Green House Effect

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 Green House Effect

(ग्रीनहाउस प्रभाव)


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 this atmosphere.

Greenhouse gases--


The existence of the greenhouse effect, while not named as such, was proposed by Joseph Fourier in 1824.The argument and the evidence were further strengthened by Claude Pouillet in 1827 and 1838. John Tyndall was the first to measure the infrared absorption and emission of various gases and vapours. From 1859 onwards, he showed that the effect was due to a very small proportion of the atmosphere, with the main gases having no effect, and was largely due to water vapour, though small percentages of hydrocarbons and carbon dioxide had a significant effect.The effect was more fully quantified by Svante Arrhenius in 1896, who made the first quantitative prediction of global warming due to a hypothetical doubling of atmospheric carbon dioxide.However, the term "greenhouse" was not used to refer to this effect by any of these scientists; the term was first used in this way by Nils Gustaf Ekholm in 1901.

Earth receives energy from the Sun in the form of ultraviolet, visible, and near-infrared radiation. About 26% of the incoming solar energy is reflected to space by the atmosphere and clouds, and 19% is absorbed by the atmosphere and clouds. Most of the remaining energy is absorbed at the surface of Earth. Because the Earth's surface is colder than the Sun, it radiates at wavelengths that are much longer than the wavelengths that were absorbed. Most of this thermal radiation is absorbed by the atmosphere and warms it. The atmosphere also gains heat by sensible and latent heat fluxes from the surface. The atmosphere radiates energy both upwards and downwards; the part radiated downwards is absorbed by the surface of Earth. This leads to a higher equilibrium temperature than if the atmosphere did not radiate.


An ideal thermally conductive blackbody at the same distance from the Sun as Earth would have a temperature of about 5.3 °C (41.5 °F). However, because Earth reflects about 30% of the incoming sunlight, this idealized planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about −18 °C (0 °F).The surface temperature of this hypothetical planet is 33 °C (59 °F) below Earth's actual surface temperature of approximately 14 °C (57 °F).The greenhouse effect is the contribution of greenhouse gases to this difference.

Role in climate change

Strengthening of the greenhouse effect through human activities is known as the enhanced (or anthropogenic) greenhouse effect.This increase in radiative forcing from human activity is attributable mainly to increased atmospheric carbon dioxide levels.According to the 2014 Assessment Report from the Intergovernmental Panel on Climate Change, "atmospheric concentrations of carbon dioxide, methane and nitrous oxide are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century'".

CO
2 is produced by fossil fuel burning and other activities such as cement production and tropical deforestation.Measurements of CO
2 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.The current observed amount of CO
2 exceeds the geological record maxima (~300 ppm) from ice core data.The effect of combustion-produced carbon dioxide on the global climate, a special case of the greenhouse effect 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 carbon dioxide has varied from values as low as 180 ppm to the pre-industrial level of 270 ppm.Paleoclimatologists consider variations in carbon dioxide concentration to be a fundamental factor influencing climate variations over this time scale.



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Ecosystem

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चित्र
पारिस्थितिक तंत्र (Ecosystem) ■  प्रस्तावना -- पारिस्थितिक तंत्र को पारितंत्र भी कहा जाता हैै।  पारिस्थितिक तंत्र  शब्द का सर्वप्रथम प्रयोग   ब्रिटिश इकोलॉजिस्ट ए ▪ जी▪टेन्स्ले ( Arthur George Tansley) ने सन 1935 में किया था Arthur George Tansley ■ पारिस्थितिक तंत्र की परिभाषा-- जैविक  एवं अजैविक घटकों के पारस्परिक अंतर्संबंध को पारिस्थितिक तंत्र तथा पारिस्थितिक तन्त्र के अध्ययन को पारिस्थितिकी (Ecology) कहते हैं। ■   पारिस्थितिक तंत्र के घटक-- पारिस्थितिक तंत्र के दो घटक हैं-- 1) जैविक घटक 2) अजैविक या भौतिक घटक जैविक घटक  
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Science

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चित्र
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Hydroponics

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चित्र
  Hydroponics हीड्रोपोनिक्स  एक प्रकार की  बागवानी   है। इसमें पौधों को  जल में उगाया जाता है।   पौधों को  आम तौर पर  फसलों  को बिना  मिट्टी  का उपयोग करके  खनिज  पोषक तत्व को  एक जलीय  विलायक  मेें उगाया जाता है ।  
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