Controversial cool roof study is released

Researchers at Stanford University, Stanford, Calif., have authored a new study, "Effects of Urban Surfaces and White Roofs on Global and Regional Climate," which models climate response from 2005-25. The researchers say the urban heat-island effect is relatively minor in terms of any effect on global warming as a whole and light-colored, solar-reflective cool roofs may not help rein in climate change.

Mark Z. Jacobson, a professor of civil and environmental engineering at Stanford University, led the study and was assisted by Stanford University graduate student John Ten Hoeve. Jacobson says greenhouse gases and black carbon are the biggest contributors to climate change and, together, account for more than 95 percent of gross global warming since the Industrial Revolution. Jacobson also says that white solar-reflective roofs might add to, rather than lessen, global warming.

Stanford University News' announcement of the study says Jacobson's computer modeling concluded white roofs do cool urban surfaces. However, they cause a net global warming largely because they reduce cloudiness by increasing the stability of the air, thereby reducing the vertical transport of moisture and energy to clouds.