Agence France-Presse: Carbon dioxide indirectly causes up to 50 percent more global warming than originally thought, a finding that raises questions over targets for stabilising carbon emissions over the long term, a study said on Sunday. In a paper published in the journal Nature Geoscience, British scientists said a tool commonly used in climate modelling may have badly underlooked the sensitivity of key natural processes to the warming caused by CO2. As a result, calculations for man-made global …