Greenland’s immense ice sheet is melting as a result of climate change. YOKOHAMA, Japan — Climate change is already having sweeping effects on every continent and throughout the world’s oceans, scientists reported on Monday, and they warned that the problem was likely to grow substantially worse unless greenhouse emissions are brought under control. The report by the Intergovernmental Panel on Climate Change, a United Nations group that periodically summarizes climate science, concluded that ice caps are melting, sea ice in the Arctic is collapsing, water supplies are coming under stress, heat waves and heavy rains are intensifying, coral reefs are dying, and fish and many other creatures are migrating toward the poles or in some cases going extinct. The oceans are rising at a pace that threatens coastal communities and are becoming more acidic as they absorb some of the carbon dioxide given off by cars and power plants, […]