In the last decade, the phrase "greenhouse effect" has practically never left the television screens or from the pages of newspapers. Learning programs in several disciplines at once, they provide for its thorough study, and its negative significance for the climate of our planet is almost always indicated. However, this phenomenon is actually much more multifaceted than it is presented to the layman.
Without the greenhouse effect, life on our planet would be in question
You can start with the fact that the greenhouse effect on our planet has existed throughout its history. Such a phenomenon is simply inevitable for those celestial bodies that, like the Earth, have a stable atmosphere. Without it, for example, the World Ocean would have frozen long ago, and the higher forms of life would not have appeared at all. Scientists have long scientifically proved that if there were no carbon dioxide in our atmosphere, the presence of which is a necessary factor in the process of the emergence of the greenhouse effect, then the temperature on the planet would fluctuate within -20 0 C, so there would be no talk of the emergence of life at all.
Causes and essence of the greenhouse effect
Answering the question: "What is the greenhouse effect?", First of all, it should be noted that this physical phenomenon got its name by analogy with the processes that occur in the gardeners' greenhouse. Inside it, regardless of the season, it is always a few degrees warmer than in the surrounding space. The thing is that plants absorb visible sunlight, which pass absolutely freely through glass, and through polyethylene, and in general through almost any obstacle. After that, the plants themselves also begin to radiate energy, but already in the infrared range, the rays of which can no longer freely overcome the same glass, so a greenhouse effect occurs. The reasons for this phenomenon, therefore, lie precisely in the imbalance between the spectrum of visible sunlight and those radiations that give off external environment plants and other items.
The physical basis of the greenhouse effect
As for our planet as a whole, the greenhouse effect here arises due to the presence of a stable atmosphere. To maintain its temperature balance, the Earth must give off as much energy as it receives from the Sun. However, the presence in the atmosphere carbon dioxide and water, which absorb infrared rays, thus acting as glass in a greenhouse, causes the formation of so-called greenhouse gases, some of which returns back to the Earth. These gases create a "quilt effect", raising the temperature near the surface of the planet.
Greenhouse effect on Venus
From the foregoing, we can conclude that the greenhouse effect is characteristic not only for the Earth, but also for all planets and other celestial bodies with a stable atmosphere. Indeed, studies conducted by scientists have shown that, for example, on the surface of Venus, this phenomenon is much more pronounced, which is primarily due to the fact that its air envelope is almost one hundred percent carbon dioxide.
The average surface temperature of the Earth (or another planet) rises due to the presence of an atmosphere.
Gardeners are well aware of this. physical phenomenon. Inside the greenhouse is always warmer than outside, and this helps to grow plants, especially in the cold season. You may experience a similar effect when you are in a car. The reason for this is that the Sun, with a surface temperature of about 5000 ° C, emits mainly visible light - the part of the electromagnetic spectrum that our eyes are sensitive to. Since the atmosphere is largely transparent to visible light, solar radiation easily penetrates to the surface of the Earth. Glass is also transparent to visible light, so Sun rays pass inside the greenhouse, and their energy is absorbed by plants and all objects inside. Further, according to the Stefan-Boltzmann law, each object radiates energy in some part of the electromagnetic spectrum. Objects with a temperature of about 15°C - the average temperature at the Earth's surface - radiate energy in the infrared range. Thus, the objects in the greenhouse emit infrared radiation. However, infrared radiation cannot easily pass through the glass, so the temperature inside the greenhouse rises.
A planet with a stable atmosphere, like Earth, experiences much the same effect—on a global scale. To maintain a constant temperature, the Earth itself needs to radiate as much energy as it absorbs from the visible light radiated towards us by the Sun. The atmosphere serves as a kind of glass in a greenhouse - it is not as transparent to infrared radiation as it is to sunlight. molecules various substances in the atmosphere (the most important of which are carbon dioxide and water) absorb infrared radiation, acting as greenhouse gases. Thus, infrared photons emitted by the earth's surface do not always go straight into space. Some of them are absorbed by greenhouse gas molecules in the atmosphere. When these molecules re-radiate the energy they have absorbed, they can radiate it both towards space and inward, back to the surface of the Earth. The presence of such gases in the atmosphere creates the effect of covering the Earth with a blanket. They cannot stop heat from escaping to the outside, but they allow heat to remain near the surface for a longer time, so the Earth's surface is much warmer than it would be in the absence of gases. Without the atmosphere, the average surface temperature would be -20°C, well below the freezing point of water.
It is important to understand that the greenhouse effect has always existed on Earth. Without the greenhouse effect caused by the presence of carbon dioxide in the atmosphere, the oceans would have frozen over long ago, and higher forms of life would not have appeared. Currently, the scientific debate about the greenhouse effect is on the issue global warming : Are we humans disturbing the planet's energy balance too much by burning fossil fuels and other economic activity while adding too much carbon dioxide to the atmosphere? Today, scientists agree that we are responsible for increasing the natural greenhouse effect by several degrees.
Greenhouse effect takes place not only on Earth. In fact, the strongest greenhouse effect we know of is on the neighboring planet, Venus. The atmosphere of Venus is almost entirely composed of carbon dioxide, and as a result, the surface of the planet is heated to 475 ° C. Climatologists believe that we have avoided such a fate thanks to the presence of oceans on Earth. The oceans absorb atmospheric carbon and it accumulates in rocks such as limestone - through this, carbon dioxide is removed from the atmosphere. There are no oceans on Venus, and all the carbon dioxide emitted into the atmosphere by volcanoes remains there. As a result, we observe on Venus ungovernable Greenhouse effect.
Earth as a result of the impact of human activities. Of particular concern is the increase in the concentration of greenhouse gases in , which leads to heating of the Earth's surface and lower atmosphere and, perhaps, is one of the main reasons for the climate warming observed in recent decades.
The most significant natural greenhouse gas is H20 water vapor. It absorbs and emits long-wave infrared radiation in the wavelength range of 4.5 - 80 microns. The influence of water vapor on the greenhouse effect is decisive and is created mainly by the absorption band 5 - 7.5 μm. Nevertheless, part of the radiation from the Earth's surface in the spectral regions of 3 - 5 µm and 8 - 12 µm, called transparency windows, escapes through the atmosphere into the world space. The greenhouse effect of water vapor is enhanced by the absorption bands of carbon dioxide, which enters the atmosphere as a result of volcanic activity, the natural cycle of carbon in nature, decay organic matter in the soil when heated, as well as human activity, mainly due to the burning of fossil fuels (coal, oil, gas) and deforestation.
In addition to carbon dioxide, the content of greenhouse gases such as methane, nitrous oxide and tropospheric ozone is increasing in the atmosphere. Methane enters the atmosphere from swamps and deep cracks in earth's crust. The increase in its concentration is facilitated by the development of agricultural production (especially the expansion of abundantly irrigated rice fields), an increase in the number of livestock, biomass burning and mining natural gas. The concentration of nitrous oxide is increased by the use nitrogen fertilizers, aircraft emissions, and oxidation processes. Ozone in the troposphere is increasing as a result of chemical reactions sunlight between hydrocarbons and nitrogen oxides from the combustion of fossil fuels These gases are increasing faster than carbon dioxide concentrations and may increase their relative contribution to the atmospheric greenhouse effect in the future. The growth of the atmosphere is also facilitated by an increase in the concentration of a highly absorbing aerosol of industrial origin (soot) with a particle radius of 0.001 - 0.05 microns. An increase in greenhouse gases and aerosols could significantly increase global temperatures and cause other climate changes, the environmental and social consequences of which are still difficult to predict.
The greenhouse effect is a rise in temperature on the surface of the planet as a result of thermal energy that appears in the atmosphere due to the heating of gases. The main gases that lead to the greenhouse effect on Earth are water vapor and carbon dioxide.
The phenomenon of the greenhouse effect makes it possible to maintain a temperature on the Earth's surface at which the emergence and development of life is possible. If there were no greenhouse effect, the average surface temperature the globe would be much lower than it is now. However, as the concentration of greenhouse gases rises, the atmosphere's impermeability to infrared rays increases, which leads to an increase in the temperature of the Earth.
In 2007, the Intergovernmental Panel on Climate Change (IPCC) - the most authoritative international body that brings together thousands of scientists from 130 countries - presented its Fourth Assessment Report, which contained generalized conclusions about past and current climate change, their impact on nature and humans , as well as possible measures to counteract such changes.
According to published data, from 1906 to 2005, the average temperature of the Earth rose by 0.74 degrees. In the next 20 years, temperature growth, according to experts, will average 0.2 degrees per decade, and end of XXI century, the temperature of the Earth can rise from 1.8 to 4.6 degrees (such a difference in the data is the result of superimposing a whole range of future climate models that take into account various scenarios for the development of the world economy and society).
According to scientists, with a 90 percent probability, observed climate changes are associated with human activities - the burning of carbon fossil fuels (i.e. oil, gas, coal, etc.), industrial processes, as well as the deforestation - natural sinks of carbon dioxide from the atmosphere .
Possible impacts of climate change:
1. Change in the frequency and intensity of precipitation.
In general, the climate on the planet will become more humid. But the amount of precipitation will not spread evenly across the Earth. In regions that already receive enough rainfall today, their fallout will become more intense. And in regions with insufficient moisture, dry periods will become more frequent.
2. Sea level rise.
During the twentieth century average level sea level rose by 0.1-0.2 m. According to scientists, in the 21st century the sea level rise will be up to 1 m. In this case, coastal areas and small islands will be the most vulnerable. States such as the Netherlands, Great Britain, as well as the small island states of Oceania and the Caribbean will be the first to fall under the risk of flooding. In addition, high tides will become more frequent, erosion will increase coastline.
3. Threat to ecosystems and biodiversity.
There are forecasts for the extinction of up to 30-40% of plant and animal species, as their habitat will change faster than they can adapt to these changes.
When the temperature rises by 1 degree, a change is predicted species composition the woods. Forests are a natural carbon store (80% of all carbon in terrestrial vegetation and about 40% of carbon in soil). The transition from one type of forest to another will be accompanied by the allocation a large number carbon.
4. Melting glaciers.
The current glaciation of the Earth can be considered one of the most sensitive indicators of ongoing global change. Satellite data show that since the 1960s there has been a decrease in the area of snow cover by about 10%. Since the 1950s in the Northern Hemisphere, the area sea ice decreased by almost 10-15%, and the thickness decreased by 40%. According to the forecasts of experts from the Arctic and Antarctic Research Institute (St. Petersburg), in 30 years the Arctic Ocean will completely open from under the ice during the warm period of the year.
According to scientists, the thickness of the Himalayan ice is melting at a rate of 10-15 m per year. At the current rate of these processes, two-thirds of the glaciers will disappear by 2060, and by 2100 all glaciers will have completely melted.
Accelerated glacier melt poses a range of immediate threats human development. For densely populated mountainous and foothill areas, avalanches, floods or, conversely, a decrease in the full flow of rivers, and as a result, a reduction in reserves, are of particular danger. fresh water.
5. Agriculture.
Impact of warming on productivity Agriculture ambiguously. In some temperate areas, yields may increase with a small increase in temperature, but decrease with large changes in temperature. In tropical and subtropical regions, overall yields are projected to decrease.
The worst hit could be inflicted on the poorest countries least prepared to adapt to climate change. According to the IPCC, by 2080 the number of people facing the threat of hunger could increase by 600 million people, doubling more number people who today live in poverty in sub-Saharan Africa.
6. Water consumption and water supply.
One of the consequences of climate change could be a lack of drinking water. In dry regions ( central Asia, Mediterranean, South Africa, Australia, etc.) the situation will be further aggravated due to the reduction in precipitation.
Due to the melting of glaciers, the flow of the largest waterways in Asia - the Brahmaputra, the Ganges, the Yellow River, the Indus, the Mekong, Salween and the Yangtze - will significantly decrease. The lack of fresh water will affect not only human health and agricultural development, but will also increase the risk of political divisions and conflicts over access to water resources.
7. Human health.
Climate change, according to scientists, will lead to increased health risks for people, especially for the poorer segments of the population. Thus, a reduction in food production will inevitably lead to malnutrition and hunger. abnormal high temperatures can lead to exacerbation of cardiovascular, respiratory and other diseases.
An increase in temperature may lead to a change in geographic distribution various kinds that are carriers of diseases. As the temperature rises, the ranges of heat-loving animals and insects (for example, encephalitis mites and malarial mosquitoes) will spread further north, while the people inhabiting these areas will not have immunity to new diseases.
According to environmentalists, humanity is unlikely to be able to prevent completely predictable climate change. However, in human strength mitigate climate change, contain the rate of temperature increase in order to avoid dangerous and irreversible consequences in the future. First of all, due to:
1. Restrictions and reductions in the consumption of fossil carbon fuels (coal, oil, gas);
2. Improving the efficiency of energy consumption;
3. Implementation of energy saving measures;
4. Greater use of non-carbon and renewable energy sources;
5. Development of new environmentally friendly and low-carbon technologies;
6. Through prevention forest fires and reforestation, as forests are natural sinks of carbon dioxide from the atmosphere.
The greenhouse effect takes place not only on Earth. A strong greenhouse effect is on the neighboring planet, Venus. The atmosphere of Venus is almost entirely composed of carbon dioxide, and as a result, the surface of the planet is heated to 475 degrees. Climatologists believe that the Earth avoided such a fate due to the presence of oceans on it. The oceans absorb atmospheric carbon and it accumulates in rocks such as limestone - through this carbon dioxide is removed from the atmosphere. There are no oceans on Venus, and all the carbon dioxide emitted into the atmosphere by volcanoes remains there. As a result, an uncontrollable greenhouse effect is observed on the planet.
The material was prepared on the basis of information from RIA Novosti and open sources
The mechanism of the greenhouse effect is as follows. The sun's rays, reaching the Earth, are absorbed by the soil surface, vegetation, water surface, etc. Heated surfaces give off thermal energy back into the atmosphere, but in the form of long-wave radiation.
Atmospheric gases (oxygen, nitrogen, argon) do not absorb thermal radiation with earth's surface, but scatter it. However, as a result of burning fossil fuels and other production processes accumulate in the atmosphere: carbon dioxide, carbon monoxide, various hydrocarbons (methane, ethane, propane, etc.), which do not scatter, but absorb thermal radiation coming from the Earth's surface. The screen that arises in this way leads to the appearance of the greenhouse effect - global warming.
In addition to the greenhouse effect, the presence of these gases causes the formation of the so-called photochemical smog. At the same time, as a result of photochemical reactions, hydrocarbons form very toxic products - aldehydes and ketones.
Global warming is one of the most significant consequences of anthropogenic pollution of the biosphere. It manifests itself both in climate change and in biota: the production process in ecosystems, the shift in the boundaries of plant formations, and changes in crop yields. Especially strong changes can affect high and middle latitudes. According to forecasts, it is here that the temperature of the atmosphere will increase most noticeably. The nature of these regions is especially susceptible to various impacts and is extremely slowly restored.
As a result of warming, the taiga zone will shift to the north by about 100-200 km. The rise in the ocean level due to warming (melting of ice and glaciers) can be up to 0.2 m, which will lead to the flooding of the mouths of large, especially Siberian, rivers.
At the regular conference of the countries-participants of the Convention on Prevention of Climate Change, held in Rome in 1996, the need for coordinated international action to solve this problem was once again confirmed. In accordance with the Convention, industrialized countries and countries with economies in transition have assumed obligations to stabilize the production of greenhouse gases. The countries of the European Union have included in their national programs provisions to reduce carbon emissions by 20% by 2005.
In 1997, the Kyoto (Japan) agreement was signed, under which developed countries pledged to stabilize greenhouse gas emissions at the 1990 level by 2000.
However, greenhouse gas emissions have even increased since then. This was facilitated by the US withdrawal from the 2001 Kyoto Agreement. Thus, the implementation of this agreement was threatened with disruption, since the quota necessary for the entry into force of this agreement was violated.
In Russia, due to the general decline in production, greenhouse gas emissions in 2000 amounted to 80% of the 1990 level. Therefore, in 2004 Russia ratified the Kyoto agreement, giving it a legal status. Now (2012) this agreement is in force, other states (for example, Australia) join it, but the decisions of the Kyoto Agreement remain unfulfilled. However, the struggle to implement the Kyoto agreement continues.
One of the most famous fighters against global warming is the former Vice President of the United States. A. Gore. After losing the 2000 presidential election, he dedicates himself to combating global warming. "Save the world before it's too late!" is its slogan. Armed with a set of slides, he traveled the world explaining the science and politics of global warming, the potential for serious consequences in the near future, if not limited by the rise in human-caused carbon dioxide emissions.
A. Gore wrote a widely known book “Inconvenient truth. Global warming, how to stop a planetary catastrophe. In it, he confidently and rightly writes: “Sometimes it seems that our climate crisis is proceeding slowly, but in fact it is happening very quickly, becoming a truly planetary danger. And in order to defeat the threat, we must first recognize the fact of its existence. Why don't our leaders seem to hear such loud warnings of danger? They resist the truth, because at the moment of recognition they will face their moral duty - to act. Is it just much more convenient to ignore the danger warning? Perhaps, but an inconvenient truth does not disappear just because it is not seen.
In 2006, he was awarded the American Literary Prize for the book. Based on the book was created documentary « The Inconvenient Truth" with A. Gore in the title role. The film in 2007 received an Oscar and was included in the rubric "Everyone Should Know This". In the same year, A. Gore (together with the IPCC expert group) was awarded Nobel Prize world for their work in environmental protection and research on climate change.
Currently, A. Gore is also actively continuing the fight against global warming, being a freelance consultant for the Intergovernmental Panel on Climate Change (IPCC), established by the World Meteorological Organization (WMO) and the United Nations Program for environment(UNEP).
Global warming and greenhouse effect
Back in 1827, the French physicist J. Fourier suggested that the Earth's atmosphere performs the function of glass in a greenhouse: air passes solar heat, but prevents it from evaporating back into space. And he was right. This effect is achieved due to some atmospheric gases, such as water vapor and carbon dioxide. They transmit visible and "near" infrared light emitted by the Sun, but absorb "far" infrared radiation, which is formed when the earth's surface is heated by the sun's rays and has a lower frequency (Fig. 12).
In 1909, the Swedish chemist S. Arrhenius for the first time emphasized the enormous role of carbon dioxide as a temperature regulator of the near-surface air layers. Carbon dioxide freely transmits the sun's rays to the earth's surface, but absorbs most of the thermal radiation of the earth. This is a kind of colossal screen that prevents the cooling of our planet.
The temperature of the Earth's surface is steadily increasing, having increased over the XX century. by 0.6 °C. In 1969 it was 13.99°C, in 2000 it was 14.43°C. Thus, the average temperature of the Earth at present is about 15 °C. At a given temperature, the surface of the planet and the atmosphere are in thermal equilibrium. Heated by the energy of the Sun and the infrared radiation of the atmosphere, the surface of the Earth returns an average equivalent amount of energy to the atmosphere. This is the energy of evaporation, convection, heat conduction and infrared radiation.
Rice. 12. Schematic representation of the greenhouse effect due to the presence of carbon dioxide in the atmosphere
AT recent times human activity introduces an imbalance in the ratio of absorbed and released energy. Before human intervention in global processes on the planet, changes occurring on its surface and in the atmosphere were associated with the content of gases in nature, which light hand scientists were called "greenhouse". These gases include carbon dioxide, methane, nitric oxide and water vapor (Fig. 13). Now anthropogenic chlorofluorocarbons (CFCs) have been added to them. Without the gas "blanket" enveloping the Earth, the temperature on its surface would be 30-40 degrees lower. The existence of living organisms in this case would be very problematic.
Greenhouse gases temporarily trap heat in our atmosphere, creating the so-called greenhouse effect. As a result of man-made human activities, some greenhouse gases increase their share in the overall balance of the atmosphere. This applies primarily to carbon dioxide, the content of which has been steadily increasing from decade to decade. Carbon dioxide creates 50% of the greenhouse effect, CFCs account for 15-20%, and methane accounts for 18%.
Rice. 13. The proportion of anthropogenic gases in the atmosphere with the greenhouse effect of nitrogen 6%
In the first half of the XX century. the content of carbon dioxide in the atmosphere was estimated at 0.03%. In 1956, within the framework of the first International Geophysical Year, scientists conducted special studies. The given figure was adjusted and amounted to 0.028%. In 1985, measurements were taken again, and it turned out that the amount of carbon dioxide in the atmosphere had increased to 0.034%. Thus, an increase in the content of carbon dioxide in the atmosphere is a proven fact.
Over the past 200 years, as a result of anthropogenic activities, the content of carbon monoxide in the atmosphere has increased by 25%. This is due, on the one hand, to the intensive burning of fossil fuels: gas, oil, shale, coal, etc., and on the other hand, to the annual decrease in forest areas, which are the main sinks of carbon dioxide. In addition, the development of such agricultural sectors as rice growing and animal husbandry, as well as the growth of urban landfill areas, lead to an increase in the emission of methane, nitrogen oxide and some other gases.
Methane is the second most important greenhouse gas. Its content in the atmosphere increases by 1% annually. The most significant suppliers of methane are landfills, cattle, and rice fields. Gas reserves in the landfills of large cities can be considered as small gas fields. As for the rice fields, as it turned out, despite big exit methane, relatively little of it enters the atmosphere, since most of it is broken down by bacteria associated with the rice root system. Thus, the impact of rice agricultural ecosystems on the release of methane into the atmosphere is generally moderate.
Today there is no doubt that the trend towards the use of predominantly fossil fuels inevitably leads to global catastrophic climate change. At the current rate of use of coal and oil in the next 50 years, an increase in the average annual temperature on the planet is predicted in the range from 1.5 ° C (near the equator) to 5 ° C (in high latitudes).
An increase in temperature as a result of the greenhouse effect threatens unprecedented environmental, economic and social consequences. The water level in the oceans can rise by 1-2 m due to sea water and melting polar ice. (Due to the greenhouse effect, the level of the World Ocean in the 20th century has already risen by 10-20 cm.) It has been established that a 1 mm rise in sea level leads to a retreat of the coastline by 1.5 m.
If the sea level rises by about 1 m (and this is the worst scenario), then by 2100 about 1% of the territory of Egypt, 6% of the territory of the Netherlands, 17.5% of the territory of Bangladesh and 80% of the Majuro Atoll, which is part of the Marshal, will be under water - fishing islands. This will be the beginning of a tragedy for 46 million people. According to the most pessimistic forecasts, the rise in the level of the World Ocean in the XXI century. may entail the disappearance from the world map of countries such as Holland, Pakistan and Israel, the flooding of most of Japan and some other island states. St. Petersburg, New York and Washington may go under water. While some parts of the land are at risk of being at the bottom of the sea, others will suffer from the most severe drought. Disappearance threatens the Azov and Aral seas and many rivers. The area of deserts will increase.
A group of Swedish climatologists found that from 1978 to 1995 the area of floating ice in the Northern Arctic Ocean decreased by about 610 thousand km2, i.e. by 5.7%. At the same time, it turned out that through the Fram Strait, which separates the Svalbard (Spitsbergen) archipelago from Greenland, every year average speed about 15 cm/s into the open Atlantic up to 2600 km 3 floating ice(which is about 15-20 times the flow of a river like the Congo).
In July 2002, from a small island nation Tuvalu, located on nine atolls in the southern part Pacific Ocean(26 km 2, 11.5 thousand inhabitants), there was a call for help. Tuvalu is slowly but surely submerged - the highest point in the state rises only 5 m above sea level. electronic means The media have circulated a statement that the expected high tidal waves associated with the new moon could raise sea levels in the area by more than 3 m for some time, due to rising ocean levels due to global warming. If this trend continues, the tiny state will be washed off the face of the Earth. The government of Tuvalu is taking measures to resettle citizens in the neighboring state of Niue.
An increase in temperature will cause a decrease in soil moisture in many regions of the Earth. Droughts and typhoons will become commonplace. The ice cover of the Arctic will be reduced by 15%. In the coming century, the ice cover of rivers and lakes in the Northern Hemisphere will be 2 weeks less than in the 20th century. Ice melts in the mountains South America, Africa, China and Tibet.
Global warming will also affect the state of the world's forests. Forest vegetation, as is known, can exist within very narrow limits of temperature and humidity. Most of it may die, the complex ecological system will be at the stage of destruction, and this will entail a catastrophic decrease in the genetic diversity of plants. As a result of global warming on Earth in the second half of the XXI century. may disappear from a quarter to half of the species of land flora and fauna. Even under the most favorable conditions, by the middle of the century, the immediate threat of extinction will hang over almost 10% of the species of land animals and plants.
Studies have shown that in order to avoid a global catastrophe, it is necessary to reduce carbon emissions into the atmosphere to 2 billion tons per year (one third of the current volume). Given the natural population growth, by 2030-2050. per capita should be no more than 1/8 of the amount of carbon emitted today on average per inhabitant of Europe.
