But the changes from emissions will require some extra adjustment, even in the study’s best-case-scenario emissions projection.“If emissions are rapidly reduced, then the decrease in the fraction of radiocarbon in the atmosphere will be equivalent to only about a hundred years of radioactive decay,” said Graven.The only major fluctuation we know of occurred when we began detonating nuclear weapons in the open air, back in the mid-20th Century.
The amount of carbon-14 in living plants and animals matches the amount in the atmosphere, but when plants and animals die, they no longer absorb carbon-14.
Because radiocarbon has a known rate of decay, scientists can determine about how long it has been since the plant or animal was alive.
“There will be some ambiguities about whether it’s 300 years old or relatively recent.
We’re going to need more information.” Scientists could begin seeing the effects on radiocarbon as soon as 2020, when the ratio is expected to drop below pre-industrial levels, according to Graven.
With a half-life of just over 5,000 years, any Carbon-14 atoms that were created in stars, billions of years ago, have long since decayed away into nitrogen atoms.