The world has emitted extra greenhouse gases this century equivalent to the annual totals of China and the United States above a maximum for avoiding the worst of climate change, a study estimated on Tuesday. Global accounting firm PriceWaterhouseCoopers said in the report that almost all major nations, including European Union countries that pride themselves on climate policies, were lagging since 2000 in a push for low-carbon growth. It said the world was already far above a "budget" of total emissions of 1,300 billion tons of carbon dioxide from 2000-50 which it estimated as the maximum permissible while avoiding the...