I wouldn't exactly call it a cooling trend. Look closely at this graph which comes from the same website:
2005 was in fact one of two hottest years on record, the other one was 1998. True, the warming trend that we saw in the 90's has come to a halt, but who knows for how long and it's certainly not a cooling trend yet. We'll know more in a few years. Given how weak the sun's radiation is right now (solar cycle 24 is barely coming to life), I'm not at all surprised that the warming has taken a pause.