Europe's Environment Commissioner, Janez Potocnik has pledged to sing in front of an audience of at least 1,000 people if the same number agree to give up using their cars for a week.

The Commissioner made his promise as part of the Earth Hour Global Challenge. Speaking in a video, Potocnik said, "I believe that everyone has the power to change the world we live in," adding that it was a matter of plenty of small steps.

A very important first step is to think about ...