We can't say we didn't know
The world’s scientists have spoken. Clearly and unequivocally when the IPCC released the first part of its fifth assessment report—known in the field as AR5—summarizing years of research by climate scientists around the world and distilling it into 2216 pages that reflect what we know about what’s happening to the planet. The word “authoritative” doesn’t begin to describe it.
Given this is first and foremost a scientific report, there are many graphs and figures attesting to the fact that the climate is changing, but for most of us, two have great significance.