I don't think you are reading that correctly. If you look at the dip after the spike then all of the spike has already disappeared. Also, as you move to the right it takes an ever larger difference to move the number. Think of it this way, after 10 samples it takes a number 11 above the average to increase the average by one, but after 20 samples it takes a number 21 above the average to increase the average by 1.
So, while the 1998 graph and the 2012 graph look close at the end the actually daily values in 2012 needed to be significantly higher than 1998 values to create that much separation when they so recently crossed each other.
Infact it's actually 1976 that had the most comparable march from the sample given. However, because those years where chosen because their jan - march average was so far above the average it does not really show how abnormal 2012 was. Consider, where the average is and how many colder years it takes to average out to that.
So, while the 1998 graph and the 2012 graph look close at the end the actually daily values in 2012 needed to be significantly higher than 1998 values to create that much separation when they so recently crossed each other.
Infact it's actually 1976 that had the most comparable march from the sample given. However, because those years where chosen because their jan - march average was so far above the average it does not really show how abnormal 2012 was. Consider, where the average is and how many colder years it takes to average out to that.