Joining the Elders by Skype, Swedish activist Sara (pictured on-screen with fellow Younger Pedro) spoke of widespread cynicism about the power of the United Nations to drive the change that is needed. She asked the Elders how they respond to people who say that a huge failure at Rio+20 would actually be better than a merely weak outcome.

Mary Robinson, who is the former UN High Commissioner for Human Rights, said that in her experience, the UN system is frustrating but essential. However, she noted, the UN does respond to pressure from civil society – so the efforts of activists like Sara are very important.

Gro Harlem Brundtland, who led the World Commission on Environment and Development in the 1980s and served as UN Special Envoy on Climate Change from 2007-2010, agreed: "The UN isn't perfect, but it's what we have."

23-year old Marvin from Beijing spent time with Mary Robinson discussing sustainability issues and his work to raise awareness among his peers in China.

Read more about Marvin's work at http://www.theelders.org/article/meet-youngers-marvin

The Youngers sought advice from Gro Harlem Brundtland and Mary Robinson – two veteran change-makers – on mobilising civil society around sustainable development.

The Elders too were keen to hear from their young counterparts about the work they are doing in their home countries and internationally – and particularly their use of new tools like social media – to raise awareness and engage young people on these urgent issues.

Esther (right) and Marvin joined six members of The Elders: Martti Ahtisaari (centre), Ela Bhatt, Lakhdar Brahimi, Gro Harlem Brundtland, Jimmy Carter (left) and Mary Robinson.

Together they discussed the upcoming Rio+20 summit, the role of the UN, and how to mobilise civil society – especially young people – around sustainable development issues.

At the public debate in Oslo, Marvin asked Archbishop Tutu what his secret power is that enables him to keep on fighting in his efforts for peace and freedom.

Archbishop Tutu responded, “One of the most incredible sources of energy for me is when I am with young people – sorry oldies! You and your comrades are what gives me hope.”

He added, “I have no doubt at all that you are going to succeed where we failed.”

Asked what mistakes the Elders have regretted, Mary Robinson said that it had been a mistake to talk about sustainability and climate change in terms of “the science and the environment and melting glaciers and cuddly polar bears on ice floes; not people”.

What’s important, she emphasised, is how climate change and inequality affect people and livelihoods.

Esther Agbarakwe spoke about her motivation to engage Nigerian youth in decision-making processes.

"Young people were not really involved in issues of environmental governance. They were not aware and the government did not think about them as moral stakeholders. We saw what our peers were doing around the world, in industrialised countries like the US and Australia, and we wanted to also make sure that our voices are heard!"