| 释义 |
greenhouse effect
Physics
1. The effect within a greenhouse in which solar radiation mainly in the visible range of the spectrum passes through the glass roof and walls and is absorbed by the floor, earth, and contents, which re-emit the energy as infrared radiation. Because the infrared radiation cannot escape through the glass, the temperature inside the greenhouse rises. 2. A similar effect in which the earth’s atmosphere behaves like the greenhouse and the surface of the earth absorbs most of the solar radiation, re-emitting it as infrared radiation. This is absorbed by carbon dioxide, water, and ozone in the atmosphere as well as by clouds and reradiated back to earth. At night this absorption prevents the temperature falling rapidly after a hot day, especially in regions with a high atmospheric water content. It is thought that increased amounts of carbon dioxide in the atmosphere as a result of burning fossil fuels has increased the effect and contributed to global warming.
Astronomy
The elevation of a planet’s surface temperature resulting from the absorption of long-wavelength (infrared) radiation by gases in the atmosphere. For instance, carbon dioxide, methane, chlorofluorocarbons, and water vapour in the Earth’s atmosphere are all transparent to incoming short-wavelength solar radiation, but absorb outgoing infrared. The Earth is, on average, about 35 K warmer than it would be if its atmosphere were completely transparent to outgoing infrared. On Venus, the greenhouse effect raises the surface temperature by some 500 K to around 730 K.
Chemistry
An effect occurring in the atmosphere because of the presence of certain gases (greenhouse gases) that absorb infrared radiation. Light and ultraviolet radiation from the sun are able to penetrate the atmosphere and warm the earth’s surface. This energy is re-radiated as infrared radiation, which, because of its longer wavelength, is absorbed by such substances as carbon dioxide. Emissions of carbon dioxide from human activities have increased markedly in the last 150 years or so. The overall effect is that the average temperature of the earth and its atmosphere is increasing (so-called global warming). The effect is similar to that occurring in a greenhouse, where light and long-wavelength ultraviolet radiation can pass through the glass into the greenhouse but the infrared radiation is absorbed by the glass and part of it is re-radiated into the greenhouse. The greenhouse effect is seen as a major environmental hazard. Average increases in temperature are likely to change weather patterns and agricultural output. It is already causing the polar ice caps to melt, with a corresponding rise in sea level. Carbon dioxide, from fossil-fuel power stations and car exhausts, is the main greenhouse gas. Other contributory pollutants are nitrogen oxides, ozone, methane, and chlorofluorocarbons.
Chemical Engineering
A phenomenon in which the Earth’s atmosphere and surface is steadily heating up. It is caused by the ability of certain gases and particles in the Earth’s atmosphere to trap infrared radiation from the sun reflected back from the Earth’s surface more effectively than nitrogen and oxygen in air. The principal greenhouse gases are water vapour, carbon dioxide, methane, nitrous oxides, chlorofluorocarbons (CFCs), and ozone. Fossil fuel combustion is the main cause of carbon dioxide release, while methane is a by-product of agriculture and landfills. CFCs are even more potent but their use has been reduced in recent times. The levels of carbon dioxide and other greenhouses gases have been steadily increasing over the past century. It is thought that the level of carbon dioxide is due to industrialization and the burning of fossil fuels has led to the greenhouse effect, contributing to global warming. See global warming potential.
Biology
An effect occurring in the atmosphere because of the presence of certain gases (greenhouse gases) that absorb infrared radiation. Light and ultraviolet radiation from the sun are able to penetrate the atmosphere and warm the earth’s surface. This energy is re-radiated as infrared radiation, which, because of its longer wavelength, is absorbed by such substances as carbon dioxide. The greenhouse effect is a natural phenomenon, without which the earth’s climate would be much more hostile to life. However, emissions of carbon dioxide from human activities (e.g. farming, industry, and transport) have increased markedly in the last 150 years or so. The overall effect is that the average temperature of the earth and its atmosphere is increasing (so-called global warming). The effect is similar to that occurring in a greenhouse, where light and long-wavelength ultraviolet radiation can pass through the glass into the greenhouse but the infrared radiation is absorbed by the glass and part of it is re-radiated into the greenhouse. The greenhouse effect is seen as a major environmental hazard. Average increases in temperature are already changing weather patterns, affecting agricultural output (see climate change), and causing the polar ice caps to melt, with a corresponding rise in sea level. Carbon dioxide, emitted e.g. from coal-fired power stations and car exhausts, is the main greenhouse gas. Other contributory pollutants are nitrogen oxides, ozone, methane, and chlorofluorocarbons. Many countries have now agreed targets to limit emissions of greenhouse gases, e.g. by switching to renewable energy sources. See also pollution. http://www.bbc.co.uk/climate/evidence/greenhouse_effect_img.shtml https://www.livescience.com/37743-greenhouse-effect.html Summary of the greenhouse effect, from the Live Science website
Geology and Earth Sciences
The effect of heat retention in the lower atmosphere as a result of absorption and reradiation by clouds and gases (e.g. water vapour, carbon dioxide, methane, and chlorofluorocarbons) of long-wave (more than 4 μm) terrestrial radiation. The insulating effect is analogous to that of greenhouse glass (i.e. it is transparent to incoming short-wave radiation but partly opaque to reradiated long-wave radiation, although air in a greenhouse heats because it is unable to leave the building so the analogy is in a sense misleading) and alters the balance of incoming and outgoing radiation in the Earth’s energy budget. Increases in the concentration of atmospheric carbon dioxide, generated for example by the combustion of fossil fuels, will result in a global increase of atmospheric temperatures if not offset by other (perhaps natural) changes. In the absence of any feedback effects, a doubling of atmospheric carbon dioxide will produce a rise in temperature of 1 °C. See also atmospheric ‘window’.
Geography
The warming of the atmosphere as some of its gases absorb the heat given out by the Earth. Short-wave radiation from the sun warms the Earth during daylight hours, but this heat is balanced by outgoing long-wave radiation over the entire 24-hour period. Much of this radiation is absorbed by atmospheric gases, most notably water vapour, carbon dioxide, and ozone, but also by methane and chloro-fluorocarbons. All of these may be called greenhouse gases. Without this absorption, which is also known as counter-radiation, the temperature of the atmosphere would fall by 30–40 °C. This is the natural greenhouse effect. Through human agency, such as the clearance of rain forest, or the increased rearing of livestock, the concentration of greenhouse gases in the atmosphere is increasing. This is the enhanced greenhouse effect. Measurements taken at Mauna Loa, Hawaii, show that the concentration of atmospheric CO2, for example, increased by 19.4% between 1959 and 2004. It would follow, therefore, that increased concentrations of such greenhouse gases would lead to a rise in global temperatures; see global warming. http://cdiac.ornl.gov/ The Carbon Dioxide Information Analysis Centre.
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