Kumi Naidoo exudes a warmth he clearly feels for humanity and the planet that accommodates us. And it is with that warmth that he expresses the cold harsh reality of a future determined by an unwillingness to act. "Our political leaders need to understand that nature does not negotiate," he said.

Two degrees has long been cited as the magic number in the debate over the level of global warming, but to ask the South-African born leader of Greenpeace whether it is enough, would be to elicit a categorical "no".

"If we want to prevent dangerous climate change, prevent sea level rise, agricultures being wiped out, we need to bring the line below 2 degrees as far as possible." Continuing to talk in terms of two degrees, he argues, is simply providing more time to burn more carbon. And that scenario is met with another firm "no".

"Our leaders should have the courage to take unpopular decisions and stand up to the interests of the fossil fuel companies," he said, adding that the fossil fuel era has had its day and that it is time to "embrace fully the renewable energy era."

The first African to head Greenpeace, Kumi Naidoo is no stranger to moments of historic change. As a young man he fought against Apartheid, and was expelled from high school as a consequence. But that did not stop him from going on to complete his doctoral thesis at Oxford University. Indeed he was studying there, when Nelson Mandela was released from prison and elected president. Naidoo later worked with Mandela on South Africa's constitution.

It is with that same determination for justice that he addresses the issues of the planet. "We have lived in a world of division for far too long, and we must use climate change as an opportunity to break this division and recognize that we must get this right as a global family."

Failure to do so will result in suffering, not just for the poor countries of the world, but ultimately for everyone. As such, he says the climate change struggle is about whether humanity can fashion a new, mutual and inter-dependent relationship for centuries to come.

"We always talk about saving the planet. Well, I've got good news for you. The planet does not need saving. If we continue the way we are, we will warm up the planet to a point that we will be gone as human beings. But once that happens and we are out of the way, forests will recover, oceans will replenish and so on."