It’s something of a voluntary rolling blackout: Communities around the globe are going dark for an hour on Saturday evening as part of an initiative called “Earth Hour” to raise awareness of climate change.

In more than 7,000 cities and towns across the planet, millions of residents are turning off their lights for an hour from 8:30 to 9:30 p.m. local time to show their environmental concern.

An advertisement for the event warns: “The world is using the equivalent of one and a half planets to support life on Earth.  Earth Hour was born out of a hope that this could change.”

The rest of the video appears to advertise a worldwide dance party with glow sticks, coupled with challenges from celebrities and international activists.

“I will conduct a free yoga class if 500 people upload their own [Earth Hour] challenge,” Victoria’s Secret supermodel Miranda Kerr pledged.

Here’s the full promotional video:

And here are some photos of “Earth Hour” observances:

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

The ‘London Eye’ and London skyline can be seen before (left) and after (right) the population of the city observed Earth Hour on Saturday, March 23, 2013. (Photo: AP)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

The Elizabeth Tower, which houses Big Ben at the Houses of Parliament in London, after the lights were turned off to mark Earth Hour 2013, Saturday March 23, 2013. (Photo: AP)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

A combination picture shows (from top left to right) the ancient Temple of Parthenon atop the Acropolis hill before and during the Earth Hour in Athens on March 23, 2013. (Photo: AFP/Getty Images)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

The lights are turned off at the Kremlin during the worldwide Earth Hour in Moscow, Russia, Saturday, March 23, 2013. (Photo: AP)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

The Empire State Buidling (CR) stands dark as its lights were turned off too mark ‘Earth Hour’ in New York, March 23, 2013. (Photo: AFP/Getty Images)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

In this combo photo large electronic billboards stand dark (bottom) on Times Square as their lights were turned off too mark ‘Earth Hour’ in New York, March 23, 2013. (Photo: AFP/Getty Images)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

Combination photo shows The Eiffel Tower submerging into darkness at 8:30 pm (local time) as part of the Earth Hour switch-off on March 23, 2013 in Paris. (Photo: AFP/Getty Images)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

This picture shows people standing next to candles arranged to read ‘Tunisia’ in the Habib Bourguiba avenue after submerging into darkness as part of the Earth Hour switch-off in Tunis on March 23, 2013. (Photo: AFP/Getty Images)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

The lights on the Burj Khalifa tower (L) are switched off for an hour in Downtown Dubai, on March 23, 2013, as iconic landmarks and skylines are plunged into darkness for ‘Earth Hour.’ (Photo: AFP/Getty Images)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

This combination of two photos shows the National Congress in Brasilia before (top) and during Earth Hour on March 23, 2013. (Photo: AFP/Getty Images)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

In this composite image, The HSBC building and in blue lights the Standard Charter Bank Building are seen before (left) and after the lights were switched off to recognize Earth Hour on on March 23, 2013 in Hong Kong, Hong Kong. (Photo: Getty Images)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

Combo of two picture shows the Mostecka tower on the medieval Charle Bridge seen before and after submerging into darkness at 8:30 pm (local time) as part of the Earth Hour switch-off on March 23, 2013 in Prague. (Photo: AFP/Getty Images)

See the Photos: Cities Across the World Go Dark for Earth Hour to Fight Climate Change, Global Warming

The Brandenburger Gate is seen in darkness during Earth Hour in Berlin, Saturday, March 23, 2013. (Photo: AP)

​The Associated Press contributed to this report. This post may be updated.

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