Pharrell Williams is turning the Empire State Building yellow for the International Day of Happiness.

The 41-year-old will illuminate the iconic New York skyscraper in the bright colour today (20.03.15) to celebrate the occasion, led by the United Nations and Live Earth, in a bid to engage young people with the topic of climate change.

He explained: ''In a year where there is so much turmoil in the world, from social conflict to climate change, we need moments to stop and celebrate happiness.

''Protecting our planet is fundamental to the pursuit of human happiness and that is why we have chosen to support Live Earth's movement to raise a billion voices for climate action. We believe that happiness can change the world.''

The lights of the building will be changed at 2pm EST (6pm GMT), after which the 'Happy' hitmaker will speak to middle school students, alongside UN officials and climate experts, about the importance of taking action to curb climate change.

As part of the celebration, the chart-topper is also hosting a 'Happy Party'; encouraging people around the world to upload images of themselves to which will then be transformed into dancing animated images to raise awareness for the cause.