Scientists must assume how much carbon-14 was in the organism when it died.Complicating matters is the fact that Earth’s carbon-14 concentrations change drastically based on various factors.Contamination and repeatability are also factors that have to be considered with carbon dating.A tiny amount of carbon contamination will greatly skew test results, so sample preparation is critical.Modern effects such as fossil fuel burning and nuclear testing have also changed atmospheric carbon-14 levels and in turn change the “starting point” for a radiocarbon test.All in all, setting the parameters of the carbon-14 test is more of an art than a science.Question: "Is carbon dating a reliable method for determining the age of things?" Answer: Carbon dating, or radiocarbon dating, like any other laboratory testing technique, can be extremely reliable, so long as all of the variables involved are controlled and understood.
This is perhaps the greatest point of potential error, as assumptions about dating can lead to circular reasoning, or choosing confirming results, rather than accepting a “wrong” date.
In short, carbon dating is as useful as any other technique, so long as it’s done properly and the results are objectively interpreted.
It is not, however, an inherently error-free or black-and-white method for dating objects.
So even brand-new samples contain incredibly tiny quantities of radiocarbon.
Eventually, the amount of carbon-14 remaining is so small that it’s all but undetectable.