[Chief climate adviser to the German government Hans Joachim] Schellnhuber and his WBGU colleagues go a giant step beyond the findings of the Intergovernmental Panel on Climate Change, the UN body whose scientific reports are constrained because the world's governments must approve their contents. The IPCC says that rich industrial countries must cut emissions 25 to 40 percent by 2020 (from 1990 levels) if the world is to have a fair chance of avoiding catastrophic climate change. By contrast, the WBGU study says the United States must cut emissions 100 percent by 2020?i.e., quit carbon entirely within ten years. Germany, Italy and other industrial nations must do the same by 2025 to 2030. China only has until 2035, and the world as a whole must be carbon-free by 2050. The study adds that big polluters can delay their day of reckoning by "buying" emissions rights from developing countries, a step the study estimates would extend some countries' deadlines by a decade or so.