G'nut,

I'm not sure the articles really address our local situation for at least a couple of reasons. First, there are problems with the technical accuracy and presentation of the articles (which seems to be the case with many articles these days). The two articles you posted seem written more to make points than to present science, and gloss over much of the relevant data/scientific evaluation. Even if you wholeheartedly embrace the predictions of the writers, you wouldn't want to use the articles in proof of the position.

Second, our local weather is affected more by weather patterns than any overall global warming/cooling trend. The very warm winters we have had here in Tennessee for the past decade or so are not (at least directly) because of global warming. Just as our weather has been noticeably warmer on average, other regions have been cooler.

The bottom line is that the articles don't address concerns directly related to our immediate gardening endeavors. Base zone-pushing on your willingness to compensate for local weather and your ability to deal with losses when they occur.

No one, especially global climatologists, knows your garden like you do. If you're like most gardeners, you probably have at least two or three microclimates in your yard. Those microclimates may be as much as a full zone, or more, different than other surrounding areas.

Here's how I make my decisions. When I'm choosing a tree or a very long lived and expensive perennial, I go for the plants proven hardy down to zone 6. That way, even in an unusually cold winter, I'm probably safe. For other plants, I'm more adventurous and sometimes pick things hardy only down to zone 7a. If I'm planting something in a warm microclimate (up against a brick house, for instance) I may even try a zone 7b or 8a plant. I'm not willing to add insulation, Christmas lights, or other protection to plants, so I don't grow plants, more tender than that, outside. Of course, none of this has anything to do with global warming, cooling, or the price of durian in Brunei.