Zuhura Plummer, a 36-year-old charity worker from Oxford who is taking part, said: "While we squabble over Brexit, the planet is burning".
Extinction Rebellion claims protests in the capital will be five times bigger than similar events in April.
The group wants Britain to reduce greenhouse gas emissions to net zero by 2025 rather than the government's 2050 target.
Two protesters were arrested after trying to enter the offices of Seven West Media - which houses The West Australian.
He demanded that Queensland Premier Annastacia Palaszczuk declare a climate emergency, and said he could stay for days.
"These are the key principles that unite activists across the planet".
"I hope to hear from them [leaders] about a very strong plan to take action to meet this crisis", said Kubrin.
XR, which originates in the United Kingdom, promised a protest "five times larger" than the massive one it held in London in April. They are telling us to panic.
Climate change activists protest at the Wall Street Bull in Lower Manhattan during Extinction Rebellion protests in New York City, New York, US, October 7, 2019.
More than 1,000 people attended an "opening ceremony" at Marble Arch on Sunday evening, featuring meditation and dancing as "inspiration" prior to the protests. Groups of artists held a procession and protesters were told to "surround" the upcoming demonstrations with love.
A spokesperson says police were pleased in general with the behaviour of protestors in the city.
He said: "The Government does not seem to be doing anything, or even recognising climate change so this seems the only way forward - non violent direct action, seems the way to go".
We are expecting many more arrests at the rebellion in October and would like these rebels to know that support is already in place should they need it.