Are There Impacts of Urban Heat Island on Future Climate Change?

Abstract

The impacts of urban heat island effect on climate change in China and the world have been mostly conducted with meteorological station data for about last 50 years. Both the urban heat island effect and its contribution to climate warming have been calculated. For the quantification of urban heat island effect, one method is that observation stations are divided into degrees in accordance with city population, corresponding to the calculated population changes in different periods. Another method is that differences between the temperature at urban station and rural (countryside) station (or nearby sea surface temperature, SST). A recent study based on remote sensing data shows that heat island effect of the global mean daily temperature is 2.6◦C in summer, and 1.4◦C in winter [Zhang et al., 2010]. Research on China [Zhao, 1991; Ren et al., 2008; Jones et al., 2008] indicates that urban heat island effect contributes to climate warming by about 30%. Table 1 summarizes the contribution of urbanization to the warming for some studies in China [Zhao, 2011]. Because many gauge stations in China are located in urban regions, they are influenced by urbanization processes more clearly than before. Urban heat island effect is strengthening climate warming. Early research found that the mean warming was 0.06◦C per decade in China for 1951– 1989, in which urbanization caused the mean warming of 0.05◦C per decade and accounted for 83% of the total warming [Zhao, 1991]. It means that the key warming action was from urban heat island effect during 1950s–1980s. Recent study indicates that temperature increasing was obvious in China for 1961– 2004, the mean warming was 0.06–0.09◦C per decade up to 0.10◦C per decade in some significant areas. The annual mean warming rate due to urban heat island effect was 27%, and 18%–38% for the four seasons. It means that urban heat island effect contributed to 1/5–1/3 of the total warming in China in the last 50 years. Warming due to urban heat island effect in China was significant [Ren et al., 2008]. A new investigation estimated urban heat island effect in comparison with the nearby SST which was not influenced by urbanization. The warming trend in China for 1951– 2004 was 0.22◦C per decade. At the same time, the warming trend of SST was 0.14◦C per decade. Urban heat island effect caused warming of 0.08◦C per decade, which was 36% of the total warming. Urban heat island effect in China was more obvious than before due to urban population increase, urban areas