Cities are the greenest possible way to live together, and perhaps the only way we can mitigate climate change, according to The Guardian's Leo Hollis, who cites SFI cities & urbanization research. 

"By living close together, sharing resources and reducing our energy usage we can minimise our footprint," Hollis writes."A recent study by the British physicist Geoffrey West shows that, when a city doubles in size, it becomes more efficient, increasing its carbon footprint only by 85%."

Read the article in The Guardian (April 11, 2014)