There's no doubt that Stephen Hawking is one of the most brilliant scientists to have ever lived. There's also no doubt that he enjoys giving his opinion on topics of which he knows absolutely nothing.
A few years ago, Dr. Hawking got into trouble for claiming, "Philosophy is dead." It was a strange thing for a theoretical physicist to assert, not only because theoretical physics has direct implications for philosophy but because the entire scientific enterprise is predicated upon epistemology. (That's the philosophical discipline that seeks to answer one of the most important questions humanity has ever asked: How do we know what we claim to know?)
Dr. Hawking has also proposed that, if aliens exist, they're probably like the ones from Independence Day that will murder everybody and take our stuff.
So, it shouldn't come as a complete surprise that Dr. Hawking has a dire pronouncement for humanity. In an upcoming documentary, he says that humans will need to find a new planet on which to dwell within 100 years if we want to survive. Why? According to International Business Times, humans must abandon Earth "to survive situations like climate change, asteroid strikes, epidemics and overpopulation."
He's wrong on every single count.
Climate change. There isn't a single worst-case scenario in which our planet becomes too hot for humans to inhabit. Earth is not about to become Venus... or Waterworld.
Asteroid strikes. The astrophysicist Ethan Siegel once commented, "It is very, very likely that we will have no major asteroid impacts on Earth over the next 1,000 years, let alone the next 100. It is very likely that there will be no species-threatening impacts over the next 10 million years. [Original emphasis]"
Epidemics. Because of economic development and advances in public health, infectious diseases will decline, not increase. We have already eradicated smallpox, and polio may go extinct, too. Emerging infectious diseases, like Ebola, can be scary but will come nowhere near threatening the existence of humanity. The biggest threats are from pandemic influenza and antibiotic-resistant bacteria, but neither represents a threat to the survival of mankind. (Even the Black Death only managed to kill 1/3 of Europe.)
Overpopulation. Demographers believe that the human population will hit approximately 11 billion in the year 2100. However, because population growth is slowing (and has been for decades), it is likely that the human population will peak and then decline sometime thereafter. In other words, humans are not cockroaches; we will not keep reproducing until we're out of food.
Dr. Hawking's beliefs, therefore, aren't just wrong, but are far outside the scientific mainstream. It's too bad that this intelligent man keeps making headlines for all the wrong reasons.