>I just find it difficult to believe the Antarctic core samples, or
volcanoes,
>or tree rings can show the temperature fluctuations of 1 or 2 degrees and if
>New Jersey received 8 or 28 inches of snow in a five year window thousands
>of years ago. This is the degree (no pun intended) of change everyone's
>talking about, right? and blaming global warming. I certainly agree we
should
>lower pollutants released whether in air, ground or water, but I'm just
still
>suspicious of impending doom for lack of evidence.
>
Well, some of the evidence is somewhat controversial. I don't think that the
scientists are trying to pinpoint the amount of snowfall or a 1 degree change
in temperature, but more general trends. The ice cores, for example, have
bubbles of ancient air in them, but it isn't at all certain that the air is
an accurate reflection of the atmosphere at the time it was frozen, since ice
is known to emit various gases upon exposure to sunlight. Tree rings provide
a good record, and I have a personal interest in them. I think I posted
something about this awhile back. Anyway, you can tell fairly accurately
whether the climate was favorable for tree growth on a year to year basis
with tree rings. A favorable climate usually means proper temperature and
adequate moisture. They can compare recent tree ring data with available
weather data and find out how much the tree will grow under a given weather
pattern. Then, assuming that the tree responded the same way 500 years ago,
you can figure out what the climate was back then based on the tree rings.
The trouble is that climate as revealed by the tree rings of a particular
tree only tell what the climate was in the immediate vicinity of that tree,
so samples from many trees around the world are required. There is a project
under way right now to collect and store the data from tree rings from around
the world to get a more accurat picture of the world climate.
There's an interesting point I learned about the Bristlecone Pine, a very
long lived tree species in the Western US. In one particular range of these
trees, they grow up to the snow line, but there are dead trees above the snow
line. What does this say? It says that the climate there was at some point
warmer and wet enough to allow them to grow up there. Then, you can take core
samples from the dead trees, and line them up next to samples from the live
trees nearby, and they will match at some point. The point in time where the
dead tree died is where the climate had changed enough to not support it any
more.
There are also efforts to get samples from ancient timbers that have been
preserved somehow, either in caves or under deep water and take samples from
them. I find this whole subject area very interesting.....
--
Be Seeing You.
Dirk Wright
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