When Nelson Mandela formed the Elders in 2007 to promote peace and human rights across the world, he challenged us to be bold and to give a voice to those who have none. No issue demands these qualities more than our collective failure to tackle climate change. Climate change is the biggest challenge of our time. It threatens the well-being of hundreds of millions of people today and many billions more in the future. It undermines the human rights to food, water, health and shelter — causes for which we, as Elders, have fought all our lives.