i have seen movie few days ago and that was Last Days On earth. in this movie they ranked different factors that could cause the end of life on earth and the top factor was Drastic Envrironmental Changes.
So according to them the rapid environmental changes that are happening around as earthquick, heavy rains, floods, Hot seasons etc are the major factors which could cause the end of life on earth.
it is also fact that the temperature of globe is increasing due to many factors and this has very drastic effects as the ice on poles is melting, and so the water level of ocean is increasing, in addition there is more rains in different parts of the worlds and so on.
i would like if my fellows add more comments on this topic