Two types of feedbacks that have substantial effects on climate change are the melting of permafrost and water vapor feedback. Both of these feedbacks are considered to be positive feedbacks, which implies that they amplify warming.
Permafrost is permanently frozen soil that stores massive amounts of carbon. Permafrost occurs mostly in high latitudes, and comprises of approximately 24% of the land in the Northern Hemisphere. As temperatures increases as the result of climate change, permafrost, which is made up of dead organic plant matter frozen into the soil that has yet to decay, is at risk of melting and releasing the stored carbon (that is hundreds to thousands of years old) as carbon dioxide and methane (which are powerful greenhouse gases). Studies have shown that there has been a decrease in freezing during the cold season and an increase in the thawing of permafrost, which suggests that more permafrost is melting seasonally instead of staying permanently frozen. Therefore, if a warming climate leads to the melting of permafrost, then the organic matter in it thaws out and decays, releasing the
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Thus, a warming of the surface increases atmospheric humidity and because water vapor itself is a greenhouse gas, this leads to additional warming. To put it another way, as temperature rises, evaporation increases and more water vapor accumulates in the atmosphere. Water vapor as a green house gas absorbs more heat, further warming the air and causing more evaporation. Water vapor is a positive feedback because it amplifies the initial warming. The effects of the water vapor feedback are considered to be fast feedbacks because they occur rapidly in response to a change in surface temperature and therefore its impact on energy in and energy out are nearly instantaneous. Therefore, the water vapor feedback is a significant feedback because its effects are rapidly taken into