From his office in the Berkeley hills, Art Rosenfeld looks out on the heart of California’s Bay Area. The 87-year-old scientist keeps a pencil and a small notebook in his breast pocket, ready to jot down a quick note or make a calculation. With these simple tools he has been able to influence state and national energy policy over the years. But for now they stay tucked away as he enjoys the scenery. “I get a pretty good view of San Francisco,” Rosenfeld says.
While his vantage point has remained unchanged since beginning his career at Lawrence Berkeley National Laboratory in 1955, the view outside his window has changed considerably. The buildings are taller and more densely packed in on all sides of the bay. And from Rosenfeld’s bird’s-eye view, he sees that many of these buildings now boast noticeably brighter rooftops than they did even a few years ago.
This brightening is a direct result of Rosenfeld’s vision. For decades he has promoted “cool” roofs, which are lighter in color than traditional black slabs and therefore reflect more of the sun’s heat. Cool roofs save money by keeping indoor temperatures more comfortable in warm weather and reducing the need for air conditioning. And since smog forms more rapidly at higher temperatures, reducing excess urban heat can also make city air safer to breathe. To top it off, cooler temperatures can make heat waves less hazardous to city-dwellers.
On a larger scale, the impact can be even greater. A global campaign to brighten cities could cancel out some of the warming caused by greenhouse gases. This is because reducing energy absorption at Earth’s surface decreases the amount of heat these gases can trap in the atmosphere. Of this planetary conversion, Rosenfeld says “it’s like taking half of the world’s cars off the road for 20 years.”
With the United States leading the charge, that reality may not be far away. Cities from San Francisco to New York are combating rising temperatures and improving air quality – dampening the effects of climate change in the process – by brightening their roofs. In a way, it’s as though Rosenfeld has taken his pencil to city skylines; instead of shading in the changes he has influenced, though, he uses the other end to erase black roofs.