Tens of thousands march over climate change

Tens of thousands of protesters have marched in Melbourne's CBD calling on world leaders to take action on climate change.

Organisers of a climate change rally in Melbourne say tens of thousands will take to the streets. (AAP)

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More than 40,000 protesters have marched in Melbourne's CBD calling on leaders to take action on climate change.

They held signs bearing slogans including "Climate Change is not Cool", "There is no planet B" as they packed into the steps of the State Library shutting down roads during the evening's peak hour.

Geoff Cousins, president of the Australian Conservation Foundation, says the protest sends a message to politicians that "words are no longer sufficient, action is now necessary".

Melbourne was the first port of call in a series of ACF rallies around Australia to flag concerns as global leaders heading to the United Nations climate summit in Paris from November 30 until December 11.

Mr Cousins also welcomed Labor's pledge on Friday to cut carbon emissions by 45 per cent on 2005 levels by 2030, well over the Coalition pledge of 26 to 28 per cent.

Police have not reported any arrests during the protest.