On April 22, more than one billion people around the globe will participate in Earth Day 2012 and help Mobilize the Earth. People of all nationalities and backgrounds will voice their appreciation for the planet and demand its protection. Together we will stand united for a sustainable future and call upon individuals, organizations and governments to do their part.
Earth day, April 22, comes on a Sunday this year, making a weekend paint project a perfect way to celebrate. Just painting the surface of a black roof white can lower its temperature on a hot afternoon by as much as 50 to 65 degrees. And cooling down the house is good for the wallet and the environment.
Research finds that if all of the world’s urban areas were outfitted with white roofs and light-colored pavement, it would cool the planet by as much as 0.13 degrees Fahrenheit, saving up to 150 billion tons of carbon dioxide emissions--equal to 50 years’ worth of emissions from all the world’s cars.
The new work, by Hashem Akbari and colleagues of Concordia University in Montreal, used estimates for the amount of urban roof and pavement surfaces globally combined with climate models to determine the effect on global temperatures of changing the reflectivity of a surface, known as its albedo. Albedo values range from zero, for a completely black surface, to one, for a perfectly white surface. Akbari’s team said resurfacing roofs could easily increase their albedo by 0.25 on average, while a 0.15 average increase is easy to achieve for pavement. This would translate to an overall increase in albedo for an entire city of around 0.1.
Lightening a roof can be as simple as painting it white or choosing a lighter colored roof material. Some higher-tech shingles exist that are dark yet still reflect infrared light. For pavement, the necessary increase in albedo can usually be achieved by incorporating light-colored aggregate into the asphalt.
“Every roof is going to be changed every now and then,” Akbari said, creating an opportunity for the roof to be replaced with a lighter material. The same goes for pavement. Every bit counts: each square meter of roof that’s made 0.01 albedo units lighter is the equivalent of taking over 15 pounds of carbon dioxide out of the atmosphere. It saves on air conditioning bills in the summer--perhaps 10 to 15 percent--since less heat is absorbed by the building, and cool roofs may last longer, since they expand and contract less with heat and cold.
For flat roofs, it makes no aesthetic difference to make them white since they can’t be seen from the ground. Many states have building codes that require commercial roofs to be made white when they are redone, and cool roofs are a part of the federal Energy Star program.
Several cities have taken steps to incorporate white roofs. Through its NYC °CoolRoofs program, which provides no-cost labor to coat roofs, and with homeowner’s own efforts, New York has whitened 2.5 million square feet of roof, said Danielle Grillo, Executive Director of Community Partnerships at the New York City Department of Buildings. That’s the equivalent of 750 New Yorkers not driving for a year.
Earth Day is celebrated around the world on April 22. Some cities start celebrating a week in advance, ending the recognition of Earth Week on April 22nd. Others host month long events to stress the importance of teaching about our environment. The United Nations celebrates Earth Day each year on the March equinox, which is often March 20, a tradition which was founded by peace activist John McConnell in 1969.
Year Equinox Earth Day April 22 Earth Day Celebration
2012 March 20 April 22
2013 March 20 April 22
2014 March 20 April 22
2015 March 20 April 22
How to Contribute
Paint Your Roof White for Earth Day
Painting roofs white and lightening pavement worldwide could have significant climate change benefits--equivalent to taking all the world's cars of the road for 50 years.
Making these surfaces more reflective also saves on air conditioning bills.
Many cities and states have programs to encourage cool roofs.
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