Bejing quadrupled in size in ten years

A new study shows that Beijing quadrupled in size between 2000 and 2009. The new buildings and roads alone were responsible for raising urban temperatures and pollution in the city.

The scientists used data from NASA’s QuikScat satellite to quantify urban growth based on changes in physical infrastructure, such as new buildings and roads. They found that the new infrastructure alone – not including the additional new city dwellers and their vehicles – changed heat, wind and pollution patterns in a ring around Beijing. For instance, winter temperatures increased by about 3 to 4 degrees Celsius and wind speed reduced by 1 to 3 metres per second, trapping pollution and making the city air more stagnant.

Buildings slow down winds just by blocking the air, and also by creating friction,” explains lead author Mark Jacobson of Stanford University. “You have higher temperatures because covering the soil reduces evaporation, which is a cooling process.”

Co-author Son Nghiem of NASA’s Jet Propulsion Laboratory says that the study set only the lower bounds for the impacts of urbanisation on local weather and pollution: “If you were to develop a city that didn’t allow any pollution sources, not even a single gas-powered car, you would still have these bad effects.”

 

Photo credit: “Beijing sunset” by Scottmeltzer – Own work. Licensed under Public Domain via Wikimedia Commons

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