[aerohead]

Sure,they're working with numerical models,but since 1995 they pretty much ruled out natural variability and have found a correlation which does incriminate anthropogenic forcing,with seasonal preference,especially in the Northern Hemisphere.
The trend began in 1950,when CO2 really took off.
It was only when they factored in Sulfate aerosol cooling that observations began to fit projections.
CO2 insn't going down,so there might be an expectation to see the trend continue.It's their job to throw a caution flag on the field if they see something fishy.
We'll have to just wait and see how it plays out.
Re:'Towards the Detection and Attribution of an Anthropogenic Effect on Climate,' B.D.Santer etal.,PCMDI Report No. 21,Lawrence Livermore National Lab.,1995,from SCIENCE,VOL.268,16 JUN 1995,p.1568.