Here are the results for the Moyhu NCEP/NCAR reanalysis index for August. It looked for a while to be a record breaking month, with steady warmth. But then there was a sudden late cool spell, apparently mostly Antarctica, and then an equally sudden recovery to warmth. The end result was 0.306°C, a big rise from July's 0.164. That is just slightly cooler (in this record) than May 2014 at 0.315°C. But it is the warmest for 2015 so far.
It makes a slight difference month-month what anomaly base period is used, and so the Moyhu table gives results also on the 1951-80 base (for GISS) and 1961-90 (NOAA Mlost). So the comparable GISS-base number would be 0.87°C. But as mentioned in earlier posts, the NCEP index, being air temperature, has been running rather cool relative to the land/ocean indices which using the warm current SST. So I would not be surprised if GISS were even higher - maybe even 0.9°C. The record GISS anomaly is Jan 2007 at 0.96°C.
ps This post is a little later than usual. The volatility meant that I wanted to go right to the end of month, and the last day of NCEP/NCAR was posted a little late at NOAA.