40 Years of Mauna Loa CO2 Data from Keeling

The 40th anniversary of the atmospheric CO2 work being done at the Mauna Loa Observatory, Hawaii, by Dr. Charles D. Keeling, of the Scripps Institution of Oceanography (SIO) at the University of California, San Diego, was celebrated in 1997. At a White House ceremony held in July 1997, Dr. Keeling was presented with a "special achievement award" from Vice President Al Gore. According to the Online SIO Press Release, Scripps Scientist Receives Science Award from Vice President Al Gore, Dr. Keeling was honored "for 40 years of outstanding scientific research associated with monitoring of atmospheric carbon dioxide in connection with Mauna Loa Observatory."

Widely recognized as the "Keeling curve", the Mauna Loa atmospheric CO2 concentration measurements, taken since 1958 and now extending through 1997, constitute the longest, continuous record of atmospheric CO2 concentrations available in the world and are considered to be a reliable indicator of the regional trend in the concentration of atmospheric CO2 in the middle layers of the troposphere. The methods and equipment used to obtain these measurements have remained essentially unchanged during the 40-year monitoring program. The CO2 concentrations taken at Mauna Loa Observatory are obtained using a nondispersive, dual detector, infrared gas analyzer. The Mauna Loa record shows a 15.2% increase in the mean annual concentration, from 315.83 parts per million by volume (ppmv) of dry air in 1959 to 363.82 ppmv in 1997. Each year, the atmospheric CO2 concentration varies between a high value in winter (because of biospheric respiration) and a low value in summer (because of drawdown by photosynthesis); thus, a wave-like pattern is superimposed on the year-to-year increasing trend.

In 1984, Dr. Keeling made available to CDIAC, a tentative data set, Atmospheric CO2 Concentrations--Mauna Loa Observatory, Hawaii 1958-1983. The availability of this landmark numeric data package (NDP), NDP-001, was announced in April 1984; it became CDIAC's first NDP, as well as one of the most widely recognized and utilized data sets in the CO2 research community.

At the end of Fiscal Year 1984, CDIAC had responded to a total of 18 requests for NDP-001. Since then, Dr. Keeling's atmospheric CO2 record from Mauna Loa has become one of the most sought after data products available from CDIAC and continues to be one of our most requested products. CDIAC has now responded to over 10,000 requests for the Mauna Loa atmospheric CO2 data through the NDP-001 data package and through Trends: A Compendium of Data on Global Change.

The following monograph, referenced in the Trends series, has been cited in over 300 papers:

Keeling, C.D., R.B. Bacastow, A.F. Carter, S.C. Piper, T.P. Whorf, M. Heimann, W.G. Mook, and H. Roeloffzen. 1989.
A three-dimensional model of atmospheric CO2 transport based on observed winds: 1. Analysis of observational data. In D.H. Peterson (ed.), Aspects of Climate Variability in the Pacific and the Western Americas. Geophysical Monograph 55:165-235.

The U.S. Department of Energy (DOE) began providing support funding for Dr. Keeling's study of atmospheric CO2 in the late 1970's. This funding continues today by DOE's Environmental Sciences Division of the Office of Biological and Environmental Research.