 billion tons of oxygen from the atmosphere and return about 400 billion tons of oxygen to it.

Carbon dioxide is completely transparent to short-wavelength solar rays, but intensely absorbs the thermal infrared radiation of the Earth. Related to this is the problem of the greenhouse effect, about which discussions periodically flare up on the pages of the scientific press, and mainly in the mass media.

HELIUM (He) is a very light gas. It enters the atmosphere from earth's crust from the radioactive decay of thorium and uranium. Helium escapes into outer space. The rate of decrease of helium corresponds to the rate of its entry from the bowels of the Earth. From an altitude of 600 km to 16,000 km, our atmosphere consists mainly of helium. This is the "helium corona of the Earth" in the words of Vernadsky. Helium does not react with other atmospheric gases and does not participate in radiant heat transfer.

HYDROGEN (Hg) is an even lighter gas. There is very little of it near the Earth's surface. It rises to the upper atmosphere. In the thermosphere and exosphere, atomic hydrogen becomes the dominant component. Hydrogen is the topmost, most distant shell of our planet. Above 16,000 km to the upper boundary of the atmosphere, that is, up to altitudes of 30-40 thousand km, hydrogen predominates. Thus, the chemical composition of our atmosphere with height approaches the chemical composition of the Universe, in which hydrogen and helium are the most abundant elements. In the outermost, extremely rarefied part of the upper atmosphere, hydrogen and helium escape from the atmosphere. Their individual atoms have sufficiently high speeds for this.