One of the possible solutions to Fermi's Paradox (if the Universe is filled with intelligent species, where are they all?) has always been to suggest that advanced civilizations tend to bring about their own destruction.
Adam Korbitz suggests two possible mechanisms by which this might happen here on Earth:
First, researchers at the University of Colorado have published a study showing that even a limited nuclear exchange between longtime rivals India and Pakistan would have devastating environmental effects --- although it would by no means spell the end of the human race.
Second, the World Health Organization issued a warning today about the catastrophic human death toll that unchecked climate change may cause this century, particularly in the poorest countries.
Of course my favorite solution to F's Paradox is that they are already among us - but they call themselves Hungarians.
(A slow news day, obviously)