Greenhouse effect


Contents:
What is global warming?
Mechanism of global warming
What are greenhouse gases?
Consequences of global warming
Solution of the problem
The dispute over the causes of the greenhouse effect



What is global warming?

The Earth has an atmosphere thicker than 1000 kilometers. The atmosphere contains the air mass, which retain and store heat coming from the Sun in the form of infrared radiation. The increase in surface temperature of the Earth resulting from the retention of solar energy by greenhouse gases is known as the greenhouse effect, as well as global warming.



Mechanism of global warming

Emitted radiation Sun's radiation Greenhouse gases which partly reflect the radiation coming from Earth Back radiation reflected from greenhouse gases Sun's radiation Earth's surface heated up by Sun's radiation and back radiation Diagram of the greenhouse effect
The mechanism of the greenhouse effect has been introduced in the diagram.
A large part of solar radiation (short-wave radiation with a wavelength of 0.1 to 4 m) is passed through the Earth's atmosphere and is absorbed by the Earth's surface, causing it to warm. As a result of warming of the Earth's surface, the emission of infrared radiation (long wave radiation with a wavelength of 4 to 80 mm) takes place. A large part of this radiation is absorbed by molecules of water, carbon dioxide and other gases as well as the fine water droplets in clouds, that exist in the atmosphere. Heat is now mainly transferred through the atmosphere back to the Earth's surface in the form of so-called back radiation and only partly in space. Back radiation heats the Earth's surface again, therefore it is the basic cause of the planet's greenhouse effect. The energy lost by the planet is less than energy ingested coming from the sun.
Thanks to the protective effect of the atmosphere against cooling down, Earth's average temperature is approx. + 15C. If the atmosphere did not contain greenhouse gases, the heated surface of the Earth would emit their energy into space, so that the average air temperature would be equal to approx. -17C.
As long as man does not contaminate the environment so severely, as is currently the case, the water vapor served the main role in the absorption of heat reflected from the Earth's surface. However, since tens of years now the role of other greenhouse gases is rapidly increasing due to human activity.





What are greenhouse gases?

Greenhouse gases are volatile chemical substances existing in the atmosphere, where the physical and chemical properties allows the retention and storage of thermal energy and its transfer to the surface of the Earth in the form of infrared back radiation.
Among more than 30 identified greenhouse gases, in the table below have been listed 5 most important ones because of the contribution to the greenhouse effect and the ability to absorb infrared radiation in comparison to carbon dioxide.

The share of the main greenhouse gases in global warming Methane 18% Carbon dioxide 50% CFCs 14% Nitrogen oxides 6% Ozone 12%

Carbon dioxide, thats share is 50%, plays the most important role in the formation of the greenhouse effect. Such a high share of CO2 to the greenhouse effect, despite the smallest absorption of infrared radiation efficiency, is possible due to its high content in the atmosphere, i.e. approx. 0.03% (volume content). The role of carbon dioxide to the greenhouse effect is still increasing, which is the result of human activity: CO2 emissions associated with the industry, combined with the rapid depletion of the forest cover. It is estimated that global CO2 emissions of approx. 1011 t / year. In the current century, the concentration of this gas has increased from approx. 270 ppm at the beginning of the twentieth century to 360 ppm in 80s.
Also, methane (CH4) has substantial share in the formation of the greenhouse effect - 18%. This gas is generated and is emitted to the atmosphere as a result of numerous reactions of anaerobic decomposition of the remains of plants and animals, as well as the anaerobic decomposition of manure. Methane is the major component of natural gas and therefore large quantities of it are released into the atmosphere together with the mined coal and oil.
CFCs, unlike other gases, which are placed in the graph above do not occur naturally. They are formed only through chemical reactions carried out by human (reaction between hydrogen fluoride and halogenated methane or ethane in the presence of a catalyst - antimony pentachloride) and are used in refrigeration and for the production of aerosols (now increasingly less often). CFCs are particularly dangerous gases, not only because of the very low chemical activity, resulting in theirs high stability. Compared to carbon dioxide, chlorofluorocarbons are 10 to 20,000 times more effective in absorbing infrared radiation. It should also be noted that CFCs cause decomposition of ozone (O3), oxygen (O2) is formed resulting in the ozone hole.
The share of ozone in the formation of the greenhouse effect is 12%. It is created in a natural way - from oxygen, due to lightning or ultraviolet radiation. Ozone exists in the lower atmosphere in small amounts (approx. 2 * 10-5 g / dm3). Its content is much higher in the upper layers of atmosphere (ozonosphere). It protects all living organisms on Earth from ultraviolet radiation.
Nitrogen oxides play the smallest role in causing the greenhouse effect among the gases listed in the table above and in the chart - 6%. They get to the environment mainly with exhaust fumes of cars and together with nitrogen fertilizers. The most effective oxide is N2O (150 times more effective than carbon dioxide), but its content in the atmosphere is equal to approx. 10-6%.

As a result of human activity the content of greenhouse gases in the atmosphere is steadily increasing, which leads to worsening of the greenhouse effect. We should consider the consequences of global warming on Earth. Are we threatened by ecological disaster?



Consequences of global warming

The effects of the gradual warming of the Earth's climate can be seen for many years. In many places on Earth, there is observed increase in average air temperature. The heated water in the seas and oceans cause the melting of glaciers on the Earth's poles and increase in volume, which leads to raise their level. Over the next fifty years it could lead to flooding of many areas located on low altitude. It is calculated that almost all area of the Netherlands, Denmark, Belgium and a large part of Bangladesh may be flooded as a result of melting glaciers in Greenland and Antarctica. On Polish territory floods may affect the area located at distance of up to 100 km from the coast of the Baltic Sea.
However, theoretically the increase the weight of glaciers could also be possible. As a result of global warming will increase evaporation of waters in the seas and oceans, which will lead to an increase in the amount of rainfall on Earth. In the surroundings of the poles of the planet, a snowfall can contribute to the rapid accumulation of glaciers. Unfortunately, such a phenomenon is currently not observed.
Much more likely is the shift in climate zones toward the poles on Earth. There may be many reasons for this. Excessive heating of air masses can lead to changes in the circulation of local and large-scale air currents above the surface of the globe. The greenhouse effect may also lead to changes in the system of ocean currents. It is not difficult to guess what will be the effects of the displacement of climatic zones. The new climate will lead to numerous natural disasters. The revised arrangements of atmospheric pressures will result in hurricanes, cyclones and tornadoes. The increased evaporation of water in the seas and oceans will lead to the occurrence of torrential rainfall, and hence, to the numerous floods and avalanches in the mountains. At the same time, droughts will persist as a result of the rapid drying of soils in areas located at significant distances from large bodies of water. Prolonged drought is often accompanied by forest fires. Burned biomass emits into the atmosphere huge amounts of smog containing CO2, CO, nitrogen oxides and other gases, and therefore additionally increase the intensity of the greenhouse effect.
Species of plants and animals that do not adapt to the changed conditions, simply will disappear from the face of the Earth. Many diseases are associated with a hot climate (e.g. malaria) may affect humans and animals, which are completely not resistant.

The effects of climate change due to the greenhouse effect can also be seen in the human economy, or more precisely - in agriculture. The chemical composition of the soil, characteristic of the zone climate does not change as rapidly as temperature and humidity. Therefore, there will be possible cultivation of plants in areas with at larger than previously latitudes, despite the favorable climatic conditions there, because the soil will be fertile. Agriculture will not be able to feed the constantly growing population.

The consequences of global warming on Earth are obvious - many people may die as a result of a growing number of natural disasters. Even more people may die from hunger and as a result of new diseases. The greenhouse effect is thus ecological problem which constitutes a real threat to humanity. Therefore, we should today seek solutions to this problem and to think about what to do in order to avoid the increasing of global warming.



Solutions of problem

As I mentioned on the main page, to solve contemporary problems of our environment, the efforts of one or several nations are not enough. The greenhouse effect is a threat to all mankind, and therefore, all people have to look for the solutions to this problem.
Every man can lead to reduction of the intensity of the greenhouse effect by e.g. segregation of garbage and the use of recycled materials. Thereby, one can reduce the emission of carbon dioxide, which accompanies the production of packaging, and also reduces the release of methane, that is produced during the decomposition of organic matter in landfills.
Society should save energy. The use of insulating materials in buildings makes it possible to protect against excessive loss of heat energy. Electricity can be saved through the use of modern, energy-efficient electrical appliances. In this way we can reduce energy demand, and thus will be possible to limit its production by heating plants and power plants. Thereby, emissions of carbon dioxide into the atmosphere can be reduced.
The efficiency of heat and power plants also must be observed. It is calculated that only 35% of the energy from the combustion of coal is utilized. The remaining 65% is dissipated mainly as heat. After the appropriate repairs of power would be possible to use this energy eg. to receive hot water serving the needs of industry or for heating residential buildings.
In order to reduce carbon dioxide emissions into the atmosphere alternative sources of energy should be searched. Also, the phenomenon of rapid decrease of amount of fossil fuels leads us to this search (it is calculated that global oil reserves run out for approx. 30 years, while coal seams will be exploited for approx. 170 years). Renewable energy resources in practice will never run out. These should involve: solar radiation, air movement, the movements of water in rivers, waves and tides, geothermal energy. The most important source of energy for the Earth is solar radiation. Along with the solar radiation to the Earth reaches the power of approx. 178 000 TW (1 TW = 100000 MW), of which approx. 30% is reflected by the atmosphere, more than 45% is absorbed by the land and sea in the form of heat, the rest is consumed in the cycle of hydrological processes of photosynthesis and propelling air and sea waves. For comparison, a medium-sized power plant burning between 1.5 and 2 million tons of coal by year has a power only 1000 MW.
A significant share of emissions of carbon dioxide and nitrogen oxide is generated from motor vehicles. To reduce greenhouse gas emissions from cars we should try to persuade the public to use public transport or other vehicles, that do not pollute the environment: bicycles.
Forests are the most important factor in regulating the carbon dioxide content in the atmosphere. It was calculated that one hectare of forest can absorb 250 kg of carbon dioxide. You should completely stop deforestation of equatorial and reduce the cutting and burning of remaining forests. You should also plant new trees in place of the cut ones.
The measures aimed at reducing carbon dioxide emissions into the atmosphere were discussed in June 1992 on the so-called. "Earth Summit" in Rio de Janeiro, Brazil. The authorities there have adopted the Framework Convention, which complements the so-called Montreal Protocol 1987 with resolutions on the reduction of emissions of CO2, CH4 and N2O.
Reducing emissions testifies to the fact that the nations are aware of the threat that the greenhouse effect is and try to counteract the increase of global warming.



The dispute over the causes of the greenhouse effect

Recently, controversy continues about the cause of the greenhouse effect. Many scientists from around the world claim that greenhouse gases emitted by human activities are of little significance in shaping the global air temperature. The global warming is considered to be caused by natural factors, such as increased solar activity or volcanic eruptions.