Let me add another existential risk to the list.
It is 2040. Technology has advances explosively, changing the face of the planet completely. As a result disparity of affluence has completely escalated. In 2040 trends current from 2013 continue, and most people in the developed world get LESS, in relative terms than they do 30 years ago. Life is harsh and most people have to juggle a dozen dehumanizing freelance projects just to pay the bills for their coffin apartments, atmospheric purifiers, velocipede weekly payments and 3D printer feedstocks. The rich argue things have gotten better and better, but in big cities world wide people are dying in alleys from exposure, heat stroke, poverty and literal starvation.
In the harsh Neo-Randian political climate of 2043 the abilities of the state to quell unrest, enforce politically acceptable speech, education and thought is momentarily outstripped by grassroots technologies. At some moment somewhere some technology becomes available to an underclass of hysterically desperate and systemically disillusioned protesters.
One group concludes there is no more hope, and they may be correct in their assessment. They say a final salute to their example Ted Kaczinsky, and they activate some doomsday device. Within a month most human beings have died.
In this hypothetical scenario, what might be the causator of this gigadeath?
… a useless, demanding, petulant underclass of economically nonviable cyberproletariat that keeps demanding more more state services, more obamacare, higher minimum wages, more welfare, more pensions, more more more
– technology offering solutions at an ever faster pace
– the implicit aggression of a technology empowered upper class that keeps dominating critical resources and displacing the rest of humanity ?
Even more relevant – does this final suicidal act of planetary seppuku make sense?
It would to me.