Earth Hour 2007: Sydney's one-hour blackout becomes a global climate ritual

In 2007 Australians largely accepted climate change but had no cheap, easy way to act on it; WWF-Australia had a small budget and needed a gesture anyone could join.

Make climate concern visible: get a whole city to switch off its lights for one hour on the same night, turning a private worry into a shared, photographable act.

On 31 March 2007, 2.2 million residents and 2,000 businesses switched off for the hour while the Opera House and Harbour Bridge went dark; the ritual returned yearly and by 2008 reached 50 million people in 400 cities across 35 countries.

The first night drew 2.2 million participants; by 2009 it was called the world's largest grassroots movement for the environment, landmarks from the Colosseum to the Golden Gate went dark, and more than 190 countries now take part each March.

In early 2007 WWF-Australia was looking for a way to make climate concern tangible. Australians broadly accepted that the climate was changing, but there was no obvious everyday action to take, and the organisation's budget could not buy a loud campaign. So, with advertising agency Leo Burnett Sydney and The Sydney Morning Herald, it proposed something almost absurdly simple: switch the lights off for one hour.

On the evening of 31 March 2007, more than 2.2 million Sydneysiders and 2,000 businesses did exactly that. The Opera House and Harbour Bridge went dark, candlelit picnics appeared in the Royal Botanic Garden, and the city's skyline dimmed for an hour — a single, shared, photographable gesture.

The image did the work. By 2008 the event had spread to 50 million people in 400 cities across 35 countries; by 2009 it was being described as the world's largest grassroots movement for the environment, with famous landmarks worldwide switching off each March.

It gave climate concern a zero-cost, synchronous action anyone could join — no march, no donation, no expertise.

The one-hour format created a single iconic image that media and landmarks could amplify for free.

It replaced despair with agency: participants performed their care publicly instead of just feeling it.

It was designed to scale from day one — one city, then 35 countries, then a global annual ritual.

A synchronous, costless gesture can carry an entire campaign: the shared blackout is the message, the photos are the proof, and every landmark that joins scales it.

Earth Hour has run every year since and evolved into the Biggest Hour for Earth, with supporters pledging 1.4 million hours in 2024 and over 3 million in 2025. The movement also spun off concrete wins: WWF-Russia's Earth Hour petition helped pass a law protecting Russia's seas, Earth Hour forests were planted in Uganda, and Argentina created its largest marine protected area after Earth Hour pressure. By 2018, 188 countries and territories and nearly 18,000 landmarks took part.