Read here. Climate models have been programmed to produce a thawing of the tundra permafrost from human CO2-induced warming. This tundra "melting" will produce an explosion of CO2 and methane gas into the atmosphere. This is the mighty lore of the AGW hypothesis, thus models must be instructed to simulate this outcome. Fortunately, the AGW hypothesis and climate model programmers were wrong - like big time.
Turns out that Arctic warming encourages growth of vegetation, especially dense, ground covering shrubs, which cause the ground to be shaded (go figure). As a result, the permafrost does not thaw as expected and large amounts of greenhouse gases are not released. Voilà, a natural negative feedback!
""Permafrost temperature records, however, do not show a general warming trend during the last decade, despite large increases in surface air temperature. Data from several Siberian Arctic permafrost stations do not show a discernible trend between 1991 and 2000. Our results suggest that an expansion of deciduous shrubs in the Arctic triggered by climate warming may buffer permafrost from warming resulting from higher air temperatures.”....Blok et al. conclude “These results suggest that the expected expansion of deciduous shrubs in the Arctic region, triggered by climate warming, may reduce summer permafrost thaw. Increased shrub growth may thus partially offset further permafrost degradation by future temperature increases. Permafrost models need to include a dynamic vegetation component to accurately predict future permafrost thaw.”"
