Every ten days another billion tons of carbon dioxide are released.  And to equilibrate to current CO2 levels the planet still needs to warm by half a degree.

Meeting in Paris in 2015, world leaders decided that the two-degree threshold was too high; the stated aim of the climate accord is to hold “the increase in the global average temperature to well below 2°C” and to try to limit it to 1.5°C

Every ten days another billion tons of carbon dioxide are released.  And to equilibrate to current CO2 levels the planet still needs to warm by half a degree.

So what did Exxon know? “There is general scientific agreement that the most likely manner in which mankind is influencing the global climate is through carbon-dioxide release from the burning of fossil fuels,” James Black, an Exxon scientist, told company executives in 1977. “Present thinking holds that man has a time window of five to ten years before the need for hard decisions regarding changes in energy strategies might become critical.” Five years later, an internal report declared that without “major reductions in fossil fuel combustion,” a number of “potentially catastrophic” events, such as the eventual flooding of “much of the US East Coast, including the State of Florida and Washington D.C.,” could occur. The changes wouldn’t come for decades, the report said, but “once the effects are measurable, they might not be reversible.”

It quickly became clear that Exxon had not only done the most robust climate research but had also sown doubt about climate change.

The journalistic investigations, published in late 2015 by InsideClimate News and the Los Angeles Times, which collaborated with Columbia, made it clear that while Exxon’s scientists acknowledged the inherent uncertainty in predicting the future, they said that the scientific community had reached consensus and that Exxon had an “ethical responsibility” to study the problem and make its findings public. The company seemed to agree, spending $1 million in 1979 to outfit a supertanker with equipment to analyze carbon-dioxide levels along the ship’s route between the Middle East and the Gulf of Mexico.

Mike MacCracken, a former government scientist whose great-grandfather, coincidentally, was John D. Rockefeller’s legal counsel. (“We still have the silver tea set he gave my great-grandfather,” MacCracken told me.) MacCracken had worked with Exxon in the 1980s and ’90s and said its research was among the best, citing a 1985 report that concluded that the Earth would warm two to five degrees Celsius by 2100. “That’s exactly what we’d say today,” MacCracken said.

By the late ’80s, the rest of the world had begun to grasp the problem; for 1988, Time named the “Endangered Earth” its second-ever nonhuman “Person of the Year,” after “The Computer.” By then, Exxon and other fossil-fuel companies had begun factoring climate change into their business decisions. “We considered climate change in a number of operational and planning issues,” Brian Flannery, Exxon’s in-house climate adviser at the time, told the Columbia reporters. In 1989, Shell raised a natural-gas platform in the North Sea by several feet to accommodate rising sea levels, while engineers designing a pipeline owned by several companies, including Exxon, said they would have to account for the “considerable increase of the frequency of storms as a result of climate change.” A researcher at an Exxon subsidiary even argued that climate change offered a silver lining as the company looked for oil in the Arctic: “Potential global warming can only help lower exploration and development costs.”