Library Digital Collections

Scripps O2 Program Data

View Collection Items

Collections »

Scripps O2 Program Data

About this collection

Date Issued
  • 2019
Date Collected
  • 1989 - present
Cite This Work

Keeling, Ralph F. (2019). Scripps O2 Program Data. UC San Diego Library Digital Collections.


This archive presents time-series measurements of atmospheric O2/N2 ratio and CO2 mole fraction from flask samples collected by the Scripps O2 program at twelve fixed land stations. Ten of these stations form an active network from nearly Pole to Pole along a Pacific transect. The earliest results in this network (from La Jolla) date from 1989. The remaining two stations are “legacy stations”, where flasks are no longer collected. Flasks are collected under atmospheric conditions designed to minimize the impact of any local process such as fuel burning that might impact atmospheric O2 or CO2. The sampling frequency is typically ~ 2 weeks.

The O2/N2 ratio is reported as relative deviation from reference in δ units: δ = ((O2/N2)_samp /(O2/N2)_ref ) – 1, where (O2/N2)_samp is the O2/N2 mole ratio of the sample, (O2/N2)_ref is the ratio of a long-term reference. The quantity δ is multiplied by 10^6 and expressed in “per meg” units. Changes in CO2 are reported in “ppm” units, i.e. µmol CO2 per mole of H2O -free air.

The Scripps O2 program has been directed throughout its history by Prof. Ralph Keeling. The program began while R. Keeling was a postdoc at the National Center for Atmospheric Research in Boulder, Colorado, and was moved to the Scripps Institution of Oceanography in 1993.

The O2/N2 measurements are made on a custom interferometric analyzer, while the CO2 data use a Siemens non-dispersive infrared analyzer. Sampling, analysis, and calibration methods are described in Keeling et al (2007) and Keeling et al (1998).

The Scripps O2 program is operationally independent from the Scripps CO2 program in using different flasks and analysis systems. The CO2 records of these two programs are therefore substantially independent, even though the flasks for both programs are collected at many of the same stations.


3 digital objects.

Scope And Content

The Scripps O2 Program website at provides access to openly available atmospheric O2/N2 ratio and CO2 concentration data from various sources along with graphics. Redundant copies of the atmospheric O2/N2 and CO2 data from 12 sampling stations are being deposited here, through the UC San Diego Library, to provide enhanced discovery, long-term accessibility, and preservation. New data from the 10 active stations are added monthly to this collection, but the issued DOIs for each collection item will not change as these updates are added. When new calibrations are applied to the data, however, new DOIs will be issued. Data sets calculated from the latest calibration are accessible by clicking on View Collection Items from this page. Data sets using older calibrations will be accessible via 1) Related Resource links on each collection item's current landing page, and 2) the DOI originally issued for the data set.

Related Publications

Keeling, R. F. and A. C. Manning (2014). Studies of recent changes in atmospheric O2 content. Treatise on Geochemistry, Volume 5. R. F. Keeling and L. Russell. Amsterdam, Elsevier: 385-404.

Keeling, R. F., A. C. Manning, E. M. McEvoy and S. R. Shertz (1998). "Methods for measuring changes in atmospheric O2 concentration and their application in southern hemisphere air." Journal of Geophysical Research-Atmospheres 103(D3): 3381-3397.

Keeling, R. F., A. C. Manning, W. J. Paplawsky and A. C. Cox (2007). "On the long-term stability of reference gases for atmospheric O2/N2 and CO2 measurements." Tellus Series B-Chemical and Physical Meteorology 59(1): 3-14.

Manning, A. C. and R. F. Keeling (2006). "Global oceanic and land biotic carbon sinks from the Scripps atmospheric oxygen flask sampling network." Tellus 58B: 95-116.

Related Resource
  • English



The Scripps O2 program has been supported by a series of grants from the US NSF and the NOAA, most recently 1304270 and NA15OAR4320071. The program has also relied on staff from the following programs for collection of samples: Cape Grim Baseline Air Pollution, of the Canadian Greenhouse Gas program, of the US Weather Service.