List of near-term global threats to all or many human lives, health and property. Roughly in order of this site's estimated likelihood of threat will kill 10 million people or more in the next century or so:
(2013-12-08: ver. 1, subject to revision)

1. Anthropogenic Global Climate Change (sometimes referred to as "Global Warming")
2. Non-sustainable farming methods leading to draught and famine
3. Pollution/ecosystem damage
4. Nuclear War
5. Global financial calamity
6. Nuclear Reactor Disaster
7. Asteroids/Meteors/Comets
8. Large/Super-Volcano explosion, earthquakes, tsunamis and other natural disasters, both in their direct effects and indirect consequences.
9. War in general.
10. Deliberate killing of populations outside of officially declared wars.
11. Non-sustainable farming methods leading to emergence of unstoppable or almost unstoppable superbugs.
12. Other/hard-to-predict
13. Release of Biological War Pathogens (whether deliberate or not)