Overall Accuracy
Between 2008 and 2012, the model-based and statistical predictions have had the most accuracy, with an average difference from the observational data of 15%.  However, in recent years the statistically-based predictions have been the most accurate.  The heuristic predictions have been slightly less accurate, on average 17% off from the observations between 2008 and 2012.

The lower accuracy of the heuristic submissions is primarily due to the inaccurate predictions of the climate contrarians, which one Skeptical Science contributor has described as "hubristic," since they are based more on irrational optimism, unwise focus on short-term noise, and hubris than logic or experience.  Ignatius Rigor's heuristic predictions have also not fared well (Figure 1), which are based on the belief that the Arctic Oscillation plays a major role in sea ice extent - a hypothesis which appears not to be borne out by the data thus far.

Climate contrarian bloggers and blog readers (Watts, Goddard, Bastardi, and WUWT readers) averaged a 24% miss with their hubristic sea ice extent predictions, while climate realist bloggers and blog contributors (tamino, Cawley, and Grumbine) averaged just a 10% miss with their statistically-based predictions.  The take-home lesson here is that statistical predictions based on the long-term Arctic sea ice death spiral are clearly more realistic than denial-based optimistic predictions that sea ice will somehow magically recover to previous levels.