Archbishop Desmond Tutu has launched a petition calling for British prime minister David Cameron and Secretary-General of the United Nations Ban Ki-moon to respond urgently to climate change by setting a renewable energy target of 100% by 2050.“Climate change is one of the greatest moral challenges of our time,” wrote Tutu. “It threatens the health of our planet and people; especially the poorest and most vulnerable. It threatens our children’s future and everything we hold dear. It is time for all of us to wake up and take action together — in our local communities, nationally and globally, as well as in our daily lives.“As citizens motivated by faith and other moral traditions, we recognize that there is a grave obligation to act on climate change.“We call on you as leaders to respond urgently to the threats of climate change and set a renewable energy target of 100% by 2050. We need bold action like this to keep global temperature rise below the unacceptably dangerous tipping point of two degrees, to phase out carbon pollution to zero, and to invest resources in sustainable development pathways to build a more flourishing, inclusive and balanced world.“We pledge to do our own part by embracing the moral responsibility to care for our world and for each other and by seeking to live better and more sustainable lives in greater joy and harmony.“Let us act now, boldly and together, to build a better life for all!”To sign the petition, click here.