Almost any headline these days tells us how the world's outlook seems gloomy.

Population growth, climate change, poverty: the problems of the world seem insurmountable.

But not everyone agrees.

In his new book, Jeffrey Sachs, a special adviser to the UN secretary general and director of the Earth Institute, claims that with international will and cooperation, all these crises can be averted.

Also, Emily Morris from the Economist Intelligence Unit tells Sir David what the changes in Cuba really mean.