Choose the best answer:
Forget global terrorism - for most of the world's population, ticking time bombs like earthquakes, supervolcanoes and hurricanes pose a far greater threat. Natural disaster expert Bill McGuire reveals a few of the top catastrophes waiting to happen. With NASA's eminent climate scientist, Jim Hansen, concerned that collapsing polar ice sheets could result in sea levels rising 1-2m this century and several more in the next, prospects for the Earth's coastal zones are bleak. A 1m rise would threaten one third of the world's agricultural land, while a 4m rise would maroon Miami 60km offshore. Rising sea levels is not the only threat to coastal regions. The Cumbre Vieja volcano on the Canary Island of La Palma is slowly creeping seawards. During a future eruption, this gigantic landslide will plunge into the ocean, pushing up a bulge of water close to a kilometre high, spawning a mega-tsunami capable of devastating all the coastal areas surrounding the North Atlantic. Coastal regions also face the menace of desertification. By 2030, over half a billion people living around the shores of the Mediterranean will be viewing the encroaching desert with increasing panic. An area bigger than the UK, and home to 16 million people, is threatened - by the end of the century- with transformation from a green and pleasant land to a baking wilderness of sand and rock. However, these disasters seem pale in comparison to the mega-catastrophes waiting to happen like supervolcanoes, for instance. Every 50 millennia or so, a colossal volcanic blast expels sufficient ash and gas to cover a continent and block the Sun's rays for years on end, heralding a bitter volcanic winter. At Yellowstone in Wyoming, US, two such super-eruptions have shattered the crust in the last 2.1 million years and the volcano there remains restless. An asteroid attack is another threat which would have devastating consequences. A total of 713 asteroids with diameters of 1km or more, and the potential to clobber the Earth at some future date, have been identified. A 2km asteroid would load the atmosphere with dust and trigger a sustained global freeze. Harvests would fail and billions would die. Fortunately, such collisions only happen every couple of million years.
2. According to Jim Hansen, what is an outcome of polar ice caps melting?
