BBC: Forests around the world will need to be expanded by 5-15% to limit global temperature rises to 2C. And crop yields must rise by 40-60%. These are just two predictions for 2050 of an online tool developed by the government to consider options for cutting carbon emissions. The Global Calculator uses data reviewed by international experts to look at scenarios for meeting the 2C target, which scientists say is needed to avoid dangerous climate change. Led by the Department of Energy and Climate...