UN Secretary-General Ban Ki-moon will urge world leaders to make bold pledges to tackle climate change when they get together for a major summit in New York.
It's expected 120 heads of state and government will attend the meeting on Tuesday. Foreign Minister Julie Bishop will represent Australia.
Prime Minister Tony Abbott has been criticised in some quarters for not attending, despite arriving in New York the next day for a special sitting of the UN Security Council.
US President Barack Obama will address the climate summit, which is seen as a crucial stepping stone to Paris in 2015, where organisers hope a new global deal for combating global warming will be finalised.
Hundreds of thousands of people around the world - including Mr Ban in New York - rallied at the weekend demanding world leaders take urgent action on climate change.