Alok Jha is a science and environment correspondent at the Guardian newspaper, specialising in green technologies. In addition to writing news and comment, he presents the Science Weekly podcast and looks after the Guardian's science website. He graduated with a physics degree from Imperial College London and is also the author of How to Live Forever. He lives in London.

• HUMAN THREATS: Mass extinction; Global pandemic; The Doomsday machine; Mutually assured destruction; Terrorism; Death by euphoria; Overpopulation; Population death spiral. TECH: Cyberwar; Biotech disaster; Nanotech disaster; Artificial superintelligence. ENVIRONMENT: Transhumanism; Death of the bees; Invasive species; Desert Earth; Global food crisis; Water wars; Resource depletion; Environmental collapse; Rising sea levels; The Gulf Stream shuts down; Snowball Earth; Chemical pollution; Ozone destruction; Asteroid impact; Mega tsunami; Supervolcano; Oxygen depletion; Geomagnetic reversal; Superstorms. SPACE: Sun storms; Polar shift; Lethal space dust; Runaway black hole; Gamma rays from space; Vacuum decay; Solar collision; Scientists create a black hole; Hostile extraterrestrials; Death of the sun; Galactic collision; The end of time; Strangelets. GENETICS: Genetic superhumans; Dysgenics; Organic cell disintegration. THE FUTURE: It's all a dream; Information extinction; Unknown unknowns. Index.

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