Business Green: Leaders with the "courage and vision of John F Kennedy" will need to emerge from both the business and political spheres if work to decarbonise the economy by 2050 is to secure the popular support it requires, one of the UK’s leading sustainability experts has claimed. During a discussion at The Carbon Show yesterday, Dr Gary Kendall, executive director of think tank SustainAbility, said that only " visionary and ambitious" leadership would reduce the world’s reliance on oil, drawing …