New research finds human activity has caused temperatures in Greenland to rise far beyond levels seen in the 20th century. The study in the journal Nature found that without immediate action to stop global heating, Greenland’s melting glaciers will raise sea levels by 20 inches by the end of the century, flooding coastal communities around the world. Researchers studying ice cores found first decade of the 21st century was the warmest for Greenland’s ice sheet in a thousand years. Temperatures in some parts of Greenland now average 1.5 degrees Celsius above preindustrial levels.