EBarnacle-
You have hit upon one of the most important positive feedbacks of all!
Yes, yes, yes, there should be a lot more discussion of this:

The Earth warms slightly...
So, polar sea ice shrinks a little bit...
Since water has a much lower emissivity than ice...
So, the exposed ocean absorbs more thermal IR...
So, the Earth warms a little...
so, polar sea ice shrinks a little...
...
...
...


Be very worried. This is a runaway process.


Sort of like the Mewthane bomb.
The Earth warms a little...
So, some permafrost thaws...
This releases just a little bit of methane...
Methane is a much more powerful greenhouse gas than carbon dioxide (right BB?)...
So, the Earth warms a bit more...
So, some permafrost thaws...
...
...
...


Get it?