9News understands the man intends to drop the banner and light a flare from the top of the spire – about 162 metres off the ground.
There are a number of police on the scene, as well as Arts Centre members.
Extinction Rebellion spokesperson Jane told Today the banner bore the slogan “occupy for climate” and would also show the dates for “the next period of rebellion”.
“The concern is the same as always – that is, that we are heading for out-of-control warming, potentially quite soon,” she said.
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Jane said the group’s next Melbourne protests would be in the Melbourne CBD in May, where they would be camping in the park.
She said the “disruption” by the group would be minimal compared to that caused by climate change.
Extinction Rebellion has been criticised for previous protests, including people super-gluing themselves to busy metropolitan roads.
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