Lots of people in a short amount of time
I first saw this video at a Hyatt HR conference I was speaking at. They were launching a change initiative for their hotels to become more "eco-friendly" and they used this to highlight the urgency in doing so. I thought of it recently and have posted it here. It is a graphic description produced by Population Connection of world population growth from 1 A.D.
Be patient as it "ticks" through the world's slowly expanding population growth and subsequent rise and fall of empires. Then take note of the velocity of the growth beginning around 1900. It is simply staggering.