Nature World: In his State of the Union address Tuesday night, President Barack Obama renewed his call to curb US carbon emissions and promised a shift toward cleaner energy production practices in the US. Obama cited the need to continue reducing carbon emissions produced by burning fossil fuels, an echo from the State of the Union address a year ago when he promised he would start tackling climate change with, or without, the help of Congress. "Over the past eight years, the United States has reduced our total...