Greenhouse effect

Greenhouse effect

Human activity increases the greenhouse effect and leads to global warming.

Geography

Keywords

greenhouse effect, global warming, climate change, desertification, rise in sea level, heat absorption, reflection, incoming radiation, emitted radiation, atmospheric gases, greenhouse gas, carbon dioxide, methane, nitrogen oxide, water vapour, agriculture, industry, transportation, human activity, atmosphere, air, Earth, sea level, Sun, cloud, settlement, waste, glacier, society, nature, geography

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Scenes

Greenhouse

Most of the short-wave solar radiation passes through the Earth's atmosphere unhindered, it is then absorbed by the surface, thus increasing its temperature. Warm surfaces emit long-wave thermal radiation, which is absorbed by the atmosphere.
Therefore a significant part of the emitted heat is held back by the atmosphere – that is, not the air itself, but its water vapour and greenhouse gas content. The greenhouse effect is based on the heat retaining capacity of the atmosphere.

The name comes from the greenhouses used in agriculture, where a similar process occurs. In these greenhouses it is the glass or plastic covering that retains the heat.

If there were no natural greenhouse effect on Earth, the average temperature would be 35 °C lower than at present, our planet would be covered with ice, with an average temperature of -20 °C. When the amount of greenhouse gases in the atmosphere increases, the average temperature on Earth rises.

The majority of the gases responsible for the greenhouse effect, such as water vapours, carbon dioxide, methane and nitrous oxide, are naturally found in the atmosphere. Over the past 100 years, however, a number of gases have either appeared in the atmosphere that, normally, would not be found in the atmosphere naturally or the percentage of these gases has increased. All these enhance the greenhouse effect, which causes more heat to be trapped in the atmosphere.

As a result of climate change and global warming the polar ice sheets have started to melt, which has caused a rise in sea levels. This has posed a threat to many coastal towns. The number of storms and hurricanes is increasing, the weather is becoming unpredictable, desertification has become common, forest fires are more frequent and many species of animals have become endangered.

As the Earth warms, the size of permanently frozen areas will decrease and methane will be released into the atmosphere. Since methane is a more potent greenhouse gas than carbon dioxide, it traps more heat. Methane found in permafrost areas accumulated in frozen mires during the last glacial period. As the permafrost melts, methane hydrate also melts and is released into the atmosphere. Overpressure caused by this escaping gas triggers an explosion in certain places in the ground, creating a crater. Methane is released in large amounts not only from the mainland but also from the melting sediment of polar seas. The rate of global warming will probably increase more rapidly as more methane is released into the atmosphere.

Definitions of terms:

Incoming radiation: Electromagnetic solar radiation reaching the Earth's surface. It is converted into thermal energy on the surface and contributes to the warming of the soil and the air (indirectly).

Reflection: Electromagnetic solar radiation is reflected into the interplanetary space by particles of water vapour, ice or pollution that are larger than the wavelength of the radiation.

Heat absorption: A small part of the incoming solar radiation is absorbed by the elements of the atmosphere, causing a very small degree of warming. Ozone absorbs ultraviolet radiation, while water vapour and carbon dioxide absorb infrared radiation.

Outgoing radiation: The Earth´s surface, warmed by incoming solar radiation, transmits heat to the air above by long-wave thermal radiation.

Greenhouse gases: Gases that play an important role in the greenhouse effect: carbon dioxide, methane, nitrogen oxides, freons and ozone in the troposphere.

Atmosphere

Natural greenhouse effect

Enhanced greenhouse effect

Melting of the ice sheets

Animation

Narration

The Earth receives high-energy, short-wavelength radiation from the Sun. A small portion of this electromagnetic radiation is reflected back into space; most of it, however, passes through the atmosphere, and thus reaches the Earth's surface.

On reaching the surface of the Earth, some of the sunlight is reflected back, while the rest is absorbed at the surface. Therefore the Earth warms up and radiates heat back into the atmosphere. This low-energy thermal radiation consists of long wavelengths and heats the air.
Greenhouse gases trap the radiated heat from the Earth's surface, so the sunlight is first absorbed and then re-radiated.

This process is similar to the processes that take place in a greenhouse, in which the glass surface serves the same function as the greenhouse gases. Once sunlight passes through the glass, it is absorbed by the ground and is radiated back in the form of heat.
This heat is trapped in the glasshouse, which causes a significant increase in temperature. If there were no natural greenhouse effect on the Earth, the average temperature would be 35 °C lower than it is at present.

The majority of the gases responsible for the greenhouse effect, such as water vapours, carbon dioxide, methane and nitrous oxide, are naturally found in the atmosphere. Over the past 100 years, however, a number of gases have either appeared in the atmosphere that, normally, would not be found in the atmosphere naturally or the percentage of these gases has increased. All these enhance the greenhouse effect, which causes more heat to be trapped in the atmosphere.
The combustion of oil, gas and coal generates large amounts of carbon dioxide. Power plants, industry and transport are also responsible for carbon dioxide generation. Deforestation is also an important factor in the rise of carbon dioxide concentration, because vegetation absorbs carbon dioxide.
The non-natural gases are generated mostly during industrial activities in the form of solvents, foaming agents, degreasers or insulating materials. Methane is produced as a result of decay processes associated with agricultural activities, such as rice cultivation and animal husbandry. Waste treatment and waste water treatment are also responsible for methane production. Nitrous oxide is formed when nitrogenous substances, such as fertilisers, are decomposed.

Some researchers contest the idea that the current climate change and global warming are strongly related to the significant increase in the concentrations of greenhouse gases. In their view, this is a natural process.

As a result of climate change and global warming the polar ice sheets have started to melt, which has caused a rise in sea levels. This has posed a threat to many coastal towns. The number of storms and hurricanes is increasing, the weather is becoming unpredictable, desertification has become common, forest fires are more frequent and many species of animals have become endangered.

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