"Radiocarbon years" refers to the age of an object or sample, but it is specifically based on the amount of radiocarbon present in the object. It is used by scientists to estimate how long ago something lived or died. Full definition
Around 14,000 years ago (about 13,000 radiocarbon years ago), there was a rapid global warming and moistening of climates, perhaps occurring within the space of only a few years or decades. (realclimate.org)
(All dates in this story are in calibrated radiocarbon years.) (sciencemag.org)
The use of complementary dating techniques described in § 2 along with the systematic comparison of clone - size distributions between all post-fire lichen - tundra sites (figure 7c, d) helped to discriminate individual fires, at least back to the last 1000 years and also fires older than 1000 radiocarbon years typically recorded in all the woodlands and krummholz of the study area. (rstb.royalsocietypublishing.org)