Thanks ... though I wish the author had actually cited the studies instead of saying "medical studies have shown" or vaguely referencing "various scientific studies."
There is also an existing thread on seed suppliers here:
http://www.sufficientself.com/forum/viewtopic.php?id=12067
Not too many are listed but there are a few.
No doubt many of us feel that it is "close" or "near" but our definition of those terms may not be the same. Perhaps a more meaningful way to ask is for an "order of magnitude" estimate. Days? Weeks? Months? Years? Decades? Centuries?
I feel that a truly life-altering change is several years away.
The surface of the earth is approximately 500,000,000 square km. What percentage of that do you estimate is affected by bringing down air that is 1-2C warmer than the surface, for a few hours of the early morning, on some days?
They're bringing warmer air down during times of an inversion, just as wind machines do for orchards and vineyards during spring freezes, to prevent frost damage. They are "warming a small piece of ground," not "warming the earth."