  Using new calculations of 10Be production in the Earths atmosphere which are
based on direct measurements of the 11-year solar modulation effects on
galactic cosmic rays and spacecraft measurements of the cosmic ray energy
spectrum, we have calculated the yearly average production of 10Be in the
Earths atmosphere by galactic and solar cosmic rays since 1939. During the last
six 11-year cycles the average amplitude of these production changes is 36%.
These predictions are compared with measurements of 10Be concentration in polar
ice cores in both the Northern and Southern hemisphere over the same time
period. We find a large scatter between the predicted and measured yearly
average data sets and a low cross correlation ~0.30. Also the normalized
regression line slope between 10Be production changes and 10Be concentration
changes is found to be only 0.4-0.6; much less than the value of 1.0 expected
for a simple proportionality between these quantities, as is typically used for
historical projections of the relationship between 10Be concentration and solar
activity. The distribution of yearly averages in the 10Be concentration level
in the data from the Dye-3 ice core in Greenland for the time period 1939-1985,
contains a "spike" of high concentration one year averages which is not seen in
the production calculations. These and other features suggest that galactic
cosmic ray intensity changes which affect the production of 10Be in the Earths
atmosphere are not the sole source of the 10Be concentration changes and
confirm the importance of other effects, for example local and regional
climatic effects, which could be of the same magnitude as the 10Be production
changes.
