With a bang on his drum, a man shouted, “Welcome to this year’s Earth Hour, where we cut the power!”

As businesses and residents turned off their lights at 8:30 p.m., people who had gathered Saturday night to play instruments and celebrate Earth Hour shouted the chant to passersby from a concrete stage on North Fourth Avenue.

From the Fox Tucson Theatre downtown to restaurants on Fourth Avenue to the mall at the University of Arizona, parts of Tucson went dark from 8:30 p.m. to 9:30 p.m. in commemoration of Earth Hour, a call by the World Wildlife Fund to react to climate change. The movement began in Australia in 2007 and turned into a global movement last year with 50 million people participating.

Bison Witches, 326 N. Fourth Ave., gave patrons the option of specials on dark beers.

Ian Carstensen, a manager of the restaurant, said the restaurant was participating in Earth Hour to raise awareness of the “social responsibility we all have to conserve the resources we’re running out of.”

Delectables Restaurant and Catering, 533 N. Fourth Ave., asked customers to eat by candlelight. From inside the restaurant, music could be heard from the band playing on the outdoor stage down the street, celebrating the hour in the dark.

“This is a symbolic gesture here in Tucson to get people thinking consciously about their impact on the environment,” said Kurt Tallis, marketing and events director for the Fourth Avenue Merchants Association, which sponsored the Earth Hour events on Fourth Avenue. “In one night we can see how we can all come together to make a change.”

The University of Arizona Mall was darkened south of the Flandrau Science Center, creating optimal stargazing conditions for people who came out with their telescopes to view Saturn, the moon and constellations.

Stephen Pompea, the manager of science education for the National Optical Astronomy Observatory, brought out powerful telescopes to view the Orion Nebula and Saturn because of the lessening of light pollution from the city.

Joe Frannea, the manager of the Southern Arizona section of the International Dark Sky Association, said that light pollution can encroach on Tucson all the way from the outskirts of Phoenix.

"It’s impressive to see how many people will make a difference tonight," Frannea said. "Light impacts wildlife and us. People just don’t realize it."

People participated in Earth Hour across the globe. Lights at historic monuments from the Eiffel Tower to the Sydney Opera House were turned off in commemoration of the event. The goal was to have one billion participants to get the word out on global climate change and the effects of human energy consumption on the planet.

"This is to get people in the mindset of a collective consciousness about the climate change," Carstensen said. "I know it’s really important to me to get this message out there."

SEE IMAGES OF EARTH HOUR IN CITIES ACROSS THE GLOBE: