The point was that you don't know what data they dropped by shifting the data 15 years forward, and that it only takes a few such "outliers" to shift the mean i

The point was that you don't know what data they dropped by shifting the data 15 years forward, and that it only takes a few such "outliers" to shift the mean in an otherwise flat dataset. Moreover, you wouldn't know how flat the trend in the data actually is from the article itself. For Raleigh (new zone high 8a, almost 8b) there are three winters in the low end of the "previous" zone of 7b in the last 10 years. For St Louis (new zone 7a) there were two winters in zone 6b and one in 5b (!) in the time since 2013. There were an equal number of winters in the "old zone" of 6b and the "new zone" of 6a in the dataset shown. Even calling that an outlier is stretching the definition of the term! And I didn't cherry-pick these examples...these were the ones NPR chose to highlight. This isn't "pedantic". It's a basic understanding of statistics and the methods being applied here.