After recent devastating bushfires, dozens of Extinction Rebellion climate activists gathered outside Sydney's iconic Opera House on Sunday to protest against climate change.

Australia is the world's driest continent after Antarctica and scientists say that leaves the country particularly vulnerable to weather extremes associated with global warming.

"We should all be out every day because it really is a state of emergency," claimed one woman taking part in the protest. "And I'm so worried about the future of all of us and all of us who have children. We're just leaving them this terrible, terrible, terrible world."

"We've got no choice," another protester added. "I mean, you've seen the air over the last few weeks. This is unprecedented fire conditions. And it's not just Australia. It's Indonesia, Amazonia, it's also happening in the Arctic. The Earth is on fire. If we don't wake up now, we're going to lose it."

Earlier this week Sydney was shrouded in a smokey haze as dozens of bushfires ripped across the state of New South Wales. The haze was so thick in some places that it was 11 times worse than the level considered hazardous.

Scientists have warned that emissions of planet-warming greenhouse gases need to start dropping sharply as soon as possible to prevent global temperatures rising more than 1.5 degrees Celsius (2.7 Fahrenheit) by the end of the century.

So far, the world is on course for a 3-5 degrees Celsius rise, with potentially dramatic consequences for many countries.