Earth reached a grim milestone this week: levels of atmospheric CO₂ reached 415 parts per million (ppm) for the first time since humans developed agriculture 10,000 years ago, primarily thanks to a colossal rise of industrial activity in the 1800s, which ramped up further following World War II.

While relentlessly creeping carbon dioxide levels is hardly a surprise to hear, it certainly won’t be a shock to scientists at the oil and gas giant Exxon, whose climate models predicted this – pretty much to a T – over 35 years ago.

In 2015, Inside Climate News published a widely acclaimed series of articles called Exxon: The Road Not Taken that investigated Exxon's engagement with the mounting evidence of fossil fuel's role in global warming and climate change in the late 1970s and early 1980s. They managed to get their hands on some leaked internal documents from Exxon, including a 1982 climate memo that predicted atmospheric CO₂ levels in 2019 would reach about 415 parts per million – which is exactly what we saw happen this week.

The same graph also estimates that global average temperature will increase by approximately 1°C by 2020, another milestone that was reached back in 2015.

The whole of the Exxon: The Road Not Taken series is a fascinating, and oddly prophetic, piece of work. In the late 1970s, Exxon budgeted over $1 million on a 3-year project to map the effects of atmospheric carbon dioxide and develop better climate models. By the early 1980s, their top scientists and statisticians were persistently telling executives that fossil fuel combustion was messing with carbon dioxide levels and leading to climate change. "Fossil fuel combustion and the clearing of virgin forests (deforestation) are believed to be the primary anthropogenic contributors" to the greenhouse effect, the 1982 report says.

However, the warnings were doubted, played down, or spun.

Another part of the investigation shows how Exxon actively planted doubt about climate change using rhetoric and buzzwords you can still hear today used by climate skeptics: “uncertainty,” “just a theory,” “inconclusive evidence,” and “bias”.

Exxon, which became ExxonMobil in 1999, kept up this game for decades and only publically recognized climate change and its link to fossil fuels in the 2000s. In one of their earliest public acknowledgments, ExxonMobil put out a report and press release in 2014 that warned investors about the risks of climate change.

Now, they have changed their tune and developed an outlook that’s more or less in line with the scientific consensus that climate change is tightly linked to fossil fuel combustion. They even expressed support for the Paris Climate Agreement. Needless to say, they also deny any wrongdoing, even in the '70s and '80s. Their official corporation stance argues there has been an “extremely well-funded” conspiracy that “seeks to delegitimize ExxonMobil and misinterpret our climate change position and research.”

[H/T: Tom Randall]