Protesters chanting "Green energy" demonstrated outside the G20 finance ministers' summit on Sunday, calling for climate change to be on the world's biggest economies' agenda as part of an international day of action.
More than 100 people wearing green paper hearts around their necks gathered in a colourful demonstration amid tight security outside the forum venue in the northern Australian city of Cairns.
They repeatedly chanted "Every dollar spent, every single cent, 100 percent, green energy" and carried banners including one that read: "Add climate change to the G20."
"I'm here because I'm a parent, I'm here because I'm a scientist, I understand what climate change means for our planet, our children, our economy, our health," said John Rainbird, an Australian biologist.
"This is a threat that needs the same kind of mobilisation that we are taking against many of the other threats that are undermining people's security at the moment. It poses the same threat, it's just not so obvious."
Geoff Holland, a Cairns community activist who addressed the crowd near a row of armed police officers, was unhappy that Australia's Prime Minister Tony Abbott was not attending the United Nations' Climate Summit in New York on Tuesday.
"None of the G20 countries are taking responsibility. They are still representing the interests of extremely powerful fossil fuel corporations," he said.
The climate protest was among the first of many expected to take place on Sunday around the world ahead of the UN summit.
UN Secretary General Ban Ki-moon is expected to join the demonstration in Manhattan, at which an estimated 100,000 people are expected to attend.