Two things stand out about the current USHCN data tampering graph. The most obvious is the huge amount of tampering going on in 2014, but almost as bizarre is the exponential increase in tampering since about the year 1998.
There is no rational reason for either of these – so here is my guess. Obama wants credit for healing the climate. He has been engaging in every imaginable form of BS to get an international agreement through this year or next, and after he gets the agreement he will tell NOAA to stop tampering – and will then take credit for the drop in temperature.