The big difference compared to a tipping point scenario is the prolonged presence of winter sea ice. (bitsofscience.org)
In fact, there has been a slight gain in winter sea ice since 1979: about 0.2 million square miles. (realitydrop.org)
It is also noteworthy that winter sea ice extent in individual years is not well correlated with subsequent ice melts and the resulting summer minimum. (deepclimate.org)