CHICAGO --If you notice that the lights are off on some of Chicago's landmarks this coming weekend -- don't be alarmed. It's because they are taking part in Earth Hour -- a global campaign to cut down on the use of electricity and help lower carbon emissions that change our climate. Hailed for its majestic skyscrapers and brightly shining lights, the Chicago skyline will go dark Saturday night between 8 and 9 p.m. More than two hundred buildings have agreed to power down their lights to mark earth hour. "The only lights that will be on for the most part will be the emergency lighting that's required to be on by the City of Chicago," said Thomas Keaty, General Manager, John Hancock Center The John Hancock Center plans to use the hour to make some permanent changes, including replacing about 200 incandescent bulbs. "We could cut energy costs in half for certain areas of the building by switching to more energy efficient compact fluorescent sources," said Chris Smith-Petersen, Philips Solid-State Lighting Solutions. The observatory will host an LED light show expected to be visible throughout most of the South Loop. It will double as an education station. "We didn't want to just have people come and look at the lights being turned off. So what we thought we would do is create an educational environment so anybody that does come up to view the outage has the opportunity to learn about energy efficient lighting," said Keaty. At Navy Pier, roughly 20,000 exterior lights will be shut off, including 16,000 on the Ferris Wheel. Restaurants and other indoor attractions will still be open but dim. "You might come to Navy Pier and find lights out at one of the restaurants for candlelight dining for instance. So everybody truly is encouraged to be a part of this great initiative," said Marilynn Gardner, General Manager, Navy Pier. The World Wildlife Fund started Earth Hour last year as a single event in Sydney, Australia. This year, Earth Hour will roll through 33 cities in 15 countries, marking the largest voluntary power down in history Quinn promotes Saturday's 'Earth Hour' Lt. Governor Pat Quinn honored the village of Homer Glen for its outdoor lighting ordinance. It cuts light pollution and increases energy efficiency. The ordinance passed back in December. Quinn is also promoting the second annual Earth Hour. Between 8 and 9 o'clock Saturday night, many cities and towns around the world and in Illinois will dim non-essential lights. Earth Hour will conserve electricity and lower carbon emissions. It's expected to be the largest voluntary action of its kind in history.