date: Tue, 03 Mar 1998 10:00:15 -0700
from: Connie Woodhouse <woodhous@ngdc.noaa.gov>
subject: Nature paper
to: Keith Briffa <k.briffa@uea.ac.uk>

Keith, I found your recent Nature paper on the decreasing sensitivity of
tree-growth to temperature in the second half of the 20th century quite
interesting.  I've been working with a collection of tree-ring chronologies
for the Colorado Front Range (you've probably used some of these
chronologies in your analysis) and have noted something similar.  Although
I'm looking at ring widths, and these are more high-elevation than high
latitude, I found that most of the higher elevation species (limber pine,
lodgepole pine, bristlecone pine) have an inconsistent response to climate.
I've been trying to put together a decent regional precipitation
reconstruction, so I just deleted those chronologies from my analysis, and
have been working with ponderosa pine and Douglas fir, the lower elevation
species, which seem to have a stable response to climate.  I know Don
Graybill noted this inconsistent response with high elevation species when
he worked in this area 10 years ago, and he seemed to think the change took
place in the 1930s.  I haven't looked very closely at these chronologies
yet, but this change in response/sensitivity is something I'd like to look
at, especially in light of you and your co-authors' findings which suggests
a possible hemispheric-scale forcing. 

Thanks for a thought-provoking paper!

Connie

Connie Woodhouse
NOAA Paleoclimatology Program
National Geophysical Data Center
325 Broadway St.
Boulder, CO  80303
(303)497-6297

woodhous@ngdc.noaa.gov

