A New Estimation of Urbanization's Contribution to the Warming Trend in China

The extent to which an urbanization effect has contributed to climate warming is under debate in China. Some previous studies have shown that the urban heat island (UHI) contribution to national warming was substantial (10%-40%). However, by considering the spatial scale of urbanization effects, this study indicates that the UHI contribution is negligible (less than 1%). Urban areas constitute only 0.7% of the whole of China. According to the proportions of urban and rural areas used in this study, the weighted urban and rural temperature averages reduced the estimated total warming trend and also reduced the estimated urban effects. Conversely, if all stations were arithmetically averaged, that is, without weighting, the total warming trend and urban effects will be overestimated as in previous studies because there are more urban stations than rural stations in China. Moreover, the urban station proportion (68%) is much higher than the urban area proportion (0.7%).