Intense drought and vegetation browning exacerbate air temperature rise in unirrigated peri-urban areas under global warming

Abstract

Cities are particularly vulnerable to climate change, which continues to drive rising air temperatures. The morphology of a city also influences local climate through diverse surface properties and configurations, leading to diverse responses to warming trends. We examined the impact of climate change on Santiago, Chile, a valley city with a semi-arid climate. Near-surface air temperature and rainfall data from Chile’s Bureau of Meteorology over the past 63 years were collected from three different local climate zones (LCZs) in a peri‑urban, urban park, and residential areas. The research employed regression analysis, a seasonal time series model, and standardised anomalies to assess air temperature and rainfall trends. Results show that the peri‑urban area has experienced the highest rate of warming and the greatest decline in rainfall, alongside a doubling of the warming rate in recent years. Discrepancies in maximum and minimum temperature trends resulted in varying daily temperature ranges (DTR) across LCZs. The peri‑urban area also displayed significant intra-annual variability in air temperature and rainfall, leading to trend variations over the years in contrast to the other LCZs. Our findings underscore the accentuated impact of climate change in the peri‑urban area due to its permeable bare soil surfaces with an increase of 0.36 ◦C per decade of warming, compared to the areas characterised by impermeable surfaces and well-irrigated green spaces of 0.25 ◦C per decade on average. It highlights the importance of analysing urban air temperatures through LCZ classifications, challenging the conventional urban-rural temperature dichotomy that underpins urban heat island assessments.