Giant Space Rocks: An impact with a comet or asteroid from space may be the most likely doomsday scenario – giant space rocks have done serious damage here on earth before. The extinction of the large dinosaurs 65 million years ago is thought to have been caused by the impact of a massive fireball from space, up to 15 kilometres wide, that caused either a sizzling global heat-wave or a freezing global winter (scientists aren’t sure.) The good news in 2012 is that astronomers have ruled out any threats from space for the rest of the year – and at any time in the foreseeable future.
Super Volcanoes: The Mount St Helens eruption in the US in 1980, one of the largest volcanic eruptions in recent history, released 24 megatonnes of energy – about 1,600 times the force of the atomic bomb dropped on Hiroshima in 1945. But the Mount St Helens blast would be just a firecracker compared to a “supervolcano” (or “megavolcano”) eruption, which could be up to 1,000 times as violent. The eruption would also propel millions of tonnes of ash into the atmosphere, blocking out the sun for years. The potential threats include the volcanoes of the Rabaul caldera in Papua New Guinea (such as Tavurvur, pictured above), and the Popacatapetal caldera beneath Mexico City.
Nuclear Annihilation: The chances of a global nuclear catastrophe have shrunk since the end of the Cold War 15 years ago, but there are still enough nuclear weapons in world arsenals to destroy the whole planet several times over in the next week or so. Although the global stockpile of H-bombs has been cut dramatically from the high point of 65,000 warheads in 1985, more than 19,000 functioning nuclear warheads still remain, with about 2,000 warheads ready to launch at any time and another 3,000 on operational standby.
Global Methane Burps: Some scientists fear that a global rise in sea temperature could trigger the sudden release of massive reserves of methane gas from the sea floor and polar permafrost zones – resulting in runaway global warming that could make the world rapidly inhospitable for humans. One scientist has even warned of massive explosions of burning methane erupting from the sea, so at least the end of the world in this doomsday scenario could be spectacular – more of a bang than a whimper.
Mad Science: High-energy experiments like the Large Hadron Collider (LHC) in Europe are plumbing the limits of the known universe by recreating the phenomenally high temperatures that existed at the time of the Big Bang, 14 million years ago. No-one’s entirely sure what they will find, which leaves some very slight room for concern that such experiments could create swarms of miniature black holes that could grow to consume the earth, or might even spark a supernova – assuring the swift annihilation of everything for about a million miles around. Last year a court in Germany dismissed a lawsuit by a small group of scientists who wanted to shut down the LHC, in case it all goes wrong and brings about the end of the world.