At present, no one other than GISS claims 2010 is the hottest year ever. The Met Office has announced their intentions to “adjust” their data in order to make 2010 (possibly) #1, but it hasn’t happened yet.
The other half of the story is that the main reason temperatures were recorded high during January-April was because of the record low Arctic Oscillation. The same weather pattern which made much of the Northern Hemisphere very cold, also brought balmy -21C weather to the Canadian Arctic – as opposed to the normal -25C weather.
-21C isn’t “hot” by most people’s definitions.