Nonlinear causal relationships between urbanization and extreme climate events in China

Abstract

China has undergone rapid urbanization since 1980s, which could in return alter the occurrences of regional weather and sequential hazards, posing challenges to sustainable development of human society. However, casual relationships between urbanization and climate extremes are still poorly understood. In this study, causal relationships between urbanization and extreme temperature/precipitation are quantified using a nonlinear Granger causality framework. Causal hotspots are observed not only in major urban agglomerations but well as in less urbanized areas. For both temperature and precipitation extremes, the impact of urbanization could last within 5 years (mainly 4 years).The causality varies greatly with different climate background, but the contribution of urbanization to extreme temperature and precipitation exhibits a high level of consistency in individual city. Urbanization has profoundly causal relationships with nighttime extreme heat with higher morbidity and mortality to urban residents. Averagely, urbanization causally accounts for almost 36.9% to temperature extremes. On the other hand, urbanization has higher casual contribution to total precipitation. The inland regions are more likely to be affected by urbanization than coastal regions due to weak monsoon influence. On average, urbanization causally accounts for almost 39.7% to precipitation indices. This study innovatively reveals the significant causal relationships between urbanization and extreme temperature/precipitation changing patterns of China, providing valuable insights for developing sustainable cities in the future.