Africa had been thought to be a potentially large carbon sink — of great value in efforts to mitigate carbon dioxide emissions.  But an analysis now reveals that it could be a net source of greenhouse gases that will increase global warming. Writing in Nature magazine, the international weekly journal of science, Dr. Cheikh Mbow, Senior Scientist, Climate Change and Development at the World Agroforestry Centre says One of the biggest challenges in curbing climate change is to obtain robust estimates of greenhouse-gas emissions and sequestration. you can read his article here