We are no doubt living in challenging times, with cities so often the focal point of social tensions that are felt well beyond their limits. But cities also offer us so many solutions. For the good of their entire countries today and tomorrow, we need national leaders to seize the new urban opportunity, writes Nick Stern.

The climate crisis does not begin or stop with Africa, but African countries can play a leadership role in seizing the opportunities of a better future. The world's larger economies have a responsibility to unlock this future, for themselves and for others, writes Ngozi Okonjo-Iweala.