Hundreds of millions of people, businesses and governments around the world unite each year to support the largest environmental event in history – Earth Hour.

For Earth Hour 2012, more than 7,001 cities and towns in 151 countries around the world switched off their lights to send a powerful message for action on climate change. It also ushered in a new era with members going Beyond the Hour, as they commit to lasting action for the planet. Without a doubt, it’s shown how great things can be achieved when people come together for a common cause.

This year, Earth Hour 2013 will take place on 23 March, Saturday at 8.30 pm.

In 2006, World Wildlife Fund (WWF)-Australia inspired Sydney-siders to show their support for climate change action in the first ever Earth Hour event. In doing so, it showed everyone – from children to CEOs and politicians – that they have the power to change the world they live in.

Then in March 2007, 2.2 million individuals and more than 2,000 businesses in Sydney, Australia, turned their lights out for one hour to take a stand against climate change.

In 2008, the initial plan was just to take Earth Hour to the rest of Australia. But then the City of Toronto, Canada, signed up and it wasn’t long before 35 countries and almost 400 cities and towns were part of the event. It said something compelling to the world: that the climate challenges facing our planet are so significant that change needs to be global.

With the invitation to “switch off” extended to everyone, Earth Hour quickly became an annual global event. It’s scheduled on the last Saturday of every March – closely coinciding with the equinox to ensure most cities are in darkness as it rolled out around the Earth.

In 2011, Earth Hour saw hundreds of millions of people across 135 countries switch off for an hour. But it also marked the start of something new – going Beyond the Hour to commit to lasting action on climate change. And with the power of social networks behind the Earth Hour message, we attracted even more participation to build a truly global community committed to creating a more sustainable planet.

Earth Hour is organised by WWF. With almost 5 million supporters and a global network in over 100 countries/territories, it’s one of the world's largest and most respected independent conservation organisations. WWF’s mission is to stop the degradation of the Earth's natural environment and build a future where people live in harmony with nature.

Global warming is the greatest threat facing our planet today. A warming planet alters weather patterns, water supplies, seasonal growth for plants and a sustainable way of life for us, and the world’s wildlife. Climate change has already started, but it’s not too late to take action.

A continuous flow of energy from the sun heats the Earth. Naturally occurring gases in the atmosphere (known as greenhouse gases) trap this heat like a blanket, keeping the Earth at an average of 15 degrees Celsius – warm enough to sustain life. Carbon dioxide (CO2) is the most significant of these gases, but the amount of naturally produced CO2 is almost perfectly balanced by the amount naturally removed through photosynthesis and its dissolution in oceans.

However, the overuse of fossil fuels is leading to increased CO2 in the atmosphere, trapping more and more heat and warming the Earth. As a result, we’re seeing more dramatic weather patterns across the globe. The effects of Earth’s changing weather not only causes devastating natural disasters, but shrinking of the world’s ice shelves and glaciers due to warming sea water.