How can the human race survive the next hundred years?

In a world that is in chaos politically, socially and environmentally, how can the human race sustain another 100 years?
Update: Yahoo! Answers staff note: This is the real Stephen Hawking. Look here for more detail:
http://blog.360.yahoo.com/blog-d8pH0dcoRKeB12yOcnUQp.9VCFos?p=6628
Update 2: Yahoo! Answers Team Update: We've created a group for you to discuss this important issue in more detail. Find out more at:
http://groups.yahoo.com/group/humansurvival/
Update 3: Hear Dr. Stephen Hawking's message to the Yahoo! Answers community here:
http://video.yahoo.com/video/play?vid=178f89d3d9987efabcf31c6fb8364fd6.654968
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