Ron

By 1966, the nuclear testing had raised, temporarily, the C-14 in the atmosphere
to 2X grater than normal.

But the standard is PDB (Pee Dee Belemenite) so that except for Libby's first
experimental work, no one has used the air as a standard.  And of course with
our greenhouse gas problem, the air would be still more of a problem.

Yes, the idea of picking 1950 was to standarize the whole issue.

But increasingly younger researchers don'g understand/don't like using 1950, and
don't understand why we can't use 2000.  As a previous rep\sondent noted,
changing to 2000 will confuse things, but I suppose no more than the people who
use "calibrated' dates now, who don't tell you which one of several different
calibration procedures they might have utilized, so you haven't a clue what
their 'calibrated' date means.

As I note, there was a move afoot to change the 'standard' from 1950 to 2000,
but I don't know if it was accepted or not.

dave browman


> Dave,
>
> I thought "1950" was selected because prior to that time atomic bomb testing
> had not contaminated the atmosphere like it is now. The date is used in
> calibration to screen out that contamination point in time. Perhaps you are
> too young to remember, but the United States and Russia were triggering off
> hundreds of nuclear blasts (above and below ground) and underground triggers
> during the Cold War. The degree of atmospheric carbon affected by all that
> activity has been dramaic. Would you add the 50 years of contamination simply
> to have a convenient calibration date?
>
> Ron May
> Legacy 106, Inc.