1. Definition
Urbanization is the process of urban development and is characterized by the expansion of
built-up areas and the growth of population in cities and towns. In the contexts of global change
research and climatic science, urbanization is usually regarded as a special manifestation of land
use and land cover change on a local scale.
Urbanization affects the local land surface, altering the surface climate in urban areas. The
urbanization-induced change in surface parameters is a fundamental reason for the formation and
evolution of urban climates. The urbanization-induced climate change (UICC) in urban areas
becomes a major component of urban climate change (UCC) which is additionally affected by
global climate change (GCC) and regional climate change (RCC) resulting from large-scale
anthropogenic and natural forcings, and by natural climate variability (NCV) resulting from the
internal oscillations of climatic system modes (Fig. 1). In decadal to centennial scales, the
large-scale anthropogenic forcings include the increased atmospheric greenhouse gas
concentration, aerosol emissions and land use and land cover (LULC) change, and the large-scale
natural forcings include solar activity and volcanic eruptions. It is obvious that the UCC represents
one of the most complicated changes in climate on the earth surface, caused by all the external
forcings and internal variability in various spatial scales, but obviously urbanization is one of the
major drivers. The climatic effect of urbanization or the UICC thus is a matter highly worthy of
attention.