The list of positive feedbacks, mechanisms demonstrated or hypothetical in which increase of avg. temps would cause release of more GHG, causing more warming etc. in a run-away loop,...is a long and scary list that includes thawing tundra and peat bogs, boiling methane hydrate slush off of the continental shelf, increasing absorption of sunlight due to shrinking ice coverage and reduced gas absorption capacity of a warming ocean.
Here finally is one little mechanism, if we don't rush to build parking lots in Siberia and the Yukon, that might go in favor of stability.