People constantly get polar amplification wrong. The most obvious mistake is to assume it applies equally at both poles. It doesn’t in both models and observations: there is far more warming in the Arctic (at present, and expected in the future. This picture is somewhat complicated if you look back to, say, the last glacial, where climate change was amplified at both poles; but thats because it was for long timescales, hence the stabalising effect of the Southern Ocean doesn’t apply (e.g. this RC post)).
But they also get the mechanisms wrong, too.
Hence, as OM points out in Natures blog, the apparently bizarre trumpeting (and not only by the septics) of a new result showing that warming in the mid-trop is contributing to Arctic warming as supposedly proof that its not anthropogenic. As OM puts it there is an idea that the ice-albedo effect and anthopogenic warming are effectively synonymous, and that if warming isn’t due to the feedback but to increased atmospheric transfer of heat then it is more “natural” and less “man-made”. But in fact increased mid-trop forcing is perfectly consistent with GW (e.g. Alexeev et al) and is arguably a signal of it. Which is one reason we were quite pleased to find enhanced trop warming around Antarctica… it suggested links to the wider world rather than just local effects.
I never really worked out exactly how much Arctic amplification was supposed to come from this or from that, and I’m not sure if anyone else has. But the (sea)ice-albedo feedback (I think the seasonal snow cover on land may be more important) is such a nice easy idea that everyone loves it.
[Update: thanks to H for noticing this over at RC
I read the Nature paper. It is an intersesting paper and I agree with you that if the authors had analyzed the CMIP3 output, it would be much better. I also don’t think it is right to say that in the CGCM models the ice (snow) albedo feedback is the main mechanism for polar amplification. We  have recently published a paper and theoretically proved the feedback from heat transport greatly influence the vertical and meridional structure of global warming. It is important to point out the heat transport feedback does not have to warm the atmosphere only, it also can cause a larger surface warming by the concurrent other thermal-dynamic feedbacks.
 Ming Cai & Jianhua Lu (2007),
Dynamical greenhouse-plus feedback and polar warming amplification. Part II: meridional and vertical asymmetries of the global warming
Climate Dynamics Vol 29:375-391
doi 10.1007/s00382-007-0238-9 -W]