Lights went out for 60 minutes on purpose last weekend atop capitol domes, on famous landmarks and inside millions of home around the globe. The reason was an environmental observance called Earth Hour, organized for a second year by the World Wildlife Fund conservation group to show public support for saving energy and reducing greenhouse gas emissions blamed for global warming.

Saturday night's event was marked somehow in nearly 4,000 cities in 88 countries. Among iconic landmarks that went dark are the Pyramids at Giza, Egypt, the Acropolis in Athens, Big Ben in London, the Eiffel Tower in Paris, Sydney Harbor Bridge in Australia, the Empire State Building in New York, Sears Tower in Chicago, the Las Vegas Strip and dozens of state capitols across America.

Earth Hour began as a one-city observance in 2007, when 2.2 million homes and businesses in Sydney, Australia. switched off all lights for an hour. Last year, it went global as a demonstration of concern about climate change. The symbolic gesture is meant to show that everyone can help reduce carbon-dioxide emissions from burning coal and oil to generate electricity. Darkened skylines show how much energy is typically in use, which most scientists believe contributes to global warming.
"Even if you don't believe that the climate is changing, or that humans have an impact on climate, efficiency is a good thing," says Darron Collins of the World Wildlife Fund. "It makes sense to reduce individual consumption."

Student says: "It's important for adults to talk about these issues. . . . [But] if we're going to make a difference in our actions and our footprint on the planet, we have to start now with the young generation so it's not something that's going to be a drastic change -- it'll just be a part of their lives." -- Chloe Bens, eighth-grader in Regina, a city in the Canadian province of Saskatchewan

Critic says: "This is an entirely symbolic gesture that creates the mistaken impression that there are easy, quick fixes to climate change." -- Bjorn Lomborg, Danish policy center director and author of The Skeptical Environmentalist

Sponsor says: "What people like about Earth Hour is that it is fun and it tries to tap into people's creativity." -- Darron Collins, World Wildlife Fund managing director.