SYDNEY, Nov 14 (Reuters) - Adapting to a sea level rise of up to 0.5 metres (1.64 feet) will cost the three most vulnerable Pacific atoll nations nearly $10 billion - equivalent to about 20 years of gross domestic product - the World Bank said in a report on Thursday. Kiribati, Tuvalu and Marshall Islands are among the smallest, most remote and dispersed countries in the world, spread across 6.4 million square kilometres (2.47 million square miles) of Pacific Ocean, where residents live at an...