The greenhouse effect It is a natural process in which the atmosphere retains part of the infrared radiation emitted by the Earth and thus heats it. This infrared radiation comes from the heating generated on the earth's surface by solar radiation.
This process occurs because the Earth as an opaque body absorbs solar radiation and emits heat. At the same time, since there is an atmosphere, the heat does not completely escape to outer space.
Part of the heat is absorbed and re-emitted in all directions by the gases that make up the atmosphere. Thus, the Earth maintains a certain thermal equilibrium that establishes an average temperature of 15 ºC, guaranteeing a variable range in which life can develop..
The term "greenhouse effect" is a simile with greenhouses for growing plants in climates where the ambient temperature is lower than required. In these grow houses, the plastic or glass roof allows the passage of sunlight but prevents the exit of heat.
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The greenhouse effect is fundamental for life on Earth, as it guarantees the appropriate temperature range for its existence. Most of the biochemical processes necessary for life require temperatures between -18ºC to 50ºC..
In the geological past, fluctuations have occurred in the earth's average temperature, either increasing or decreasing. In the last two centuries there has been a process of sustained increase in global temperature.
The difference is that currently the rate of increase is particularly high and seems to be associated with human activity. These activities generate greenhouse gases that accentuate the phenomenon.
The process by which the greenhouse effect is produced has as its main elements the Sun, the Earth and atmospheric gases. The Sun is the source of energy, the Earth the receiver of this energy and emitter of heat and gases..
The Sun fundamentally emits high-energy radiation, that is, corresponding to the visible and ultraviolet wavelengths of the electromagnetic spectrum. The emission temperature of this energy reaches 6,000 ºC, but most of it dissipates on the way to Earth.
Of the 100% of solar energy that reaches the atmosphere, about 30% is reflected to outer space (albedo effect). 20% is absorbed by the atmosphere, mainly by suspended particles and the ozone layer, and the remaining 50% warms the earth's surface.
The Earth reflects an important part of the solar radiation due to its albedo (light tone or whiteness). This albedo is mainly due to clouds, bodies of water and ice..
Taking into consideration the albedo and the distance from the planet to the Sun, the Earth's temperature should be -18 ºC (effective temperature). The effective temperature refers to what a body should have only considering albedo and distance.
However, the real average temperature of the Earth is around 15ºC with a difference of 33ºC with the effective temperature. In this marked difference between the actual and effective temperature, the atmosphere plays a fundamental role.
The key to the temperature of the Earth is its atmosphere, if it did not exist the planet would be permanently frozen. The atmosphere is transparent to much of the short-wave radiation, but not to a large proportion of the long-wave (infrared) radiation..
By letting solar radiation pass through, the Earth heats up and emits infrared radiation (heat), but the atmosphere absorbs some of that heat. In this way, the layers of the atmosphere and clouds are heated and emit heat in all directions..
The process of global warming due to the atmospheric retention of infrared radiation is what is known as the greenhouse effect.
The name comes from the agricultural greenhouses, where species are grown that require a higher temperature than that existing in the production area. For this, these grow houses have a roof that allows sunlight to pass through but retains the heat emitted..
In this way it is possible to create a warm microclimate for those species that require it in their growth..
Although the greenhouse effect is a natural process, it is altered by human action (anthropic action). Therefore, it is necessary to differentiate the natural causes of the phenomenon and the anthropic alterations.
Short-wave (high-energy) electromagnetic radiation from the Sun is what heats the Earth's surface. This heating causes the emission of long-wave radiation (infrared), that is, heat, into the atmosphere.
The center of the planet is incandescent and generates additional heat than that caused by solar energy. This heat is transmitted through the earth's crust mainly through volcanoes, fumaroles, geysers and other hot springs..
The properties of the gases that make up the atmosphere determine that solar radiation reaches the Earth and that infrared radiation is partially retained. Some gases such as water vapor, CO2 and methane are especially efficient at retaining atmospheric heat.
Those gases that retain infrared radiation from warming of the Earth's surface are called greenhouse gases. These gases are produced naturally, such as CO2 that is contributed by the respiration of living beings.
Likewise, the oceans exchange large amounts of CO2 with the atmosphere and natural fires also contribute CO2. The oceans are a natural source of other greenhouse gases such as nitrogen oxide (NOx).
On the other hand, microbial activity in soils is also a source of CO2 and NOx. In addition, the digestive processes of animals contribute large amounts of methane to the atmosphere.
Industry in general emits additional heat into the atmosphere, as well as various gases that affect the greenhouse effect. These gases can absorb and emit heat (ex: CO2) or destroy the ozone layer (ex: NOx, CFC and others).
Large concentrations of vehicles in cities are responsible for most of the CO2 added to the atmosphere. Automotive traffic contributes around 20% of the total CO2 generated by the burning of fossil fuels.
The burning of coal, gas and oil derivatives for the production of electricity and heating contributes almost 50% of the CO2.
Together, these industrial activities contribute almost 20% of the CO2 produced by burning fossil fuels..
Forest fires are also caused by human activities and annually release millions of tons of greenhouse gases into the atmosphere..
The accumulation of waste and the fermentation processes that occur, as well as the burning of said waste, are a source of greenhouse gases..
Agricultural activity contributes more than 3 million metric tons of methane gas annually to the atmosphere. Among the crops that contribute the most in this sense is rice.
Another crop whose management generates greenhouse gases is sugar cane, since it is burned before harvest and produces a large amount of CO2..
Ruminants like cows consume fibrous grass through fermentation processes carried out by bacteria in their digestive systems. This fermentation releases 3 to 4 liters of methane gas into the atmosphere daily for each animal..
Only considering cattle, a contribution equivalent to 5% of greenhouse gases is estimated.
The increase in global temperature that causes the increase in greenhouse gases, induces a chain reaction. As the temperature of the oceans increases, the release of CO2 into the atmosphere increases.
Likewise, the melting of the poles and permafrost releases CO2 that has been held there. Also at higher ambient temperatures, there is a greater occurrence of forest fires and more CO2 is released..
Some gases such as water vapor and CO2 act in the natural process of the greenhouse effect. For its part, other gases participate in the anthropic process in addition to CO2..
The Kyoto Protocol contemplates the emissions of six greenhouse gases, including carbon dioxide (CO2) and methane (CH4). Also, nitrous oxide (N2O), hydrofluorocarbon (HFC), perfluorinated hydrocarbon (PFC) and sulfur hexafluoride (SF6).
Water vapor is one of the most important greenhouse gases for its ability to absorb heat. However, equilibrium is generated because water in liquid and solid state reflects solar energy and cools the Earth..
Carbon dioxide is the main long-lived greenhouse gas in the atmosphere. This gas is responsible for 82% of the increase in the greenhouse effect that occurred in recent decades.
In 2017 the World Meteorological Organization reported a global CO2 concentration of 405.5 ppm. This represents an increase of 146% compared to the levels estimated for before 1750 (pre-industrial era).
Methane is the second most important greenhouse gas, contributing about 17% of the warming. 40% of methane is produced by natural sources, mainly wetlands, while the remaining 60% is generated by human activities.
These activities include ruminant farming, rice cultivation, fossil fuel exploitation and biomass combustion. In 2017, atmospheric CH4 reached a concentration of 1,859 ppm, which is 257% higher than the pre-industrial level..
NOx contribute to the destruction of stratospheric ozone, increasing the amount of ultraviolet radiation that penetrates the Earth. These gases originate from the industrial production of nitric acid and adipic acid as well as from the use of fertilizers..
By 2017, these gases reached an atmospheric concentration of 329.9 ppm, equivalent to 122% of the level estimated for the pre-industrial era..
CFC is a powerful greenhouse gas that damages stratospheric ozone and is regulated under the Montreal Protocol. However, in some countries such as China it is still used in various industrial processes.
These gases are used in various industrial applications to replace CFCs. However, HFCs also affect the ozone layer and have a very high active permanence in the atmosphere.
PFCs are produced in incineration facilities for the aluminum smelting process. Like HFCs, they have a high permanence in the atmosphere and affect the integrity of the stratospheric ozone layer..
This gas also has a negative effect on the ozone layer, as well as a high persistence in the atmosphere. It is used in high voltage equipment and in the production of magnesium.
Pollution produced by humans contributes extra amounts of greenhouse gases, breaking the natural dynamic balance. Although these amounts are much lower than those generated by nature, they are enough to break this balance..
This has serious consequences for the planetary thermal balance and in turn for life on Earth..
The increase in the concentration of greenhouse gases generates an increase in the global average temperature. In fact, the average global temperature is estimated to have risen 1.1 ° C since the pre-industrial era..
On the other hand, it has been indicated that the period from 2015 to 2019 has been the hottest on record so far.
The increase in temperature brings as a consequence the melting of polar ice and glaciers worldwide. This implies an increase in the sea level and the alteration of the marine currents..
Although there is no full agreement on the process of climate change resulting from global warming, the reality is that the planet's climate is changing. This is evidenced in the alteration of marine currents, wind patterns and rainfall, among other aspects..
The alteration of habitats due to the increase in temperature affects the population and biological behavior of the species. In some cases, there are species that increase their populations and broaden their range of distribution..
However, those species that have very narrow temperature ranges for their growth and reproduction can greatly reduce their populations..
Many agricultural and livestock areas see production reduced because the species are affected by the increase in temperature. On the other hand, ecological alterations result in the proliferation of agricultural pests.
As the planetary average temperature increases, some disease vector animals expand their geographic range. Thus, cases of tropical diseases are occurring beyond their natural range..
On the other hand, the increase in temperature can produce the so-called shock thermal or heat stroke, which implies extreme dehydration. This situation can cause serious organ failure, especially affecting children and the elderly..
To prevent the increase in the greenhouse effect, it is necessary to reduce the production of greenhouse gases. This implies a series of actions that include the development of citizen awareness, legislative measures, technological changes..
A citizenry aware of the problem of global warming generated by the increase in the greenhouse effect is fundamental. In this way, the necessary social pressure is provided so that governments and economic powers take the required measures..
The main international agreement to face the problem of greenhouse gas generation is the Kyoto Protocol. However, so far this legal instrument has not been effective in reducing the rate of greenhouse gas emissions..
Some of the main industrialized countries with the highest emission rates did not sign the extension of the protocol for its second term. Therefore, a stricter national and international legal framework is necessary if a real effect is to be achieved..
A reengineering of industrial processes is required in order to reduce greenhouse gas emissions. Similarly, it is necessary to promote the use of renewable energies and reduce the use of fossil fuels..
On the other hand, it is essential to reduce the production of polluting waste in general..
According to the experts, it is not enough to reduce greenhouse gas emissions, it is also necessary to reduce the current concentrations in the atmosphere. For this, various alternatives have been proposed that can use very simple or sophisticated technologies..
For this, it is recommended to increase the coverage of forests and jungles, as well as to implement strategies such as green roofs. Plants fix atmospheric CO2 in their plant structures, extracting it from the atmosphere.
Until now, extracting CO2 from the atmosphere is costly from an energy point of view and has a high economic cost. However, research is ongoing to find efficient ways to filter the air and remove CO2..
One of these proposals is already in the pilot plant phase and is being developed by the Universities of Calgary and Carnegie Mellon. This plant uses a solution of potassium hydroxide as an aqueous trap and caustic calcium, through which the air is filtered.
In this process, the CO2 contained in the air is being retained, forming calcium carbonate (CaCO3). Subsequently, the calcium carbonate is heated and the CO2 is released, applying the resulting purified CO2 for industrial uses..
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