Two premiers have questioned the effectiveness of protesters to stop climate change as thousands of activists disrupted major cities in a bid to force governments to declare a climate emergency.

Dozens of Extinction Rebellion demonstrators including former Greens senator Scott Ludlam have been arrested since protests began on Monday, with marchers blocking roads and causing other disruptions in Australian capitals in the latest action on Tuesday.

Activists from Extinction Rebellion participate in a protest in Sydney on Tuesday. Credit:AAP

They want governments to reduce greenhouse gas emissions to zero within five years and insist they have a moral duty to raise the alarm.

But Queensland Premier Annastacia Palaszczuk's office questioned their methods for saving the planet, adding her government regularly spoke out on climate change and had a 50 per cent renewable energy target for 2050.