Alternatively, one can use the current internationally-ratified marine calibration curve Marine04 (Fig.
1) with a known value of regional offset from the global marine model age for that sample, defined as R and R of a location are usually assumed constant through time.
However, this assumption is not exactly true, so that radiocarbon ages become progressively too young with age; 5000 14C years is about 5700 calendar years, 11,000 14C years is about 13,000 calendar years, 20,000 14C years is almost 24,000 calendar years, and so on.
A correction is possible based upon dating of tree-rings of known age and from paired radiocarbon and uranium-series dates of corals.
The current internationally-ratified calibration curve for terrestrial samples (e.g., woods, charcoals and macro-fossils) from the Northern Hemisphere is Int Cal04, which covers the past 26,000 calendar years (cal yr) (Fig. This curve is based on dendrochronologically-dated tree rings for the period 0-12,400 cal yr before present (BP, with 0 BP being AD 1950).
For the remaining period 12,400-26,000 cal yr BP, the curve is derived from independently dated marine samples such as foraminifera and corals.
Plants take up 14C during photosynthesis, and animals acquire 14C from eating plants.
An assumption of 14C dating is that the amount of 14C in the atmosphere has remained constant.
During this time the C level intermediate between these two reservoirs.
To access our radiocarbon calibration program, click on the 'Radiocarbon Calibration Program' button above, or here.
Arguably, few research topics engage so many different fields of science and have such a profound impact on our understanding of Earth and Solar science as the history of C in the Earth's atmosphere and the surface and deep oceans.
This dating method is usually called bomb-pulse dating (for the interval from 1950 onwards) to differentiate from traditional radiocarbon dating (for the period from 1950 backwards). Additional calibration programs can be found on the Radiocarbon journal website at
Four zonal data sets of tropospheric bomb C ages is usually undertaken using a computer program. Examples of radiocarbon calibration for the traditional radiocarbon dating and the bomb-pulse dating are shown in Figs.