Extreme heat events piling up in cities around the world
FRISCO — The world’s urban areas are shaping their own local climate by affecting regional wind fields, and that is resulting in more frequent heatwaves, researchers say, reporting a climate “double-whammy” of global warming and an intensifying urban heat island effect.
Human activities and the built environment trap heat and prevent cities from cooling down, said UCLA geography professor Dennis Lettenmaier.
The well-established global temperature record comes from thousands of readings, many from stations that are untainted by human development, and scientists account for the heat island effect when they average overall global temperatures.
Heat island effect may drive rising sea levels, creating extra risk for populated coastal areas
By Summit Voice
SUMMIT COUNTY — Scientists with the UK’s University of Southampton say they may have documented another unanticipated global warming feedback loop, as sea surface temperatures in coastal regions appears to be rising up to 10 times faster than the global average.
Based on a study in the famed Venice Lagoon, the researchers said they think the warming is due at least in part to the urban heat island effect, with highly developed areas radiating extra heat to their surroundings. The findings suggest the sea surface temperature increases driven by the heat island effect may outpace other factors in coastal areas. Continue reading “Climate: Ocean temps rising especially fast along coasts”→
‘Cool Roofs’ program shows some promise, according to a new NASA study
By Summit Voice
SUMMIT COUNTY — Changing the color of roofs from black to white could help New York City move toward its goal of reducing greenhouse gas emissions by 30 percent in the next 20 years.
NASA researchers studying a pilot project on reducing the city’s urban heat island effect said they were able to measure significant differences during a July 2011 heat wave, when the dark, sunlight-absorbing surfaces of some New York City roofs reached 170 degrees.
Roofs covered with white material were measured at about 42 degrees cooler. On average through the summer of 2011, the pilot white roof surface reduced peak rooftop temperature compared to a typical black roof by 43 degrees Fahrenheit, according to the study, which was the first long-term effort in New York to test how specific white roof materials held up and performed over several years.
Widespread installation of white roofs, like New York City is attempting through the NYC CoolRoofs program, could reduce city temperatures while cutting down on energy usage and resulting greenhouse gas emissions, said Stuart Gaffin, a research scientist at Columbia University, and lead author on a paper detailing the roof study. The paper was published online Mar. 7, 2012, in Environmental Research Letters. Continue reading “Climate: New York seeks to reduce heat island effect”→
Painting city roofs white may actually result in a net warming effect, according to new study
By Summit Voice
SUMMIT COUNTY — The urban heat-island effect is only a small factor in the total amount of global warming since the Industrial Revolution, according to Stanford University scientists who quantified the contribution of the heat islands for the first time.
The study looked at surface temperatures in urban areas on a very fine one-kilometer-square grid, making the simulation both extremely detailed and globally comprehensive, looking at the impact of urban heat islands on global sea-surface temperatures, sea ice, atmospheric stability, aerosol concentrations, gas concentrations, clouds and precipitation.
“Between 2 and 4 percent of the gross global warming since the Industrial Revolution may be due to urban heat islands,” said Mark Z. Jacobson, a professor of civil and environmental engineering who led the study. He and graduate student John Ten Hoeve compare this with the greenhouse gas contribution to gross warming of about 79 percent and the black carbon contribution of about 18 percent. Continue reading “Urban ‘heat-islands’ only a small factor in global warming”→