The Controversy about the Role of Trees in Climate Change

At the UN's climate summit today in Nairobi, Kofi Annan said there's a "frightening lack of leadership" against global warming. But conflicting reports show how hard it is to know what works and what doesn't. One study says the world's depleted forests are coming back. Forests are regarded as "carbon sinks" that absorb carbon dioxide, one of the major greenhouse gases. Another study says the forests may not absorb much carbon dioxide, despite conventional wisdom. That could have major impact on the multi-billion dollar business of global "carbon trading." We learn more about the controversy over the role of trees in climate change.