Calibration of radiocarbon results is needed to account for changes in the atmospheric concentration of carbon-14 over time. These changes were brought about by several factors including, but not limited to, fluctuations in the earths geomagnetic moment, fossil fuel burning, and nuclear testing.

How are radiocarbon years calibrated to obtain calendar years?

The ratio of carbon 14 to carbon 12 in the atmosphere is not constant, which alters the baseline for calibrating dates. To match radiocarbon years to calendar years, researchers have turned to independent timescales based on tree rings, ice cores and uranium-thorium dating.

What is good calibration curve?

For a good calibration curve, at least 5 concentrations are needed. Now, run samples with the analytical instrument, in this case a UV-Vis spectrophotometer, in order to determine the instrumental response needed for the calibration curve.