Greenhouse Effect, Its Mechanism And Importance

Greenhouse effect is process by which radiation from a planet’s atmosphere warms the planet’s surface to a temperature more than atmosphere

By Mussera tul-hira 

Greenhouse effect

The trapping of the sun’s warmth in a planet’s lower atmosphere, due to the greater transparency of the atmosphere to visible radiation from the sun than to infrared radiation emitted from the planet’s surface is known as green house effect. 

 The greenhouse effect is the process by which radiation from a planet’s atmosphere warms the planet’s surface to a temperature above what it would be without its atmosphere. 

If a planet’s atmosphere contains radioactively active gases (i.e., greenhouse gases) they will radiate energy in all directions. Part of this radiation is directed towards the surface, warming it. The intensity of the downward radiation – that is, the strength of the greenhouse effect – will depend on the atmosphere’s temperature and on the amount of greenhouse gases that the atmosphere contains. 

History:

The greenhouse effect was first discovered by Joseph Fourier in 1827, experimentally verified by John Tyndall in 1861, and quantified by Svante Arrhenius in 1896.

The 19th century French mathematician Joseph Fourier is usually credited as the originator of the idea in the 1820’s. However, it turns out he never used the term, and as James Fleming (1999) points out, most authors writing about the history of the greenhouse effect cite only secondary sources on this, without actually reading any of Fourier’s work.

Fourier does mention greenhouses in his 1822 classic “Analytical Theory of Heat”, but not in connection with planetary temperatures. 

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 Greenhouse Effect Mechanism

The sun radiates solar energy on earth. The larger part of this energy (45%) is radiated back into space. it contribute in the atmosphere to global warming by adsorption and reflection of atmospheric and solar energy.

This sunlight (shortwave radiation) passes into the planet’s atmosphere and warms the Earth. Part of this energy is absorbed by the Earth’s surface, transformed into heat (long wave radiation) and radiated back towards space. But as this heat goes up through the atmosphere, some of it is trapped by the different greenhouse gases and doesn’t escape into space. This in turn warms up the Earth’s atmosphere; just like the windows of a greenhouse that lets light in and keeps the heat within to warm the plants growing inside.

Since some of the heat can’t escape into space, it continues to add up which then warms up the Earth. So the more greenhouse gases you have in the atmosphere, the more heat stays on Earth. 

 Without the heating caused by this effect, Earth’s average surface temperature would be only about −18 °C (0 °F). On Venus the very high concentration of carbon dioxide in the atmosphere causes an extreme greenhouse effect resulting in surface temperatures as high as 450 °C (840 °F).

  • natural and anthropogenic greenhouse gases causing green house effect: 

Natural greenhouse gases

Anthropogenic emissions

H2O (water vapor)

CO2 (carbon dioxide)

CH4 (methane)

CH4 (methane)

CO2 (carbon dioxide)

N2O (nitrous oxide)

O3 (ozone)

 

N2O (nitrous oxide)

 

After the industrial revolution of the 1700’s the greenhouse effect was enhanced by greenhouse gas emissions of anthropogenic nature. The main source of anthropogenic greenhouse gas emissions is fossil fuel combustion. 

Evidence if existence of greenhouse effect:

If the amount of energy from the sun and the amount of greenhouse gases in the atmosphere remain the same, then the average temperature on Earth will also be constant. But this is no longer the case. The amount of greenhouse gases in our atmosphere is the highest it has been in the last 3 million years. This is enhancing the greenhouse effect and making the Earth warmer than normal, which is affecting the planet’s weather patterns, creating global warming and climate change.

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The greenhouse effect is caused by the interaction of the sun’s energy with greenhouse gases such as carbon dioxide, methane, nitrous oxide and fluorinated gases in the Earth’s atmosphere. The ability of these gases to trap heat is what causes this effect. 

Greenhouse gases are made of three or more atoms. This molecular structure makes it possible for these gases to trap heat in the atmosphere and then re-emit it towards the surface which further warms the Earth. This continuous cycle of trapping heat leads to an overall increase in global temperatures. This process, which is very similar to the way a greenhouse works, is why the gases that can produce this effect are collectively known as greenhouse gases.

The principal forcing gases of the greenhouse effect are:

The main feedback gas of the greenhouse effect is:

  • Water vapor

Carbon dioxide, methane, nitrous oxide and the fluorinated gases are all well-mixed gases in the atmosphere that do not react to changes in temperature and air pressure, so the levels of these gases are not affected by condensation. Water vapor on the other hand, is a highly active component of the climate system that responds rapidly to changes in conditions by either condensing into rain or snow, or evaporating to return to the atmosphere. Thus the impact of the greenhouse effect is primarily circulated through water vapor, and it acts as a fast feedback. 

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Increased greenhouse gases directly increase the heat on the planet’s surface and lower atmosphere. This has a rippling effect as it can thin and even create holes in the ozone layer. This means that other radiation like ultra violet (UV) rays can seep in from the Sun. 

Negative impacts of greenhouse effect:

Increasing greenhouse gas emissions from human activities are trapping more energy (due to the greenhouse effect) on earth leading to several negative effects.

The greenhouse effect itself is not inherently bad. It is the rapid increase in greenhouse gas (GHG) emissions from human activities that are causing problems. GHGs are trapping more energy (due to the greenhouse effect) on earth leading to several negative effects all connected to global warming (see image below). As more solar energy is trapped on earth, the planet warms and this warming is happening at a rapid pace. 

Positive effects of greenhouse effect:

The greenhouse effect is important, because it contributes to the survival of life on Earth. Without the greenhouse effect, the temperature of the planet would be similar to conditions experienced on the moon. On the lunar surface, with no atmosphere to mediate temperature swings, the surface can reach 134 degrees Celsius (273 degrees Fahrenheit) during the day and -153 degrees Celsius (-244 degrees Fahrenheit) at night.

This dramatic temperature change required NASA to develop specialized gear to protect astronauts from both extremes for the moon landings.

 Unfortunately, while a moderate greenhouse effect is vital to life but elevated can be dangerous. Since the Industrial Revolution, the widespread adoption of fossil fuels has increased the amount of carbon dioxide, water vapor, and other greenhouse gases in the atmosphere. Temperature swing on Earth would have produced an environment hostile to most living things.

 

Mussera tul-hira

Mussera tul-hira

My name is Mussera-tul-hira. I am from Sargodha, Pakistan. I have been traveling in search of knowledge and for study purposes. For now, I am at Agriculture University of Faisalabad for M.Phil in Botany. I did my B.S from University of Sargodha. I like studying and revealing nature of plants. Moreover, Pakistan is my most valuable asset. I am directly responsible for its betterment and trying to play my role for a better Pakistan.

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