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Saturday, October 3, 2020

Greenhouse Effect

 The atmospheric phenomenon is that the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it might be without this atmosphere.

Earth's natural atmospheric phenomenon is critical to supporting life, and initially was a precursor to life moving out of the ocean ashore . Human activities, however, mainly the burning of fossil fuels and clearcutting of forests, have accelerated the atmospheric phenomenon and caused heating .

The term "greenhouse effect" continues to see use in scientific circles and the media despite being a slight misnomer, as an atmosphere reduces radiative heat loss while a greenhouse blocks convective heat loss. The result, however, is a rise in temperature in both cases.


Main article: History of climate change science

The existence of the atmospheric phenomenon , while not named intrinsically , was proposed by Joseph Fourier in 1824. The argument and therefore the evidence were further strengthened by Claude Pouillet in 1827 and 1838. John Tyndall was the primary to live the infrared absorption and emission of varied gases and vapours. From 1859 onwards, he showed that the effect was thanks to a really small proportion of the atmosphere, with the most gases having no effect, and was largely due to water vapor , though small percentages of hydrocarbons and CO2 had a big effect. However, the term "greenhouse" wasn't wont to ask this effect by any of those scientists; the term was first utilized in this manner by Nils Gustaf Ekholm in 1901.

Greenhouse gases

Main article: Greenhouse gas

By their percentage contribution to the atmospheric phenomenon on Earth the four major gases are:

Atmospheric gases only absorb some wavelengths of energy but are transparent to others. The absorption patterns of water vapour (blue peaks) and CO2 (pink peaks) overlap in some wavelengths. Carbon dioxide isn't as strong a greenhouse emission as water vapour , but it absorbs energy in longer wavelengths (12–15 micrometers) that water vapour doesn't , partially closing the "window" through which heat radiated by the surface would normally escape to space. (Illustration NASA, Robert Rohde)

water vapor, 36–70%

carbon dioxide, 9–26%

methane, 4–9%

ozone, 3–7%

It is impossible to assign a selected percentage to every gas because the absorption and emission bands of the gases overlap (hence the ranges given above). Clouds also absorb and emit infrared and thus affect the radiative properties of the atmosphere.

Role in climate change

Main article: Global warming

The Keeling Curve of atmospheric CO2 concentrations measured at Mauna Loa Observatory.

Strengthening of the atmospheric phenomenon through human activities is understood because the enhanced (or anthropogenic) atmospheric phenomenon . This increase in radiative forcing from act is attributable mainly to increased atmospheric CO2 levels. According to the 2014 Assessment Report from the Intergovernmental Panel on global climate change , "atmospheric concentrations of CO2 , methane and laughing gas are unprecedented in a minimum of the last 800,000 years. Their effects, along side those of other anthropogenic drivers, are detected throughout the climate system and are extremely likely to possess been the dominant explanation for the observed warming since the mid-20th century'".

CO2 is produced by fuel burning and other activities like cement production and tropical deforestation. 

Measurements of CO2 from the Mauna Loa observatory show that concentrations have increased from about 313 parts per million (ppm) in 1960, passing the 400 ppm milestone on May 9, 2013.[30] the present observed amount of CO2 exceeds the geological record maxima (~300 ppm) from ice core data. The effect of combustion-produced CO2 on the worldwide climate, a special case of the atmospheric phenomenon first described in 1896 by Svante Arrhenius, has also been called the Callendar effect.

Over the past 800,000 years, ice core data shows that CO2 has varied from values as low as 180 ppm to the pre-industrial level of 270 ppm. Paleoclimatologists consider variations in CO2 concentration to be a fundamental factor influencing climate variations over this point scale.

Real greenhouses

A modern Greenhouse in RHS Wisley

The "greenhouse effect" of the atmosphere is known as by analogy to greenhouses which become warmer in sunlight. However, a greenhouse isn't primarily warmed by the "greenhouse effect". "Greenhouse effect" is actually a misnomer since heating in the usual greenhouse is due to the reduction of convection, while the "greenhouse effect" works by preventing absorbed heat from leaving the structure through radiative transfer.

A greenhouse is made of any material that passes sunlight: usually glass or plastic. The sun warms the bottom and contents inside a bit like the surface , and these then warm the air. Outside, the nice and cozy air near the surface rises and mixes with cooler air aloft, keeping the temperature less than inside, where the air continues to heat up because it is confined within the greenhouse.

Heated greenhouses are yet one more matter: as they need an indoor source of heating, it's desirable to minimise the quantity of warmth leaking out by radiative cooling. This can be done through the utilization of adequate glazing.


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