I first met Nelson Mandela when I was in my late 20s, in 1993. I was helping facilitate an African National Congress (ANC) workshop to plan its media strategy. I went down to meet him for the first time and you know me I got stupid... I just choked. I said, "Hello Madiba, it's a real honour to meet you," and I couldn't get another word out.

I was 15 years old when I first heard the name Mandela, or Madiba, as he is fondly known in Africa. In apartheid South Africa he was public enemy number one. Shrouded in secrecy, myth and rumour, the media called him 'The Black Pimpernel'.

This week we saw progressive business and faith leaders making strong commitments that are moving ahead of what world leaders promised today. The leaders of major economies must be bolder than they were today in providing a vision for 100% renewable energy for all.

Currently, we allow our political and business leaders to get away with murder. Now is the time to change that. We need direct liability for those who are destroying our future and this planet. We need fast, profound and systemic change. History only moves forward when courageous people get up and act. That's why I support this citizens' initiative to recognise ecocide as the crime it is.

In Durban, where I was born and grew up, and all over Africa, Nelson Mandela was a hero! Now he is a hero to the world.

My final advice for young people is to not wait for leadership from adult politicians. Step forward today, because our current leaders are denying the dire reality we are facing. Leadership can come form anywhere.

Nelson Mandela also spoke about how, as a human being, he's made mistakes.