Theories for the end of the world as told by present day scientists include that the earth , when it is close to its end , will experience extreme sun 's heat as the result of excessive global warming, which is increasing day by day.
Then , the ocean levels will increase , due to the melting of glaciers on the poles of the Earth. After that it mentions about ecological imbalance , and natural disasters. You would now be surprised to know that Vedas too , describe the end of the World in a similar way.The Vedas explain that the Earth will be heated by the warmth equal to that of twelve suns , then the whole world will be submerged by water, there will be famines , floods and disasters all around.
When the entire human race is suffering from this , Lord Kalki appears as the destruction of the world. And in fact , it marks the end of Kalyug, according to various Puranas .