Carbon dating reliability
The answer to the problem of fluctuating amounts of this important isotope is calibration.
While an uncalibrated reading may be off by a factor of 10%-20%, calibration severely reduces that value.
This is because radiocarbon dating gives the date when the tree ceased its intake of Carbon-14—not when it was being used for weapons and other instruments!
Standard calibration curves are now used for more accurate readings.
These curves indicate the changes in Carbon-14 throughout the years and modifies the end result of the tests to reflect that.
This method, which received widespread attention in connection with the Dead Sea Scrolls, relies on the fact that all living things take in carbon, some of which is very slightly radioactive. To hear some people tell it, scientists have nearly absolute confidence in the dating methods they use.
When their dating methods say that something lived 30,000 years ago, they sound certain.