This world clock provides plenty to think about.
[kml_flashembed movie="http://www.poodwaddle.com/worldclock.swf" height="800" width="800" /]
Click on the buttons across the top. Click the “NOW” button and watch the clock for a minute. How many people have been born and how many have died? Look at hoe much oil has been pumped out of the ground and how many hectares of forested land has been cleared.
Poodwaddle, who host this clock, say that the data comes from various official sources – including the World Health Organisation and the United Nations. While they don’t provide any verifiable information (that I could see) the graphical nature of this clock could be a useful way to start a discussion.