Enhanced greenhouse effect
Definition (Encyclopedia of Global Warming)
Greenhouse gases (GHGs) in the atmosphere—such as carbon dioxide (CO2), methane, nitrous oxide, water vapor, and ozone—absorb infrared radiation from the Sun and reradiate some of it at the surface, warming Earth’s atmosphere. The average temperature of the atmosphere has been estimated to be more than 30° Celsius warmer than it would be without these gases. The natural greenhouse effect occurs when this process is the result of nonhuman activities; the enhanced greenhouse effect denotes increases in the effect caused by GHGs emitted into the atmosphere by human activities.
(The entire section is 91 words.)
Significance for Climate Change (Encyclopedia of Global Warming)
The concentrations of CO2 and, to a lesser extent, other GHGs have gradually increased in the atmosphere, especially during the twentieth century. For instance, the CO2 content of the atmosphere in the Hawaiian Islands has increased from 313 parts per million in 1960 to 375 parts per million in 2005. Arctic ice-core samples indicate that the CO2 content of the atmosphere has also gradually increased over longer timescales. Much of this increase in atmospheric CO2 concentration appears to be due to human activity, although the importance of human activity relative to natural processes such as in volcanism is not clear. It is known, however, that CO2 is released to the atmosphere by human activity, such as the burning of fossil fuels (petroleum, natural gas, and coal). Deforestation of tropical and other forests—such as the Amazon rain forest in Brazil—produces a great deal of CO2 as the plants decay, and it also reduces an extremely important carbon sink, increasing the amount of CO2 that remains in the atmosphere rather than being converted to biomass and oxygen. CO2 is also liberated in cement production.
A continued increase in GHGs will likely cause a continued increase in the average temperature of the atmosphere. The greatest increase in temperature will likely be over polar landmasses. For example, a doubling of the amount of CO2 in the atmosphere has been predicted to cause an average increase of...
(The entire section is 343 words.)