It’s official: an eye-watering 500 million people are now using Facebook. But as the social networking site celebrates this latest milestone, another one is in the making: almost half a million of its users have joined one of our groups calling for the company to ditch dirty coal – and go 100 percent renewable instead.

"This is an important milestone for all of you who have helped spread Facebook around the world," Mark Zuckerberg, Facebook’s CEO, said in a blog post to celebrate his company’s latest figures this week. The data also shows that of its half a billion users, 250 million use Facebook every single day.

Impressive? For sure. But how much more impressive would it be if all that social networking going on via Facebook across this planet was powered by renewable energy – and not by the dirtiest source of energy and the largest single source of global warming pollution in the world: coal.

Yet, that’s exactly what Facebook is planning to use for a massive new data centre in Prineville, Oregon. Facebook says that the US$ 180 million project will be extremely energy efficient – and that’s laudable. Saving energy makes good business sense, and it's good for the environment too.

But it’s not nearly enough.

Tell Facebook now that you want them to show true climate leadership by setting a strong policy in this

area. Join one of our groups that send a clear message to those in charge at Facebook HQ: “We want Facebook to use 100 percent renewable energy.”

There’s one in English, in Spanish, in French and in Dutch.

What better time to send this message to your social networking site than now, as the company is riding high on its worldwide success? We’re saying: Congratulations, Facebook, on making it to half a billion! We’re saying: Now is the time to go 100 percent renewable! This is your chance to make a real difference.