Rapidly rising levels of greenhouse gases are already having a major impact on the earth’s natural systems and the problem is likely to grow significantly worse unless these emissions are brought under control, according to a new report by the Intergovernmental Panel on Climate Change (IPCC). The report, released in Yokohama, Japan, said that steadily rising temperatures are melting polar ice caps, sharply diminishing Arctic sea ice, intensifying heat waves and heavy rains, causing the death of coral reefs, and placing water and food supplies under stress. The report on climate impacts, drafted by several hundred of the world’s leading climate scientists, emphasized that the world’s food supply is at considerable risk. Already, the report said, heat waves and water stress are affecting the output of wheat and corn on a global scale, impacts that are only expected to intensify in the future, further exacerbating food shortages. “Nobody on this planet is going to be untouched by the impacts of climate change,” said IPCC chairman Rajendra K. Pachauri.