Editing Carbon-14 (section)

===Formation during nuclear tests===
[[File:Radiocarbon bomb spike.svg|thumb|300px|right|Atmospheric {{sup|14}}C, [[New Zealand]]<ref>{{cite journal | vauthors = Manning MR, Melhuish WH|url=http://cdiac.esd.ornl.gov/trends/co2/welling.html |title=Atmospheric δ{{sup|14}}C record from Wellington |access-date=2007-06-11 |journal=Trends: A Compendium of Data on Global Change. | publisher = Carbon Dioxide Information Analysis Center |year=1994 |url-status=dead |archive-url=https://web.archive.org/web/20140201222225/http://cdiac.esd.ornl.gov/trends/co2/welling.html |archive-date=2014-02-01 }}</ref> and [[Austria]].<ref>{{cite journal| url=http://cdiac.esd.ornl.gov/trends/co2/cent-verm.html| vauthors = Levin I, Kromer B, Schoch-Fischer H, Bruns M, Münnich M, Berdau D, Vogel JW, Münnich KO | title=δ{{sup|14}}C record from Vermunt| journal=Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center| year=1994 | url-status=dead| archive-url=https://web.archive.org/web/20080923105819/http://cdiac.esd.ornl.gov/trends/co2/cent-verm.html| archive-date=2008-09-23| access-date=2009-03-25}}</ref> The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere. Atmospheric nuclear tests almost doubled the {{sup|14}}C concentration of the Northern Hemisphere.<ref>{{cite web | url=http://www1.phys.uu.nl/ams/Radiocarbon.htm | publisher=University of Utrecht | title=Radiocarbon dating | access-date=2008-02-19 | url-status=live | archive-url=https://web.archive.org/web/20071209151357/http://www1.phys.uu.nl/ams/Radiocarbon.htm | archive-date=2007-12-09 }}</ref> PTBT = [[Partial Nuclear Test Ban Treaty]].]]
The above-ground [[nuclear test]]s that occurred in several countries in 1955-1980 (see [[List of nuclear tests]]) dramatically increased the amount of {{sup|14}}C in the atmosphere and subsequently the biosphere; after the tests ended, the atmospheric concentration of the isotope began to decrease, as radioactive CO{{sub|2}} was fixed into plant and animal tissue, and dissolved in the oceans.

One side-effect of the change in atmospheric {{sup|14}}C is that this has enabled some options (e.g. [[Bomb pulse|bomb-pulse dating]]<ref>{{cite journal|url=https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/3713|title=Bomb-Pulse Dating of Human Material: Modeling the Influence of Diet|journal=Radiocarbon|volume=52|issue=2|pages=800–07|url-status=live|archive-url=https://web.archive.org/web/20141020085949/https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/3713|archive-date=2014-10-20|date=August 2010| vauthors = Stenstrom K, Georgiadou E |doi=10.1017/S0033822200045811|doi-access=free|bibcode=2010Radcb..52..800G }}</ref>) for determining the birth year of an individual, in particular, the amount of {{sup|14}}C in [[tooth enamel]],<ref>{{cite journal | url=http://news.nationalgeographic.com/news/2005/09/0922_050922_nuke_body.html | title=Radiation in Teeth Can Help Date, ID Bodies, Experts Say | journal=National Geographic News | date=2005-09-22 | url-status=dead | archive-url=https://web.archive.org/web/20070425080623/http://news.nationalgeographic.com/news/2005/09/0922_050922_nuke_body.html | archive-date=2007-04-25 }}</ref><ref>{{cite journal | vauthors = Spalding KL, Buchholz BA, Bergman LE, Druid H, Frisén J | title = Forensics: age written in teeth by nuclear tests | journal = Nature | volume = 437 | issue = 7057 | pages = 333–334 | date = September 2005 | pmid = 16163340 | doi = 10.1038/437333a | s2cid = 4407447 | bibcode = 2005Natur.437..333S }}</ref> or the carbon-14 concentration in the lens of the eye.<ref>{{cite journal | vauthors = Lynnerup N, Kjeldsen H, Heegaard S, Jacobsen C, Heinemeier J | title = Radiocarbon dating of the human eye lens crystallines reveal proteins without carbon turnover throughout life | journal = PLOS ONE | volume = 3 | issue = 1 | pages = e1529 | date = January 2008 | pmid = 18231610 | pmc = 2211393 | doi = 10.1371/journal.pone.0001529 | veditors = Gazit E | doi-access = free | bibcode = 2008PLoSO...3.1529L }}</ref>

In 2019, [[Scientific American]] reported that carbon-14 from nuclear testing has been found in animals from one of the most inaccessible regions on Earth, the [[Mariana Trench]] in the Pacific Ocean.<ref>{{cite web | vauthors = Levy A | url = https://www.scientificamerican.com/article/bomb-carbon-has-been-found-in-deep-ocean-creatures/ | title = 'Bomb Carbon' Has Been Found in Deep-Ocean Creatures | work = Scientific American | date = 15 May 2019 }}</ref>

The concentration of {{sup|14}}C in atmospheric CO{{sub|2}}, reported as the {{sup|14}}C/{{sup|12}}C ratio with respect to a standard, has (since about 2022) declined to levels similar to those prior to the above-ground nuclear tests of the 1950s and 1960s.<ref>{{cite news |last1=Jones |first1=Nicola |title=Carbon dating hampered by rising fossil-fuel emissions |url=https://www.nature.com/articles/d41586-022-02057-4 |access-date=5 November 2023 |publisher=Nature News |date=27 July 2022}}</ref><ref>{{cite journal |last1=Graven |first1=H. |last2=Keeling |first2=R. |last3=Xu |first3=X. |title=Radiocarbon dating: going back in time |journal=Nature |date=19 July 2022 |volume=607 |issue=7919 |page=449 |doi=10.1038/d41586-022-01954-y |pmid=35854150 |bibcode=2022Natur.607R.449G |url=https://www.nature.com/articles/d41586-022-01954-y}}</ref> Though the extra {{sup|14}}C generated by those nuclear tests has not disappeared from the atmosphere, oceans and biosphere,<ref>{{cite journal |last1=Caldeira |first1=K. |last2=Rau |first2=G.H. |last3=Duffy |first3=PB |title=Predicted net efflux of radio- carbon from the ocean and increase in atmospheric radiocarbon content |journal=Geophysical Research Letters |date=1998 |volume=25 |issue=20 |pages=3811–3814 |doi=10.1029/1998GL900010 |doi-access=free |bibcode=1998GeoRL..25.3811C }}</ref> it is diluted due to the [[Suess effect]].