This graphic, from Information Is Beautiful, shows the terrifying math of climate change, and it’s a pretty good encapsulation of the problem we face.
An increase of 1.5 degrees above pre-industrial levels is inevitable, given what we’ve already emitted. We’re now in the black-bar phase, eating up our available "carbon budget" before we hit dangerous levels of temperature rise.
Then, there are the proven reserves that oil, gas and coal companies—which, if burned, would take us beyond what scientists have said are "safe limits" (of course, what might be safe in one part of the world might not be in another). After that, you can see the projected effect on sea level rise, ocean acidification, sea ice reduction, agricultural yields, and "hurricane destructiveness." And so on.
We can continue looking at charts like this, or start doing the math.