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How CO 2 causes the greenhouse effect. Matter emits thermal radiation at a rate that is directly proportional to the fourth power of its temperature. Some of the radiation emitted by the Earth's surface is absorbed by greenhouse gases and clouds. Without this absorption, Earth's surface would have an average temperature of −18 °C (−0.4 °F).
Though water plays a major role in the process, the runaway greenhouse effect is not a result of water vapor feedback. [4] The runaway greenhouse effect can be seen as a limit on a planet's outgoing longwave radiation that, when surpassed, results in a state where water cannot exist in its liquid form (hence, the oceans have all "boiled away"). [3]
For other gases it depends on how strongly the gas absorbs thermal radiation, how quickly the gas leaves the atmosphere, and the time frame considered. For example, methane has a GWP over 20 years (GWP-20) of 81.2 [39] meaning that, a leak of a tonne of methane is equivalent to emitting 81.2 tonnes of carbon dioxide measured over 20 years. As ...
Thermal radiation is the emission of electromagnetic waves from all matter that has a temperature greater than absolute zero. [5] [2] Thermal radiation reflects the conversion of thermal energy into electromagnetic energy. Thermal energy is the kinetic energy of random movements of atoms and molecules in matter. It is present in all matter of ...
Although greenhouse gases in air have a high emissivity at some wavelengths, this does not necessarily correspond to a high rate of thermal radiation being emitted to space. This is because the atmosphere is generally much colder than the surface, and the rate at which longwave radiation is emitted scales as the fourth power of temperature.
Water vapor concentration for this gas mixture is 0.4%. Water vapor is a greenhouse gas in the Earth's atmosphere, responsible for 70% of the known absorption of incoming sunlight, particularly in the infrared region, and about 60% of the atmospheric absorption of thermal radiation by the Earth known as the greenhouse effect. [25]
The Planck response is the additional thermal radiation objects emit as they get warmer. Whether Planck response is a climate change feedback depends on the context. In climate science the Planck response can be treated as an intrinsic part of warming that is separate from radiative feedbacks and carbon cycle feedbacks.
Absorption cross sections for CO2 (green) and water vapour (purple). The wavelengths most relevant to climate change are those where the green plot crosses the upper horizontal line, representing a CO2 level somewhat larger than the current concentration. CO 2 absorbs the ground's thermal radiation mainly at wavelengths between 13 and 17 micron ...