The first problem would be that many of the places where people live and grow food would no longer be suitable for either. Rising sea levels - from thermal expansion of the oceans, melting glaciers and storm surges - would drown today's coastal regions in up to 2 metres of water initially, and possibly much more if the Greenland ice sheet and parts of Antarctica were to melt. "It's hard to see west Antarctica's ice sheets surviving the century, meaning a sea-level rise of at least 1 or 2 metres," says climatologist James Hansen, who heads NASA's Goddard Institute for Space Studies in New York. "CO2 concentrations of 550 parts per million [compared with about 385 ppm now] would be disastrous," he adds, "certainly leading to an ice-free planet, with sea level about 80 metres higher... and the trip getting there would be horrendous."......
Half of the world's surface lies in the tropics, between 30° and -30° latitude, and these areas are particularly vulnerable to climate change. India, Bangladesh and Pakistan, for example, will feel the force of a shorter but fiercer Asian monsoon, which will probably cause even more devastating floods than the area suffers now. Yet because the land will be hotter, this water will evaporate faster, leaving drought across Asia. Bangladesh stands to lose a third of its land area - including its main bread basket.....
All of the world's major deserts are predicted to expand, with the Sahara reaching right into central Europe.
Glacial retreat will dry Europe's rivers from the Danube to the Rhine, with similar effects in mountainous regions including the Peruvian Andes, and the Himalayan and Karakoram ranges, which as result will no longer supply water to Afghanistan, Pakistan, China, Bhutan, India and Vietnam.......
Along with the exhaustion of aquifers, all this will lead to two latitudinal dry belts where human habitation will be impossible, say Syukuro Manabe of Tokyo University, Japan, and his colleagues. One will stretch across Central America, southern Europe and north Africa, south Asia and Japan; while the other will cover Madagascar, southern Africa, the Pacific Islands, and most of Australia and Chile......