For the 11th year running, cities worldwide turned their lights off on Saturday(yesterday) to mark Earth Hour in a global call to action on climate change.

EARTH HOUR :

(i) Earth Hour is a worldwide movement organized by the World Wide Fund for Nature (WWF).
(ii) The event is held annually encouraging everyone to turn off their non-essential lights for one hour, from 8:30 to 9:30 p.m. towards the end of March,
(iii) The moment of darkness should also serve as a reminder of another problem that gets far less attention i.e. light pollution.