Early oil industry knowledge of CO2 and global warming

To the Editor — In a seminal 1960 article in the journal Tellus, Charles Keeling reported that the concentration of atmospheric CO2 at the South Pole was rising at a rate “nearly that to be expected from the [global] combustion of fossil fuel”1. His measurements, begun in 1957, allowed him to start constructing the famous Keeling curve — the continuous, direct record of rising CO2 levels around the globe caused primarily by the burning of fossil fuels. Yet archival documents show that even before Keeling published his measurements, oil industry leaders were aware that their products were causing CO2 pollution to accumulate in the planet’s atmosphere in a potentially dangerous fashion. And when US President Lyndon Johnson's Science Advisory Committee warned of global warming in 1965, the petroleum industry’s main trade association, the American Petroleum Institute (API), relayed the warning to its members.

In 1954, the geochemist Harrison Brown and his colleagues at the California Institute of Technology submitted a research proposal to the API entitled “The determination of the variations and causes of variations of the isotopic composition of carbon in nature.” The scientists proposed the use of new mass spectrometers to investigate the ratio of carbon-12 to carbon-13 in terrestrial, marine and mineral systems to understand geological and biological carbon cycling.

The team had already carried out preliminary work, including on tree rings of various ages. “Perhaps the most interesting effect concerning carbon in trees which we have thus far observed,” the researchers reported to the API, “is a marked and fairly steady increase in the 12C/13C ratio with time.” The results indicated that fossil fuels had caused atmospheric CO2 concentrations to rise by about 5% over the past century2. Brown’s estimate was quite accurate: from 1854 to 1954, global CO2 concentrations had risen by 10% (from around 285 to 313 ppm)3, with about 4% of that from fossil fuels and the remainder from deforestation and other land-use changes4.

That same year, in 1954, the Yale ecologist George Hutchinson suggested using carbon isotopes to measure atmospheric CO2 from fossil fuels5. However, Brown’s research proposal, reproduced in Fig. 1 and never before noticed by historians, shows that such measurements had already been performed — and reported to petroleum industry leaders.

Fig. 1: Excerpt of research proposal to the API from Harrison Brown and colleagues in 1954.

The proposal informed the API that fossil fuels had caused atmospheric CO2 levels to rise by about 5% over the last 100 years. Image reproduced from ref. 2, Caltech Archives.

In 1955, the API began funding the proposed research at Caltech under the name Project 53. The project focused on uranium–lead dating, yet work on carbon continued, at least for a time: later that year, the researchers told the API that they were using their mass spectrometer to make around 2,300 measurements on CO2 per year6. The results were not published.

Others began examining fossil fuel emissions using carbon isotopes in tree rings. Hans Suess, in 1955, gave a low estimate of atmospheric fossil carbon7 of less than 1%. Suess’s work was expanded in 1957 by H. R. Brannon of Humble Oil Company (now ExxonMobil), who found higher concentrations of 3.5%. Brannon knew of Harrison Brown's unpublished work, compared results and found that they agreed8.

A few years later, in 1959, petroleum industry leaders were notified of the danger of CO2 accumulation by the physicist Edward Teller, who warned them of global temperature and sea-level rise by the end of the century9. Thus, even before early portions of the Keeling curve were published in 1960, leaders of the API and other segments of the oil industry were informed that fossil fuel products were causing atmospheric CO2 concentrations to rise, and that such a rise was potentially dangerous.

When that danger was brought to US President Lyndon Johnson’s attention by his Science Advisory Committee's Restoring the Quality of Our Environment report in 1965, the petroleum industry took notice10. Three days after the report’s publication, API president Frank Ikard addressed industry leaders at the organization’s annual meeting, saying, “One of the most important predictions of the report is that carbon dioxide is being added to the Earth's atmosphere by the burning of coal, oil, and natural gas at such a rate that by the year 2000 the heat balance will be so modified as possibly to cause marked changes in climate beyond local or even national efforts”11. Ikard did not dispute the links between fossil fuels, CO2 and global warming. “The substance of the report,” he summarized, “is that there is still time to save the world's peoples from the catastrophic consequence of pollution, but time is running out.” This communication, reproduced in Fig. 2, has also remained unnoticed by historians until now.

Fig. 2: Excerpt of address given by API President Frank Ikard at the organization's annual meeting in 1965.

Ikard informed the API's membership that the US President’s Science Advisory Committee had predicted that fossil fuels would cause significant global warming by the end of the century. Reproduced from ref. 11, American Petroleum Institute.

These archival discoveries add to the growing body of information regarding fossil fuel producers’ knowledge of climate science over time12. Such information may assist in understanding the history of climate policy efforts and assessing the responsibilities of fossil fuel producers today13.


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This research was supported by the Center for Climate Integrity and the Stanford University Department of History. T. Boughton of the University of Wyoming is thanked for providing the image for Fig. 2.

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Correspondence to Benjamin Franta.

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Franta, B. Early oil industry knowledge of CO2 and global warming. Nature Clim Change 8, 1024–1025 (2018). https://doi.org/10.1038/s41558-018-0349-9

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