Finally, evidence of something that all of us knew- Exxon executives knew that carbon dioxide was a greenhouse gas since the early 80s. Think of all of the progress in alternative and renewable energy sources that could have been made in three decades, using the money that Exxon and the other fossil fuel businesses used to fund climate change denialism, not to mention all of the money and (more importantly) lives thrown away in order to secure or steal fossil fuel sources.
Three decades of lost ground, lost momentum, and lost lives... let that sink in for a brief moment. Three decades of knowingly committing Gaiacide. I have often likened fossil fuels to "startup capital" to be used to kick off a mature energy economy based on a variety of safer renewable energy sources, but the short-term profits of the fossil fuel companies have long trumped the prospects of long-term human survival.
It's obvious that the oil and coal companies knew that continued burning of fossil fuels would be a problem, just like it's obvious that the tobacco companies knew that smoking caused lung cancer, it's pretty appalling to finally see one of the "smoking guns" exposed.