In an effort to raise awareness about global warming, the city of London turned out its lights last week. The voluntary blackout happened on June 21 between 9pm and 10pm and included many notable building such as Tower Bridge, Parliament, and Buckingham Palace. Piccadilly Circus also participated turning out its advertising lights for the first time since World War II. London isn't the first city to do this. They follow in the footsteps of Sydney, Paris and Hong Kong. London estimates that they collectively turned out 2 million lights saving 750 MWh of electricity in 1 hour. I like this idea because turning out lights is such a simple thing, but the effect of seeing such well known attractions in darkness has quite an impact. It would be great to see some more permanent energy savings come out of this.