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Deep permafrost thawing has been observed for several years now, and is a major threat to buildings in Alaska.
The area is already producing large amounts of GHGs, primarily CO2 and methane, because of the activation of organic decomposition, especially in the soil. This change has already been detected. In addition, oceanic warming is allowing an increased release of methane from seabed methane clathrate ice slurries -- world-wide.
I think we've been beyond the "tipping point" since about 1990. There has also been a recent major influx of "cosmic dust" since the late 1990s which I strongly suspect plays a big part in climate on all the planets. But that's just my personal wild hair.
If we're lucky, the changes will produce a "climate flip-flop" to a new minor ice age in the next ten years.
If we're not so lucky, the weather will get hotter each year for about fifty years, and the climate flip-flop will be more intense, and lead to a major ice age around mid-century.
If we're shit-out-of-luck, we will defeat the state-change mechanism that causes the "flip-flop", and a runaway greenhouse will be established. Within 2000 years, the Earth would be a sterilized autoclave; in 100,000, the Earth would be a twin of Venus.
But we're not going to do anything until we realize that we're up the creek without a paddle. That will probably take a few more years, though recent weather disasters -- a glut of hurricanes and typhoons, July snow in Europe, unusually strong Eurogales, partial monsoon failure in Asia, etc. -- may compel this awareness sooner than later.
--bkl
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