I guess the answer is yes.

"While these projections were done with one of the world's most sophisticated climate system models, the calculations do not include the feedback effect of the released carbon from the permafrost."

Evidently it is too much to expect, that scientists remember their basic math education and take it into account in climate modeling.  

The only explanation I can think of is that politics must be effecting studies like this.  Climate scientists MUST understand feedback effects and exponential change.

How do they graduate and suceed in academia without that kind of understanding?  Mind boggling.

So how do we fight the extra powerful feedback effect of GHGs like methane and nitrous oxide?  By curtailing their emissions where we can.  From the waste stream.

If 5% of our energy use was provoded by biogas, it would offset the rest of our GHG footprint and halt climate change.  And that would stop tundra, methane hydrate sea floor ice, and glacier and ice cap melting.  All exponential feedback climate changers.

We have to get a handle on the extra powerful GHGs we can control.  Biodigestors powering up tractors,trucks, trains, and grid backup with methane could get us to 5% easily.  And save oil and money.  paying its own way while turning climate disaster around.

Organic fertilizer from the biodigestors would replace ammonia fertilizer, thus curtailing nitrous oxide emissions.  This is a huge GHG effect.  Up to 2/3 the carbon sequestered by crops is negated by the nitrous oxide emitted by the ammonia fertilizer.

Across all chemical ag that has a catastrophic GHG effect.