A list of possible senarios

1. Ecological Meltdown- Depletion of fresh water which could lead to drought, disease, and water wars. Loss of Top Soil and Deserfication reduction in food production and supply, famine, disease.

2. WW3- The increase in terrorist activity and the world wide distrobution of WMDs. Nuclear Holocaust.

3.Climate Change- another world wide ice age, which could lead to senario 1 & 2.

4. The Frankinstein Effect- We are destroyed by our own out of control creations. Superviruses, Nanotech Assemblers, A.I, Computer Viruses shutting down the IT networks across the globe, etc.

5. Comet/Asteriod collision- The most popular one.

6. Super Volcano- I.E YellowStone National Park, or the Canary Islands. Eruptions covering the globe in a blanket of ash.

7. Super Tsunami- Since most of the world major Population Centers are on Coastlines this could be a threat.

8.Major Ozone Depletion- From CFC gases causing a Ecological Meltdown

9.Alien Invasion- Another Popular one

10. A Cosmic Disaster- A wandering black hole, or Nearby Supernova