Our best estimate for the global temperature of 2014 puts it slightly above (by 0.01 C) that of the next warmest year (2010) but by much less than the margin of uncertainty (0.05 C). Therefore it is impossible to conclude from our analysis which of 2014, 2010, or 2005 was actually the warmest year.
That may seem like not such a big deal, but it is really. At the moment the big debate in this area is about the "hiatus" - has global warming been stalled for the last fifteen-years-plus, or not?
If you think it hasn't, and you're seeking to convince ordinary folk without advanced knowledge in the area, it is a very powerful thing to be able to say "last year was the warmest on record".
If on the other hand you contend that global warming has been on hold for over a decade, saying "last year was almost exactly as hot as 2005 and 2010" fits exactly with the story you are trying to tell.
It matters, because colossal amounts of CO2 have been emitted during the hiatus period - on the order of a third of all that has ever been emitted by humanity since the Industrial Revolution, in fact. Nobody says that CO2 isn't a greenhouse gas, but it could well be that it isn't nearly as serious a problem as had been suggested.'