The global warming icon for the ubx. (Photo credit: Wikipedia)

Considering that we can survive in the harshest environment, from the hottest desert to a frozen sea of ice. We now have the technology to resist even worst conditions, in a few hundred years space colonies will be a reality and in a few thousand year we will probably have mastered terraforming and will be able to gather energy directly from the stars.

Lots of bad things could happen in the mean time, epidemics, floods , global warming, name it. But you have to remember that we are now over 6 billions and we use to be less than 5,000. So anything bad that happens that leaves 1 in a million of us alive means we can survive.