Ars Technica has an article stating that the current carbon emissions "dwarf" those the last time the Earth experienced such emissions 56 million years ago. According to the article, while the total quantity matches what was released, the rate of CO2 emission today is 10 times greater than what it was during the Palaeocene-Eocene Thermal Maximum, or PETM. The article's conclusion is the most interesting: "we are altering our environment in an unprecedented (and unpredictable) way."
I think the results are going to be predictable in the sense that our world is going to change so rapidly and drastically over the next few decades into a world that it will make the world we were living in before the twentieth century look like paradise. We already live in empty sprawling environments where all that's left at our feet is concrete, asphalt, and the litter of our society. In spite of the current economic mess we're in, our numbers and our corrupting civilization continues to spread relentlessly like a blight across the land.