The oil company Exxon “knew” since the 70s the effects of global warming despite denying it for decades

Climate projections made by ExxonMobil scientists between 1977 and 2003 were accurate and skillful in predicting global warming later and contradicted the company’s public claims, according to a new study from Harvard University (United States) published in the journal ‘Science’. In the first systematic evaluation of the fossil fuel industry’s climate projections, researchers from Harvard University and the Potsdam Institute for Climate Impact Research have put a figure on what “Exxon knew” decades ago about the science of climate: that burning fossil fuels would cause global warming of 0.20 +- 0.04 degrees Celsius per decade.

The findings, summarized in a single chart showing all global warming projections reported by Exxon and ExxonMobil Corp scientists between 1977 and 2003, are based on statistical analysis of never-before-reported data hidden in the company’s own documents. Although it has been widely reported that Exxon knew about the threat of global warming since the 1970s, this study is the first quantitative review of the company’s initial climate science. Previous investigations focused on Exxon’s inconsistent internal and external rhetoric on climate change.

This report dives into the company’s data and reveals that the company knew with surprising accuracy how much the planet was going to warm up. “Most of their forecasts were in line with subsequent observations,” the report concludes. “Their projections were also consistent with, and at least as adept at, those of independent academic and government models.” Using statistical techniques established by the IPCC, the study concludes that between 63% and 83% of global warming projections reported by ExxonMobil scientists coincided with the temperatures observed later.

In addition, projections modeled by ExxonMobil scientists had an average “skill score” of 72 +- 6%, and the highest score was 99%. By way of comparison, NASA scientist Dr. James Hansen’s global warming predictions presented to the US Congress in 1988 had scores ranging from 38% to 66%. Accounting for differences between forecasts and observed atmospheric CO2 levels, the “skill score” of projections modeled by ExxonMobil scientists was 75 +- 5%, with seven projections scoring 85% or higher.

Again, for comparison, Hansen’s 1988 projections had corresponding ability scores of 28 to 81%. The study concludes that “Exxon and ExxonMobil Corp also correctly rejected the prospect of a coming ice age, they accurately predicted when human-caused global warming would first be detected and reasonably estimated the ‘carbon budget’ for keeping warming below 2ºC. On each of these points, however, the company’s public statements on climate science contradicted its own scientific data.”

The study adds weight to the ongoing legal and policy investigations into ExxonMobil. “These findings corroborate, and add quantitative precision,” the authors write, “to the claims by academics, journalists, lawyers, politicians and others that ExxonMobil accurately anticipated the threat of human-caused global warming, both before and in parallel with orchestrating lobbying and propaganda campaigns to delay climate action, and refute claims by ExxonMobil Corp and its advocates that these claims are incorrect.”

“This is the nail in the coffin of ExxonMobil’s claims that it has been falsely accused of climate tampering,” says lead author and Harvard University Research Associate Geoffrey Supran (Supran began as an Associate Professor of Environmental Science and Policy at the Rosenstiel School of Marine, Atmospheric, and Earth Sciences in University of Miami Jan 2023). “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—global warming human-caused would be measurable, all while remaining silent about the threat of stranded fossil fuel assets.”