Tamino has quite correctly taken this apart. This is his version of the GWPF graph:
As he points out, the claim of no warming is dependent on the dip in April/May 2010. Without it, there is warming, pretty much as expected.
So I checked the BEST data.txt to see why these month data had such large error bars, and were so out of line. It turns out that all the data they have for those months is from 47 Antarctic stations. By contrast, in March 2010 they have 14488 stations.
How this could have happened, I don't know. Anyway, a list of those 47 stations below the jump.
|MCMURDO SOUND NAF||-77.8734|
|DOME C II||-75.1210|
|GEORG VON NEUMAYER, FRG ANT..||-70.6608|
|ZHONGSHAN WX OFFICECI||-69.3670|
|LAW DOME SUMMIT||-66.7330|
|DUMONT D'URVILLE, FRANCE ANT.||-66.6670|
|B. A. VICECOMODORO MARAMBIO||-64.2330|
|ISLAS ORCADAS B.N.||-60.7360|
|GENERAL SAN MARTIN B.E.||-68.1300|
|Larsen Ice Shelf||-66.9000|
|TENIENTE JUBANY E. C., ARG.||-62.2000|
|GRYTVIKEN S. GEORGIA IS.||-54.2700|