As an Earth Hour ambassador for the past 10 years, Li knows how gradually the movement has progressed. She revealed some of the difficulties and misunderstandings she has faced over the years when helping to promote the event during an exclusive interview with China Daily.

"Some people don't understand why we do this," she says. "They ask, how much energy can you save by turning off the lights for one hour? They think it's not as much as the waste that promoting the event causes."

Li says that she didn't give the event much thought when she decided to join Earth Hour in 2009, but she knew that environment and climate change were important issues. Buildings account for about one-third of the carbon emissions that scientists say will raise average global temperatures by 1.4 degrees Celsius and more this century, bringing floods and famines and putting millions of lives at risk.

Organizers of Earth Hour say that while switching off a light for one hour would have little impact on carbon emissions, the fact that so many people were taking part shows the interest and concern over the current climate crisis.

"When I return to the Bird's Nest, where Earth Hour started in China (in 2009), pictures of what we witnessed over the past 10 years keep running in my head, and I feel empowered to keep on going with it," Li says.

While the numbers of cities and people participating in Earth Hour has grown over the years, what has changed is Li's life and career.

She started a philanthropic operation called LOVE, which cooperates with the International Organization for Climate Change to plant industrial crops in rural areas that are better for the environment and the lives of farmers. Her outfit also calls for the reduction in the use of paper napkins at restaurants and promotes green commuting, encouraging people to walk, cycle or take buses to work instead of driving.

"More and more people understand that we should all undertake environmental protection work, and this is the reason I promote these ideas as an actress," says Li, adding that she felt encouraged by this.

Wang Shi, founder of China Vanke, one of China's major real estate enterprises, also joined Earth Hour as an ambassador. He says in a promotional video that he has quit using disposable bottled water and tableware. He brings his own slippers to hotels to avoid using disposable ones, and encourages Vanke employees to resist using similar items.

He says that about 58 billion disposable cups are used around the world every year. These single-use articles cost about 3.2 million mature trees and 100 billion liters of purified water during their manufacturing process.

"Half of the plastics that we use are single-use only, which is enjoyed by people for a short period of time, but takes the Earth hundreds of years to digest," he says.

In addition to the Bird's Nest, the Water Cube and the National Swimming Center, Hong Kong's Victoria Harbor also turned dark on March 24. Known for its stunning nighttime scenes, most of the famous landmarks on both sides of Hong Kong harbor, including the International Finance Center and Hong Kong Convention and Exhibition Center, had turned their lights off.

Global landmarks such as the Gelora Bung Karno stadium in Jakarta, the Acropolis in Athens, the Chain Bridge and Royal Palace in Budapest, and the Hassan II Mosque in Casablanca had switched their lights off to mark the Earth Hour event.