Editing Keeling Curve (section)

== Background ==
Prior to the 1950s, measurements of atmospheric {{CO2}} concentrations had been taken on an [[ad hoc]] basis at a variety of locations. In 1938, engineer and amateur meteorologist [[Guy Stewart Callendar]] compared datasets of atmospheric {{CO2}} from [[Kew]] in 1898–1901, which averaged 274 parts per million by volume ([[Parts-per notation|ppm]]),<ref>{{Cite journal|last1=Brown|first1=Horace Tabberer|last2=Escombe|first2=F.|date=1905|title=On the variations in the amount of carbon dioxide in the air of Kew during the years 1898-1901|journal=Proc. R. Soc. Lond. B|language=en|volume=76|issue=507|pages=118–121|doi=10.1098/rspb.1905.0004|bibcode=1905RSPSB..76..118B|issn=0950-1193|doi-access=|s2cid=97664092 }}</ref> and from the eastern [[United States]] in 1936–1938, which averaged 310 [[Parts-per notation|ppm]], and concluded that {{CO2}} concentrations were rising due to [[Anthropogeny|anthropogenic]] emissions.<ref>{{Cite journal|last=Callendar|first=Guy Stewart|date=1938|title=The artificial production of carbon dioxide and its influence on temperature|url=https://www.eas.ualberta.ca/jdwilson/EAS372_15/exams/Callendar_QJRMS1938.pdf|journal=Quarterly Journal of the Royal Meteorological Society|volume=64|issue=275|pages=223–240|doi=10.1002/qj.49706427503|bibcode=1938QJRMS..64..223C|access-date=2018-11-24|archive-date=2020-11-12|archive-url=https://web.archive.org/web/20201112015420/https://www.eas.ualberta.ca/jdwilson/EAS372_15/exams/Callendar_QJRMS1938.pdf|url-status=dead}}</ref> However, [[Guy Stewart Callendar|Callendar]]'s findings were not widely accepted by the scientific community due to the patchy nature of the measurements.<ref name="Fleming">{{cite book|title=Historical Perspectives on Climate Change|last1=Fleming|first1=James Rodger|date=1998|publisher=[[Oxford University Press]]|isbn=978-0195078701|location=Oxford}}</ref><ref>{{Cite web|url=https://history.aip.org/history/climate/co2.htm#SC|title=The Carbon Dioxide Greenhouse Effect|website=history.aip.org|language=en|access-date=2018-11-24}}</ref>

[[Charles David Keeling]], of the [[Scripps Institution of Oceanography]] at [[UC San Diego]], was the first person to make frequent regular measurements of atmospheric CO<sub>2</sub> concentrations in [[Antarctica]], and on [[Mauna Loa]], [[Hawaii]] from March 1958 onwards.<ref name=":2">{{Cite journal|last=Harris|first=Daniel C.|date=2010|title=Charles David Keeling and the Story of Atmospheric CO<sub>2</sub> Measurements|journal=Analytical Chemistry|volume=82|issue=19|pages=7865–7870|doi=10.1021/ac1001492|pmid=20536268|issn=0003-2700}}</ref> Keeling had previously tested and employed measurement techniques at locations including [[Big Sur]] near [[Monterey]], rain forests of the [[Olympic Peninsula]] in [[Washington (state)|Washington state]], and high mountain forests in [[Arizona]].<ref name="UCSD" /> He observed strong [[Diurnal cycle|diurnal]] behavior of CO<sub>2</sub>, with excess CO<sub>2</sub> at night due to [[Respiration (physiology)|respiration]] by plants and soils, and afternoon values representative of the "free atmosphere" over the [[Northern Hemisphere|Northern hemisphere]].<ref name="UCSD" />