The doctrine of "first, do no harm" is the basis of the Hippocratic Oath, one of the world's oldest codes of ethics. It governs the work of physicians -- but climate and health campaigner Shweta Narayan says it should go further. In this essential talk, she highlights the interdependence of environmental and human health and emphasizes the necessity of placing health at the heart of all climate solutions. "It's impossible to have healthy people on a sick planet," she says.