I suspect that many who follow this thread do not realize that anthropogenic aerosols have been both more effective at global cooling than previously projected; but as the linked reference shows anthropogenic aerosols have been more effective still at masking/damping Arctic Amplification even than it has been at masking/damping the increase in mean global surface temperature. Thus as aerosols are cleaned-up (projected to occur very rapidly in China, which is only of the largest sources of aerosols) the Arctic will warm faster than previously estimated. This means that looking at the old trend lines many not be a good indication of how much Arctic sea ice loss will occur in the coming couple of decades (certainly a seasonally ice free Arctic in 2017 is not in the cards at this time, but I think it could happen by 2030 to 2035):
Najafi, M.R., et al. (2015) Attribution of Arctic temperature change to greenhouse-gas and aerosol influences, Nature Climate Change, doi:10.1038/nclimate2524
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2524.htmlAbstract: "The Arctic has warmed significantly more than global mean surface air temperature over recent decades, as expected from amplification mechanisms. Previous studies have attributed the observed Arctic warming to the combined effect of greenhouse gases and other anthropogenic influences. However, given the sensitivity of the Arctic to external forcing and the intense interest in the effects of aerosols on its climate, it is important to examine and quantify the effects of individual groups of anthropogenic forcing agents. Here we quantify the separate contributions to observed Arctic land temperature change from greenhouse gases, other anthropogenic forcing agents (which are dominated by aerosols) and natural forcing agents. We show that although increases in greenhouse-gas concentrations have driven the observed warming over the past century, approximately 60% of the greenhouse-gas-induced warming has been offset by the combined response to other anthropogenic forcings, which is substantially greater than the fraction of global greenhouse-gas-induced warming that has been offset by these forcings. The climate models considered on average simulate the amplitude of response to anthropogenic forcings well, increasing confidence in their projections of profound future Arctic climate change."
See also (both extract and image):
http://www.carbonbrief.org/blog/2015/02/aerosols-dampen-pace-of-arctic-warming-for-now-say-scientists/Extract: "And the results suggest the cooling effect from aerosols is much larger in the Arctic than elsewhere in the world, Najafi adds. A separate study finds aerosols were responsible for offsetting around five per cent of global greenhouse gas warming between 1901 and 2010, and around 27 per cent for the shorter period of 1951 to 2010.