Key points:
- A new Harvard study is the first to put a number on what Exxon knew decades ago regarding fossil fuel burning and its impact on climate change.
- Exxon’s climate change projection models were more accurate than those presented to NASA by experts.
- Through public statements, however, Exxon directly contradicted its own internal scientific data.
Climate projections reported by ExxonMobil scientists between 1977 and 2003 were accurate and skillful in predicting subsequent global warming and contradicted the company’s public claims, a new Harvard study shows.
According to the study published in Science, Exxon knew fossil fuel burning would lead to 0.20 ± 0.04 degrees Celsius of global warming per decade.
As previously reported, Exxon knew about the threat of global warming since the 1970s, keeping projections and reports up until 2003.
“We find that most of their projections accurately forecast warming consistent with subsequent observations,” reads the new report by Harvard researchers. “Their projections were also consistent with, and at least as skillful as, those of independent academic and government models.”
The study finds that 63 to 83% of global warming projections reported by ExxonMobil scientists were consistent with subsequently observed temperatures. Moreover, projections modeled by ExxonMobil scientists had an average “skill score” of 72 ± 6%, with the highest scoring 99%. 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% to 66%.
The study also shows that Exxon correctly rejected the prospect of a coming ice age, and estimated the carbon budget for holding warming below 2°C. However, Exxon’s internal scientific data were in direct opposition to the company’s public statements about climate science.
“This is the nail-in-the-coffin of ExxonMobil’s claims that it has been falsely accused of climate malfeasance,” said lead author Geoffrey Supran, who was a research associate at Harvard and is now a professor at the University of Miami. “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.”
Information provided by Harvard.