More than 500 people rallied for Newcastle's first Walk Against Warming on Saturday, calling on world leaders to come to a "fair, ambitious and binding" global agreement to reduce global warming.

Climate Action Newcastle spokeswoman Zoe Rogers said the Rudd Government should avoid lobbying in the back rooms at Copenhagen to water down global frameworks, clinging to its addiction for fossil fuels.

Instead, leaders needed to commit to deep emission cuts of at least 40 per cent by 2020, Ms Rogers said.

"The science demands that emissions peak by 2020 and decline immediately," she said.

Walkers showed support for small Pacific Island nations at Copenhagen.

"Tuvalu has proposed that a second treaty be considered in addition to the existing Kyoto Protocol, which only covers 30 per cent of emissions," Ms Rogers said.

NSW Greens MLC Lee Rhiannon and Newcastle councillor Michael Osborne joined the walk from Wheeler Place to Customs House. It was one of at least 3000 similar events held worldwide.