File Name: greenhouse gases and its effects .zip
- Greenhouse effect
- GREENHOUSE EFFECT
- Effects of Greenhouse Gas Emissions on World Agriculture, Food Consumption, and Economic Welfare
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. Radiatively active gases i.
Part of this radiation is directed towards the surface, thus warming it. The temperature rises until the intensity of upward radiation from the surface, thus cooling it, balances the downward flow of energy. Earth's natural greenhouse effect is critical to supporting life, and initially was a precursor to life moving out of the ocean onto land. Human activities, mainly the burning of fossil fuels and clearcutting of forests, have increased the greenhouse effect and caused global warming.
The term greenhouse effect is a slight misnomer , in the sense that physical greenhouses warm via a different mechanism. The greenhouse effect as an atmospheric mechanism functions through radiative heat loss  while a traditional greenhouse as a built structure blocks convective heat loss. The existence of the greenhouse effect, while not named as such, was proposed by Joseph Fourier in John Tyndall was the first to measure the infrared absorption and emission of various gases and vapours.
From 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.
Earth receives energy from the Sun in the form of ultraviolet , visible , and near-infrared radiation.
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. The idealized greenhouse model is a simplification. In reality the atmosphere near the Earth's surface is largely opaque to thermal radiation and most heat loss from the surface is by convection.
However radiative energy losses become increasingly important higher in the atmosphere, largely because of the decreasing concentration of water vapor, an important greenhouse gas. Rather than the surface itself, it is more realistic to think of the greenhouse effect as applying to a layer in the mid- troposphere , which is effectively coupled to the surface by a lapse rate.
A simple picture also assumes a steady state, but in the real world, the diurnal cycle as well as the seasonal cycle and weather disturbances complicate matters. Solar heating applies only during daytime. During the night, the atmosphere cools somewhat, but not greatly, because its emissivity is low. Diurnal temperature changes decrease with height in the atmosphere. Within the region where radiative effects are important, the description given by the idealized greenhouse model becomes realistic.
It reradiates in all directions, both upwards and downwards; in equilibrium by definition the same amount as it has absorbed. This results in more warmth below. Increasing the concentration of the gases increases the amount of absorption and reradiation, and thereby further warms the layers and ultimately the surface below.
Greenhouse gases—including most diatomic gases with two different atoms such as carbon monoxide, CO and all gases with three or more atoms—are able to absorb and emit infrared radiation. By their percentage contribution to the greenhouse effect on Earth the four major gases are:  . It is not possible to assign a specific percentage to each gas because the absorption and emission bands of the gases overlap hence the ranges given above.
Clouds also absorb and emit infrared radiation and thus affect the radiative properties of the atmosphere. Strengthening of the greenhouse effect through human activities is known as the enhanced or anthropogenic greenhouse effect.
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 midth century'". CO 2 is produced by fossil fuel burning and other activities such as cement production and tropical deforestation. Over the past , years,  ice core data shows that carbon dioxide has varied from values as low as ppm to the pre-industrial level of ppm.
The "greenhouse effect" of the atmosphere is named by analogy to greenhouses which become warmer in sunlight. However, a greenhouse is not primarily warmed by the "greenhouse effect".
A greenhouse is built of any material that passes sunlight: usually glass or plastic. The sun warms the ground and contents inside just like the outside, and these then warm the air. Outside, the warm air near the surface rises and mixes with cooler air aloft, keeping the temperature lower than inside, where the air continues to heat up because it is confined within the greenhouse. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature will drop considerably.
It was demonstrated experimentally R. Wood , that a not heated "greenhouse" with a cover of rock salt which is transparent to infrared heats up an enclosure similarly to one with a glass cover. Heated greenhouses are yet another matter: as they have an internal source of heating, it is desirable to minimise the amount of heat leaking out by radiative cooling. This can be done through the use of adequate glazing.
It is possible in theory to build a greenhouse which lowers its thermal emissivity during dark hours;  such a greenhouse would trap heat by two different physical mechanisms, combining multiple greenhouse effects, one of which more closely resembles the atmospheric mechanism, rendering the misnomer debate moot.
The anti-greenhouse effect is a mechanism similar and symmetrical to the greenhouse effect: in the greenhouse effect, the atmosphere lets radiation in while not letting thermal radiation out, thus warming the body surface; in the anti-greenhouse effect, the atmosphere keeps radiation out while letting thermal radiation out, which lowers the equilibrium surface temperature.
Such an effect has been proposed for Saturn 's moon Titan. A runaway greenhouse effect occurs if positive feedbacks lead to the evaporation of all greenhouse gases into the atmosphere. Titan is a body with both a greenhouse effect and an anti-greenhouse effect. The presence of N 2 , CH 4 , and H 2 in the atmosphere contribute to a greenhouse effect, increasing the surface temperature by 21K over the expected temperature of the body with no atmosphere.
The existence of a high-altitude haze, which absorbs wavelengths of solar radiation but is transparent to infrared, contribute to an anti-greenhouse effect of approximately 9K. From Wikipedia, the free encyclopedia. Atmosopheric phenomenon. For other uses, see Greenhouse disambiguation.
Main article: History of climate change science. Main article: Greenhouse gas. Main article: Global warming. See also: Illustrative model of greenhouse effect on climate change. See also: Anti-greenhouse effect. See also: runaway greenhouse effect. Global warming portal Environment portal. Intergovernmental Panel on Climate Change.
Retrieved 10 October Because the Earth is much colder than the Sun, it radiates at much longer wavelengths, primarily in the infrared part of the spectrum see Figure 1. Much of this thermal radiation emitted by the land and ocean is absorbed by the atmosphere, including clouds, and reradiated back to Earth. This is called the greenhouse effect. In Bengtsson, Lennart O.
Geosphere-biosphere Interactions and Climate. Cambridge University Press. Claussen, E. University of Michigan. Allaby, A. A Dictionary of Earth Sciences.
Oxford University Press. MIT Press. Retrieved 14 December Journal of Geophysical Research: Planets. Bibcode : JGRE..
New Scientist. In Beatty, J. Boston: Sky Publishing. An introduction to thermal physics. Philosophical Magazine. In order to eliminate this action the sunlight was first passed through a glass plate. This shows us that the loss of temperature of the ground by radiation is very small in comparison to the loss by convection, in other words that we gain very little from the circumstance that the radiation is trapped.
Physics of climate. New York: American Institute of Physics. Annales de Chimie et de Physique in French. November Annual Review of Energy and the Environment. Retrieved 11 November Quarterly Journal of the Royal Meteorological Society.
Retrieved 15 October The Greenhouse Effect".
Human action is causing an increase in global temperature. For that reason, the greenhouse effect, far from being our great ally as was the case in the past, is now a risk to our survival. The flooding of coastal cities, the desertification of fertile areas, the melting of glacial masses and the proliferation of devastating hurricanes are just some of the main consequences. Global warming is having a profound impact on the processes of soil degradation and is contributing to the desertification of the most arid areas on the planet. The increase in the global temperature of the planet produces a rise in the level of the sea, which will cause the disappearance of islands and coastal cities. The greenhouse effect is a natural phenomenon and is beneficial for us.
Effects of Greenhouse Gas Emissions on World Agriculture, Food Consumption, and Economic Welfare
Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. In simplest terms, "greenhouse gases" let sunlight through to the earth's surface while trapping "outbound" radiation. This alters the radiative balance of the earth see Figure A. The greenhouse gases in the atmosphere act in much the same way as the glass panels of a greenhouse, which allow sunlight through and trap heat inside.
Of those gases, known as greenhouse gases , water vapour has the largest effect. The origins of the term greenhouse effect are unclear. Fourier, however, neither used the term greenhouse effect nor credited atmospheric gases with keeping Earth warm.
The consequences of the greenhouse effect: from desertification to floods
Because of many uncertainties, quantitative estimates of agriculturally related economic impacts of greenhouse gas emissions are often given low confidence. A major source of uncertainty is our inability to accurately project future changes in economic activity, emissions, and climate. This paper focuses on two issues. First, to what extent do variable projections of climate generate uncertainty in agriculturally related economic impacts? Second, to what extent do agriculturally related economic impacts of greenhouse gas emissions depend on economic conditions at the time of impacts? Results indicate that uncertainty due to variable projections of climate is fairly large for most of the economic effects evaluated in this analysis.
Greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons CFCs. The absorbed energy warms the atmosphere and the surface of the Earth. The problem we now face is that human activities — particularly burning fossil fuels coal, oil and natural gas , agriculture and land clearing — are increasing the concentrations of greenhouse gases. This is the enhanced greenhouse effect, which is contributing to warming of the Earth. Step 1: Solar radiation reaches the Earth's atmosphere - some of this is reflected back into space. Step 2: The rest of the sun's energy is absorbed by the land and the oceans, heating the Earth. Step 4: Some of this heat is trapped by greenhouse gases in the atmosphere, keeping the Earth warm enough to sustain life.