Sydneysiders have reacted well to a call to turn off the lights for an hour, in an organised strike against global warming.

Across the city the lights slowly dimmed at 7.30pm on Saturday the 31st of March, with the Opera House and the Harbour Bridge the focus of attention as they closed into semi-darkness.

Organisers say it is Australia's biggest environmental demonstration of action against climate change.

This initiative is part of World Wildlife Fund's campaign to combat global warming, the goal being to reduce Australia's greenhouse emissions by 30 per cent by 2030.

Sky News is just one of more than a thousand businesses taking part.

Others involved can be found on the website www.earthhour.com.au.