Effects of feedback

[edit] Effects of feedback
Elements of the cause of global warming is also influenced by various feedback processes that result. An example is the evaporation of water. In the case of gas heating due to increasing greenhouse-gases such as CO2, warming will initially lead to more number of water evaporating into the atmosphere. Because water vapor is itself a greenhouse gas, warming will continue and increase the amount of water vapor in the air until the achievement of an equilibrium concentration of water vapor. Greenhouse effect produced greater than the effect of CO2 alone. (Although this feedback increases the absolute water content in the air, the air relative humidity is almost constant or even slightly decreased because the air becomes warmer). [3] This feedback effect is only slowly because CO2 has a long age in the atmosphere.

Feedback effect due to the influence of clouds is the object of current research. When viewed from below, clouds will reflect infrared radiation back to the surface, thereby increasing the heating effect. In contrast when viewed from above, these clouds will reflect sunlight and infrared radiation into space, thereby increasing the cooling effect. Is it the net effect of producing heating or cooling depending on some specific details such as the type and height of the cloud. The details are difficult to be represented in climate models, partly because the cloud is very small compared with the distance between computational limits of climate models (about 125 to 500 km for the model used in the IPCC report to view Four). Nevertheless, cloud feedback ranked second when compared with the water vapor feedback and is considered a positive (warming increase) in all models used in the IPCC report into the Four Views. [3]

Another important feedback is the loss of ability to reflect light (Albedo) by the ice. [4] As global temperatures increase, ice near the poles to melt with increasing speed. Along with the melting of the ice, land or water below it will open. Both land and water have the ability to reflect light much less when compared with the ice, and consequently will absorb more sun radiation. This will increase the warming and cause more ice to melt, into a continuous cycle.

Positive feedback due to release of CO2 and CH4 from the softening of frozen soil (permafrost) are other mechanisms that contribute to warming. In addition, the melting ice will also release CH4 is also causing a positive feedback.

Ocean's ability to absorb carbon will also be reduced if it warms, it menurunya caused by nutrient levels in the mesopelagic zone of limiting the growth of diatoms than the phytoplankton, which is a low carbon sinks. [5]

[edit] Solar variation

Solar variation over 30 years terakhir.Artikel Main is: Variations Sun
There is a hypothesis which states that the variation of the Sun, with a possibility reinforced by feedback from clouds, can contribute in the current warming. [6] The difference between this mechanism with the warming due to greenhouse effect is the increased activity of the Sun would heat the stratosphere instead of greenhouse effect will cool the stratosphere. Cooling of the lower stratosphere has been observed at least since 1960, [7] are not going to happen when the activity of the Sun to be the main contributor to this warming. (Thinning of the ozone layer can also provide the cooling effect but the depletion occurred from the late 1970s.) Phenomenon, combined with variations in the Sun volcanic activity may have provided the heating effect of pre-industrial times until 1950, and the cooling effect since 1950 . [8] [9]

There are several studies stating that the contribution of the Sun may have been overlooked in global warming. Two scientists from Duke University estimated that the Sun may have contributed to 45-50% increase in average temperatures globally during the period 1900-2000, and approximately 25-35% between 1980 and 2000. [10] Stott and his colleagues argue that climate models guiding the current estimate of the effect of excessive gas-greenhouse gases compared with the effects of the sun, they also noted that the cooling effects of volcanic ash and sulfate aerosols have also been considered trivial. [11] Nevertheless, they concluded that even with increased sensitivity The sun influences the climate though, most of the warming that occurred in the last decades is caused by the gas-greenhouse gases.

In 2006, a team of scientists from the United States, Germany and Switzerland stated that they found no increase in the level of "information" from the Sun in the last thousand years. Solar cycle gives only a small increase of about 0.07% in the level of "statement" during the last 30 years. This effect is too small to contribute to global pemansan. [12] [13] A study by Lockwood and Fröhlich found no relation between the variations of global warming since 1985, the Sun, either through a variation of the output of the Sun and the variations in cosmic rays. [ 14]