By Phil Mercer
BBC News, Sydney
Scientists warn Australia is particularly vulnerable
Thousands of demonstrators have rallied across Australia to demand greater government action to protect the environment from climate change.
The National Climate Emergency Rallies called on Australia to take the lead at the UN environment summit in December in Copenhagen.
Activists also want an end to Australia's dependence on cheap and plentiful supplies of coal.
It is one of the world's worst per capita emitters of greenhouse gases.
Protesters were urged to wear red to highlight the risks of global warming.
In Sydney, rally organiser Moira Williams said that a coalition of trade unions and religious groups, as well as students and environmental campaigners, was pushing for immediate action.
"We need to be making these alliances and be stronger than the fossil fuel industry that currently has such a strong grip on climate policy in Australia.
"That is the positive in this rally and in this year - that we need to build that movement and it does need to come from the ground up, because at the moment we are not seeing any action from the top down."
Scientists have warned that Australia is particularly vulnerable to the effects of a shifting climate.
As temperatures increase, there are predictions that coastal communities will be threatened by rising sea levels, while other parts of the country could suffer more severe droughts, cyclones and bushfires.
The government in Canberra has repeatedly stressed that tackling climate change is a priority.