Kristian posted a WUWT comment here, saying that GISS land mask had failed, and showing (from here) this plot:
It shows trends (despite y-axis label) of land-masked GISS vs OIv2 SST, which GISS used at the time. The divergence near the poles is attributed to GISS "deleting data". Now I should say that this plot does not seem to have been cross-posted at WUWT. But it expresses Bob's complaint at WUWT about deleting data, and is referred to most months at WUWT (see pingback list) in Bob's updates, most recently Nov 2015 here. The boiler-plate complaint is
Unlike the UK Met Office and NCEI products, GISS masks sea surface temperature data at the poles, anywhere seasonal sea ice has existed, and they extend land surface temperature data out over the oceans in those locations, regardless of whether or not sea surface temperature observations for the polar oceans are available that month. Refer to the discussions here and here.
So what is happening? Note that the plot goes from 77.5S to 82.5N. You might reflect on what SST at the frozen ends might mean. In the 2010 WUWT post, titled "GISS Deletes Arctic And Southern Ocean Sea Surface Temperature Data", I tried to point it out here and here. The SST products OI V2 and ERSST, used by GISS then and now, adopted the somewhat annoying custom of entering the SST under sea ice as -1.8°C. They did this right up to the North Pole. But the N Pole does not have a climate at a steady -1.8°C. GISS treats this -1.8 as NA data and uses alternative, land-based measure. It's true that the extrapolation required can be over long distances. But there is a basis for it - using -1.8 for climate has none, and is clearly wrong.
So is GISS "deleting data"? Of course not. No-one actually measured -1.8°C there. It is the standard freezing point of sea water. I guess that is data in a way, but it isn't SST data measured for the Arctic Sea.
It's worth checking the origin of Bob's plots. He partly explains, saying they came from KNMI. And yes, if you go to this page, and look down to SST and "1982-now: 1/4° NOAA OI v2 SST", you'll see an interactive display inviting you to enter latitude bands. If you ask for, say, 85N to 90N, it will, by default, return an anomaly time series of band averages. Surprisingly, this isn't quite zero - apparently not all the entries are exactly -1.8. But it is close, and has no trend.
If you click on the "authoritative data", it takes you to here, with this animated GIF:
The dark blue is -1.8°C, and you'll see that both high Arctic and deep Antarctic are -1.8°C year round. Now KNMI provides a mechanical process here. It averages whatever data set you request. If it is all -1.8, that's the average it returns. St that is where the top plot comes from. Bob originally requested and plotted the latitude bands. But of course, where it is returning -1.8, there is no trend. There can't be. So the OI v2 trend goes to zero at the ends, which is nonsense. On this basis, the arctic areas just can't warm. But they do, as GISS shows.