I don't think it is a case of either/or.  There are numerous factors at work and I chose to highlight one.  What I found interesting, as a non climate scientist, is the quite drastic effect relatively small changes in average global temperatures can have in particularly regions, and the degree to which even non-anthropogenic climate change has, in the past, led to quite sudden and dramatic changes in Europe in particular.

Petoukhov talks of other correlations being stronger, but the excerpts you quote don't really provide a theory of causation which explains why low ice in the East Arctic should result in colder winters in NW Europe and doesn't exclude the possibility of global warming ->low Arctic sea ice -> reduced thermohaline circulation -> weaker NAD -> colder winters.

In any case, I'm not qualified to debate the finer points of the available evidence and theories. My purpose was to demonstrate that whilst you cannot prove that exceptionally cold winters in NW Europe are caused by global warming, you cannot exclude that possibility either, and there is no reason why slow and gradual global trends cannot lead the sudden and dramatic localised fluctuations.

Index of Frank's Diaries