Painting roofs white or covering them with a reflective coating would be more effective at cooling cities like London than vegetation-covered “green roofs,” street-level vegetation or solar panels, finds a new study led by UCL researchers. Conversely, extensive use of air conditioning would warm the outside environment by as much as 1 degree C in London’s dense city centre, the researchers found. The research, published in Geophysical Research Letters, used a three-dimensional urban climate model of Greater London to test the thermal effects of different passive and active urban heat…