Among those people taking part were Princess Birgitta of Sweden, David Miller, mayor of Toronto, Tom Miller, deputy mayor of Portland, Romel Pascual, deputy mayor of Los Angeles, and Amos Masondo, mayor of Johannesburg.
David Miller said Toronto had been working on practical ways to lower greenhouse gas and carbon emissions, and was aiming to create a low carbon economy. The city has asked people to separate food waste and recycle rubbish, which has saved energy, cut pollution and helped preserve the environment.
Tom Miller said cities accounted for 3 per cent of the world's population, but 80 per cent of greenhouse gases.
Pascual said everyone could do something each day to help to reduce our carbon footprint and that businesses could move into solar power, to create new jobs and encourage greener forms of energy. David Miller said that, rather than using nuclear power as a major energy source, the world should focus on generating energy locally through sources such as wind, wave, geothermal, and solar power.
Princess Birgitta urged people around the world to tackle climate change, which was the most pressing problem facing the earth.
The effects of global warming were described as lethal and, while measures were being taken around the world, they were not enough at present: every person, government, and nation of the world had to play a part. "Please help us with this," the princess said.