Tuesday, May 15, 2012


date: Fri, 24 Jun 2005 17:05:14 -0600
from: Raimund Muscheler <raimundatXYZxyzr.edu>
subject: solar activity
to: k.briffaatXYZxyz.ac.uk

<x-rich>Dear Keith,

Caspar Ammann told me that you are coordinator of the discussion about
climate change during the last 1000 years. There are conflicting
results about the changes in solar activity during the last 1000 years
(e.g. Bard et al., 2000, Usoskin et al., 2003) with potentially
important implications for the discussion of the influence of natural
causes on the current climate change. Therefore, we discussed the
radionuclide-based evidence of past changes in solar activity and the
reasons for the conflicting results. We also included new calculations
about past changes in the 14C production rate that we could connect to
the instrumental data.

Caspar said that you might be interested to see the paper (I attached
the title & abstract below).

Best regards



Changes in solar activity during the last 1000 years inferred from
radionuclide records


Identification of the causes of past climate change requires detailed
knowledge of one of the most important natural factors - solar forcing.
Prior to the period of direct solar observations, radionuclide
abundances in natural archives provide the best-known proxies for
changes in solar activity. Here we present two independent
reconstructions of changes in solar activity during the last 1000
years, which are interred from 14C and 10Be records. These records
exhibit a good agreement that allows us to obtain a reliable estimate
of past solar magnetic modulation of the radionuclide production rates.
Differences between 10Be records from Antarctica and Greenland indicate
that climatic changes have influenced the deposition of 10Be during
some periods of the last 1000 years. The radionuclide-based
reconstruction of past changes in solar activity does not always agree
with the sunspot record, which indicates that the coupling between
those proxies is not as close as has been assumed by some authors. The
tree ring 14C record and 10Be from Antarctica indicate that recent
solar activity is high but not exceptional with respect to the last
1000 years.

Raimund Muscheler

National Center for Atmospheric Research

Climate and Global Dynamics Division - Paleoclimatology

1850 Table Mesa Drive

Boulder, CO 80305-3000 USA

tel: 303-497-1399 fax: 303-497-1348

email: raimundatXYZxyzr.edu


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