evidence: Since the beginning of satellite observations in 1979, Arctic sea ice coverage and volume in summer has decreased by approximately 50% and 70%, respectively, making it one of the most alarming signs of climate change1,2,3,4,5,6,7. To cope with the impacts of the shrinking area of sea ice, such as more freshwater storage, more frequent extreme weather events in the mid-latitudes, and changes to global shipping and trade passages8,9,10,11, adaptation and mitigation planning are based on credible projections of Arctic sea ice. Climate models collected in model inter-comparisons play a central role in formulating various management strategies. These strategies are based on probabilistic predictions about the outcomes of interest under different forcing scenarios, which are provided by simulations from carefully constructed model ensembles. However, models feature diverging projections of Arctic sea ice4,12,13,14,15,16,17,18, mainly because of model differences, such as different model responses to the same external forcing19. Some models might be biased in the same way when sharing portions of code, input datasets, or even the expertise of those developing the model, which could cause the multi-model mean to be biased low or high. [...] Mahlstein, I. & Knutti, R. September Arctic sea ice predicted to disappear near 2 °C global warming above present. J. Geophys. Res.117, D06104 (2012).