Monday, December 5, 2011

0912633188.txt

From: Bob Keeland <Bob_Keeland@USGS.GOV>
To: ITRDBFOR@LISTSERV.ARIZONA.EDU
Subject: Re: verification and uniformitarianism
Date: Wed, 2 Dec 1998 16:13:08 -0700
Reply-to: grissino@VALDOSTA.EDU

Frank is correct in that we need to define 'abrupt climatic change' or
even just 'climate change.'

Using Jim's Schulman Grove example suppose that the area supported a
stand of bristlecone pine 9,000 or more years ago, hence the scattered
remnants. Either a major catastrophic event or a fluctuation in climate
(call it climate change if you want) resulted in conditions that killed
the mature trees and eliminated any further recruitment for up to 1,000
years. This site may be near the limits of recruitment and with a major
(or minor perhaps) change in climate it could easily be beyond the
limits of recruitment. About 8,000 years ago climate again became
favorable for bristlecone pine recruitment and a new stand(s) developed
and have existed ever since. Some or most of the material remaining
from the original stand may be buried down in the valley, or the
original stand may have been small or sparse. The amount of time
between the loss of the original stand and the beginning of the new
stand would depend on the period of unfavorable weather and the amount
of time needed for bristlecone pine to re-invade the area. I am out on
a limb here, so to speak, as I an somewhat ignorant of prehistoric
climate patterns for the area and of bristlecone pine ecology, but this
seems like a relatively reasonable scenario.

I guess that my point is that climate continues to fluctuate within
broad bounds. Everything that we are now calling 'climate change' is
well within the bounds observed within the prehistoric record of climate
fluctuations. Do we call any variation 'climate change' or should we
limit the term climate change for anything considered to be caused by
humans? To my mind it is not so much what we call it, but rather that
we keep a clear idea of what we actually talking about.

Bob Keeland
USGS, National Wetlands Research Center
Lafayette, LA
bob_keeland@usgs.gov

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