Number of natural world heritage sites at serious risk from global warming has doubled in three years, says the IUCN, including the Great Barrier Reef and spectacular karst caves in Europe

Mount Kilimanjaro - a natural wonder at risk from climate change as its glaciers shrink.
Mount Kilimanjaro - a natural wonder at risk from climate change as its glaciers shrink. Photograph: khanbm52/Getty Images/iStockphoto