Re: REF: zone maps
My situation here is rather like Linda's--what happens here right on the
border between 6b and 7a on the old maps is upgraded to a full-blown 7 in the
most recent USDA maps. I did an Internet search and can't find the new map.
The revision was published only within the last one, two or three years, I
think.....reflected global warming. Does anyone have that URL?
Like Linda, we haven't seen really cold winters in a long time. This year our
coldest has been 8.8 degrees ABOVE zero--I hate to think what the summer will
One thing about global warming (regardless how one wants to argue the cause)
is that with the gradient of change as steep as it is right now, the whole
world climate and oceanic circulation is disturbed, confused and causing all
sorts of contridictions in what has "always" been so.
But it hasn't always been stable at all! The studies that have been done on
pond muds in both the western US and in Labrador show pollens from plants that
are "zone" indicators. The variations over the past 100k years or more is
astounding. Climates march back and forth for a whole variety of reasons--the
amount of dust in space between us and the sun, the amount of volcanic
micro-ash in the air, the amount of carbon particles from massive range or
forest fires in the air, the instability of solar activity--which varies--and
the geometry of the sun/earth/declination patterns. The earth moves around
the sun in something that isn't quite a circle, and the closer we are to the
sun, all things else being equal, the warmer. The farther away, the cooler,
by the distance squared rule.
Then, to really complicate things, during the year, the part of our revolution
around the sun that brings us closest varies according to which hemisphere is
in summer at that time. Right now, the southern hemisphere is getting a
hotter summer, colder winter effect because of the tilt. 12 or 13,000 years
from now, the northern hemisphere will be in that position.
All things AREN'T equal, though, and the ice core samples from Greenland give
a record of climate with all sorts of lateral data, such as methane
percentages, CO-two percentages and so on in the air at any one time. The
range of variation is rather substantial.
Another thing that is wildly climate-changing is a cycle of off and on for the
Gulf Stream. Certain kinds of events tend to shut off the system of cold flow
deep, warm flow shallow in the No. Atlantic basin. The cyclic system is
slowly shutting down now according to some indications--which will radically
change climates both in N. America and Europe. Not in our lifetime,
perhaps--but it looks like that is part of the variation.
The point being--zone maps are true for a time, more or less, ignoring
microclimate effects--but not over long periods. Zones change. Right now
they are changing rather rapidly.
Neil Mogensen z whatever, NC mountains
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