July 1936 now hottest US month again!

The latest story on all the global warming denier blogs is that July 1936 is the hottest month in the US again. July 2012 was the hottest month in the US for a while, but the figures have apparently, according to wattsupwiththat, been "adjusted", "as if by magic".

Watts goes on to say:

This isn’t just some issue with gridding, or anomalies, or method, it is about NOAA not being able to present historical climate information of the United States accurately. In one report they give one number, and in another they give a different one with no explanation to the public as to why.

Thus proving himself a clown, because if you look at the page Watts got his graph from (NOAA Climate at a Glance), it states very clearly:

NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. 

And it doesn't take much research to find that this is an issue with gridding, that NOAA have explained to the public why it happened, and that Watts is talking out of his bottom when he claims it happened "as if by magic".

The switch to the GHCN-Daily-based dataset has little effect on the average national temperature trend or on relative rankings for individual years. This is because the new dataset is based on gridded anomalies produced using the same set of algorithms and corrections that are applied in the production of the USHCN v2.5 dataset. However, although both the USHCN v2.5 and the new gridded dataset yield comparable trends, the finder resolution dataset more explicitly accounts for variations in topography (e.g., mountainous areas). Therefore, the baseline temperature, to which the national temperature anomaly is applied, is lower (cooler) in nClimDiv than in the USHCN v2.5. This new baseline affects anomalies for all years equally, and thus does not alter our understanding of trends.

NOAA National Overview - January 2014 New CONUS Temperature Dataset

1936 is now 0.03 degree hotter than 2012, where previously 2012 was 0.2 degree hotter than 1936.

The reason this is so significant for global warming deniers is they like to use the fact that the US was warmer in the 1930s as an excuse to dismiss the reality of global warming, just as they like to use the claim that the world was warmer in the Medieval Warm Period.

It looks from the graph above that the US has been warming over recent years, so the deniers may not have long to enjoy the renewed status of 1936 as the warmest year, but let them relish 0.03 of a degree for as long as it lasts.