Can We Go Extinct?

Recently, on television, I saw Steven Hawking talking about some of the most plausible ways mankind can go extinct, he said that over time the odds of a cataclysmic event add up, and that in the next one thousand years those odds increase to near inevitability, the program stated that the biggest risk to our, Human, race is  global warming, this threat has already brought the polar bear inches from extinction. It is a known fact that humans are the ones behind this trend, and I have a possible solution, we NEED a more effective way to harness electricity and hydrogen powered vehicles, but since we cannot reverse these effects we should find a way to populate a lifeless planet (maybe we could use closed environments on Mars or some other planet). The next greatest risks include Nuclear Holocaust, Biological weapons, and very large meteors plumeting to earth. It is not a matter of whether or not we survive, it is how long we can last.