In what it's calling a "vote for the future of planet Earth," the World Wildlife Fund wants every light in the world to go dark for one hour on Saturday as a symbolic gesture to call for action on climate change.

It's called Earth Hour — and among the places where the lights will go out are the Eiffel Tower, the Bird's Nest Stadium in Beijing, the Pyramids of Giza and Niagara Falls.

And, for the first time in the event's three-year existence, the New York headquarters of the United Nations will also go dark, a move officials say will save $102, a figure that fluctuated wildly from its whopping initial estimate of $81,000 when requested from U.N. officials. After the story appeared on FOXNews.com, a spokeswoman called back to say their estimate was incorrect and the savings was $24,000, but then called back a third time to say it was really $102.

Earth Hour — 8:30 to 9:30 p.m in every time zone on the planet — promises to be “the largest demonstration of public concern about climate change ever attempted," U.N. Secretary-General Ban Ki-moon said earlier this month.

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But critics say the U.N.'s participation in the event is a "self-serving," thinly guised "gimmick" to sway public opinion ahead of the U.N.-led conference in Copenhagen in December at which world leaders will seek to approve a new global warming treaty.

"It's like a lot of what the U.N. does — it's a gimmick, it's empty, it's shallow and it's not going to lead to anything," said Thomas Kilgannon, president of Freedom Alliance, a Virginia-based nonprofit organization founded by Oliver North.

"The bigger problem is that they're doing this leading up to the conference in December. They're trying to consolidate their authority to push their agenda."

WWF organizers say nearly 2,900 cities worldwide will participate in Earth Hour, with at least 250 American cities among them, including Chicago, Dallas, Miami and San Francisco. Plenty of celebrities have signed on to the cause, including musicians Alanis Morissette, Melissa Etheridge and Wynonna Judd, as well as actors Edward Norton, Cate Blanchett, Kevin Bacon and Kyra Sedgwick.

And, of course, the United Nations.

"It's an attention-grabbing gesture that they expect to pay off for them big time," Claudia Rosett, a journalist-in-residence at the Foundation for the Defense of Democracies, told FOXNews.com. "For the U.N., climate change is the biggest cash cow of all time. They expect it to pay off for them big-time at the enormous and unaffordable expense of this and future generations."

Critics like Rosett say the U.N.'s role in Earth Hour is merely the public face of its much larger push to reorder the world's economy with new taxes, tariffs and subsidies for greenhouse gas abatement.

Click here for the details on the U.N.'s new plan to combat climate change.

"It's an immensely destructive gesture," Rosett said. "The U.N. has been busy manipulating and politicizing the science on this for years.... The whole climate obsession has the potential to make Oil for Food look like a drop in the ocean."

Based on average energy consumption levels from 2006-08, U.N. spokeswoman Vannina Maestracci said the world body's New York headquarters will save $102 while observing Earth Hour. Maestracci initially estimated the savings would be $81,000 before revising it to $24,300. She ultimately estimated the savings would be just $102 for the darkened hour.

Though she stressed that the U.N. is just one of many institutions across the world observing the event, she acknowledged it's a "strong symbol" in the climate change debate.

"It sends a strong message that we need a new agreement on climate change," Maestracci told FOXNews.com. "It's symbolic. It's part of an effort to mobilize support."

Whatever the savings, Rosett accused U.N. officials of distorting facts to make its participation in the event appear more impactful.

"That's a marvelous figure," Rosett said of the initial estimate. "If turning off the lights of the United Nations will save $81,000 an hour, it would be a great idea to keep them off every day of the year."

WWF spokeswoman Leslie Aun said Earth Hour will serve as a dramatic "visual message that the people of the world" are concerned about climate change.

"This is a reminder to our leaders around the world that people care about this issue," she said. "People told us last year they loved feeling connected to something big."

Asked to estimate how much energy could be saved worldwide during the 60 minutes of darkness, Aun replied, "We don't even calculate the emissions that we save in that hour. That's not the point."

But Bjorn Lomborg, author of "The Skeptical Environmentalist" and director of the Denmark-based think tank Copenhagen Consensus Centre, said the event could actually increase emissions.

"When asked to extinguish electricity, people turn to candlelight," Lomborg wrote in an op-ed in The Australian. "Candles seem natural, but are almost 100 times less efficient than incandescent light globes, and more than 300 times less efficient than fluorescent lights. If you use one candle for each extinguished globe, you're essentially not cutting CO2 at all, and with two candles you'll emit more CO2. Moreover, candles produce indoor air pollution 10 to 100 times the level of pollution caused by all cars, industry and electricity production."

Dr. Kenneth Green, a resident scholar on environmental science at the American Enterprise Institute, said Earth Hour shouldn't even be considered an environmental activity, since there will be no tangible benefits.

"If the U.N. is trying to show it's really committed to the Earth," he said, "they should scrap the giant fleet of black limousines they drive around in and buy hybrid cars in the United States to help the economy of the country they're in.

"That's the real tragedy in what this symbolizes. They’ve taken the one thing that symbolizes man's advancement over animals — that is, man's ability to create light — and they've turned it into a bad thing.

"It's the reversal of the Enlightenment. This is 'the Disenlightenment.'"