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Exxon’s climate predictions were remarkably accurate, but ignored

A new study by scientists at Harvard University and the Potsdam Institute for Climate Impact Research has reviewed the climate studies conducted or paid for by the oil and gas company currently known as ExxonMobil. The study, published in the peer-reviewed journal Science, dives deeply into the company data from the late 1970s onwards (before Exxon and Mobil joined forces), in order to assess the accuracy of the climate projections produced by or on behalf of Exxon over several decades. 

The results of the investigation are summarized in one single chart that displays every global warming projection reported by Exxon and ExxonMobil scientists between 1977 and 2003. The authors of the study collected their data from previously unreported information and models buried in the company’s own documents. They conclude that the projections are startlingly accurate and reveal that the company knew just how much global warming would occur and the damage that was attributable to the burning of fossil fuels. 

In fact, the scientists have put a number on what ‘Exxon knew,’ decades ago, about climate science: that the burning of fossil fuels would lead to 0.20 ± 0.04 degrees Celsius of global warming per decade. 

Although it has been widely reported that Exxon has known about the threat of global warming since the 1970s, this study is the first quantitative review of the company’s early climate science. Previous research focused on Exxon’s inconsistent internal and external rhetoric on climate change, and the fact that the oil company understood the science before it became a public issue and then spent millions to promote misinformation.

“We find that most of their projections accurately forecast warming consistent with subsequent observations,” the report concludes. “Their projections were also consistent with, and at least as skillful as, those of independent academic and government models.”

The researchers used established statistical techniques that are also used by the Intergovernmental Panel on Climate Change (IPCC), the United Nations body that is responsible for assessing the science related to climate change. The researchers found that 63–83 percent of global warming projections reported by ExxonMobil scientists were consistent with subsequently observed temperatures changes. Moreover, projections modeled by ExxonMobil scientists had an average ‘skill score’ of 72 ± 6 percent, with the highest scoring 99 percent. 

For comparison, NASA scientist Dr. James Hansen’s global warming predictions, presented to the U.S. Congress in 1988, had skill scores ranging from 38 percent to 66 percent. (When we account for differences between forecast and observed atmospheric CO2 levels, the ‘skill score’ of projections modeled by ExxonMobil scientists was 75 ± 5 percent, with seven projections scoring 85 percent or above. Again, for comparison, Hansen’s 1988 projections had corresponding skill scores of 28 to 81 percent.)

The study finds that “Exxon and ExxonMobil Corp also correctly rejected the prospect of a coming ice age, accurately predicted when human-caused global warming would first be detected, and reasonably estimated the ‘carbon budget’ for holding warming below 2°C. On each of these points, however, the company’s public statements about climate science contradicted its own scientific data.”

It is clear from the study’s analysis that this company, the world’s largest oil and gas company, was in possession of accurate and reliable scientific information in the 1970s and 80s, and understood that mankind was indeed influencing the global climate through carbon dioxide release from the burning of fossil fuels. However, this did not stop the company from spending decades refusing to publicly acknowledge climate change and even promoting climate misinformation.

For example, in June 1988, when NASA scientist James Hansen told a congressional hearing that the planet was already warming, Exxon stated publicly that the science was still controversial. By 1989, the company had helped create the Global Climate Coalition (disbanded in 2002) to question the scientific basis for concern about climate change. It also helped to prevent the U.S. from signing the international treaty on climate known as the Kyoto Protocol, in 1998, to control greenhouse gases. 

The findings of the current study add weight to ongoing legal and political investigations into ExxonMobil and the extent to which the company’s personnel sowed doubt about the scientific basis for climate change predictions.

“These findings corroborate and add quantitative precision,” the authors write, “to assertions by scholars, journalists, lawyers, politicians, and others that ExxonMobil accurately foresaw the threat of human-caused global warming, both prior and parallel to orchestrating lobbying and propaganda campaigns to delay climate action, and refute claims by ExxonMobil Corp and its defenders that these assertions are incorrect.”

“This is the nail-in-the-coffin of ExxonMobil’s claims that it has been falsely accused of climate malfeasance,” commented study lead author Geoffrey Supran of Harvard University . “Our analysis shows that ExxonMobil’s own data contradicted its public statements, which included exaggerating uncertainties, criticizing climate models, mythologizing global cooling, and feigning ignorance about when – or if – human-caused global warming would be measurable, all while staying silent on the threat of stranded fossil fuel assets.”

An article published in the Guardian in 2019 finds that ExxonMobil is one of 20 companies responsible for one-third of energy-related global carbon emissions since 1965. In addition, half of the greenhouse gas emissions in our atmosphere were released after 1988. What a difference it would have made if the fossil-fuel companies, including ExxonMobil, had been upfront about this and had been part of the solution instead of the problem. We are likely to have been in much better environmental shape than we are now. 

By Alison Bosman, Staff Writer

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