The potential human costs of climate change have been underestimated, according to the United Nations Development Program (UNDP) 2007-2008 Human Development Report. Calling global climate change the defining development challenge of the 21st century, UNDP stresses that it could leave hundreds of millions of the poorest citizens in the poorest countries malnourished and lacking adequate supplies of safe drinking water, as well as facing ecological threats and a loss of livelihoods.












