Tuesday, December 8, 2009
Atmospheric Carbon-14 Ratios
Carbon-14 has a short half life, thus it is not found in ancient fossil fuels. Burning these fuels then decreases the 14C/12C ratio in the atmosphere. This is a measurement of 14C levels from 1820 up until about 1950. Nuclear bomb tests in the late-40s and 50s put large amounts of 14C into the atmosphere, so records after that date cannot be used, Specifically, tree ring data from after 1960 is unreliable because of the nuclear testing, so it is not used in climate modeling: