By Daphne Psaledakis and Michelle Nichols UNITED NATIONS (Reuters) – Countries on the front lines of the climate crisis are fed up. During the annual gathering of world leaders at the United Nations this week, low-lying island nation Vanuatu stepped up a fight to get the world to focus on combating global warming by calling for a fossil fuel nonproliferation treaty. “The time is up – action is required now,” Vanuatu’s President Nikenike Vurobaravu told the U.N. General Assembly on Friday. The treaty would aim to scale down coal, oil and gas production to limit the rise in temperatures to the g…