Urban centres are subject to climatic conditions that represent a significant modification of the pre-urban climatic state, arising as a result of the modification of radiation, energy, and momentum exchanges resulting from the built form of the city, together with the emission of heat, moisture, and pollutants from human activities. ‘For the increasingly urbanized population of the world these effects are already of similar to, or of greater magnitude than, the climatic changes predicted to occur at larger scales as a result of the enhanced greenhouse effect’ (McKenry (2002) PPG 37, 4).

Increasingly, the focus of urban climate research is on understanding the fundamental processes that generate urban climates, not just the resultant effects. ‘While the stated rationale for much urban climate research is human health and well-being or energy and water consumption, urban climatologists often note the lack of communication of new knowledge and its implications to end-users, such as planners, architects and engineers’ (Souch and Grimmond (2006) PPG 30, 2). See Assimakopoulos et al. (2003) Atmos. Env. 37, 29 on pollution in ‘street canyons’. Mills (2006) Theoretical and Applied Climatology 84, 69–76 provides a useful summary of ways to modify urban climates, including outdoor landscaping, street orientation, zoning, and transport policy. See Chow and Hung (2014), SEAGA on the geography of urban climate change in Southeast Asia.