Yeah, this absolutely crucial piece of information is missing from most articles like this one, a journalistic failure I find incomprehensible.

Anyways, the Woods Hole Research center claims that boreal forest fires are not included in current climate models, and are likely to exacerbate the problem: http://whrc.org/wp-content/uploads/2018/11/PB_wildfires.pdf

I think the models did consider this. And in such models, this is one of the "tipping points" (along with sea ice / glacier ice melting) beyond which it becomes much more difficult to reverse the process.