We've known about this for decades. An example: heating causes permafrost to melt releasing CO2 and methane, which cause more heat to be trapped, which melts more permafrost, which releases more green house gasses, etc.
Positive feedback loops tend to be very unstable, and can lead to runaway situations.
Worse, when that influx of arctic water shuts down the North Atlantic current and others that cycle heat and cold throughout the world. That will be very bad for quite a lot of us.
People are really bad at conceptualizing exponential change from feedback. Our brains expect incremental change. I think that's one of the reasons people can't know accept what is happening.
"I know things are changing, but it's only a bit each day, and it can go like that for years and it won't be that bad."