A GM scientist presented her findings to at least three high-level executives at the company, including a former chairman and CEO. It’s unclear whether similar warnings reached the top brass at Ford.

But in the following decades, both manufacturers largely failed to act on the knowledge that their products were heating the planet. Instead of shifting their business models away from fossil fuels, the companies invested heavily in gas-guzzling trucks and SUVs. At the same time, the two carmakers privately donated hundreds of thousands of dollars to groups that cast doubt on the scientific consensus on global warming.