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abrupt transition to higher temperatures. These
findings sug-
gest an
“
abrupt climate change-severe fire and erosion hy-
pothesis
important to pay close attention to what we are currently
doing to the climate that might trigger an ACCE.
fires and erosion occurred in
some locations in the past as a result of the stresses put on
vegetation and slopes by ACCEs.
The entire Coburn Lake and Pyramid Lake records were
also compared with high-resolution temperature and precip-
itation records from Greenland [NSIDC and WDC-A, 1997].
These comparisons provided evidence that the 8200 and
5200 year ACCEs occurred in the northern Sierra Nevada.
The largest charcoal peaks from Coburn Lake were deposited
as severe droughts were beginning in the northern Sierra
Nevada and as severe droughts were ending in Greenland.
In addition, five of the seven largest charcoal peaks from
Coburn Lake were coincident with peak low, but rising,
temperatures in central Greenland.
These findings suggest that temperatures were generally
hot or rising in the Northern Hemisphere as severe droughts
were beginning in the Sierra Nevada and ending in Green-
land. The bidirectional synchronicity of these events sug-
gests a hypothesis that abrupt, large-scale shifts in the
general locations of the Earth
”
that states that severe
rst pre-
sented in May 2005 in Flagstaff Arizona. Thanks to those indivi-
duals who have reviewed versions of this paper since then,
including Michael Barbour, Havunur Rashid, and Jennifer Richards;
those students who helped me process and count charcoal; the
Geological Society of America and the University of California,
Davis for funding; Scott Mensing et al. and Christopher Carcaillet et
al. and NSIDC and NDCP for generously sharing their data; and a
special thanks to Tom Brown at the Livermore CAM Laboratory for
his generous radiocarbon dating of my sediments.
Acknowledgments. Results from Coburn Lake were
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