Mon Sep 16 16:16:03 UTC 2024: ## Urban Trees Offer Increased Cooling on Hotter Days, But Limitations Remain

**Nanjing, China** – A new study published in *Advances in Atmospheric Sciences* reveals that urban trees offer increased cooling benefits on hotter summer days, providing a potential solution to the growing urban heat island effect.

The study, conducted by researchers from Nanjing University, analyzed satellite data from 70 economically developed cities in China over a 17-year period (2003-2019). The research found that while urban trees provide a positive cooling effect, their efficiency actually increases on hotter days. This is due to the trees’ ability to cool the air through shade and evaporation.

However, the study also notes a potential limitation to this benefit. Research in Africa and India suggests that there may be a threshold temperature at which trees, in order to conserve water, close their stomata and significantly reduce their cooling efficiency. This diminished capacity could exacerbate heat conditions during extreme heat waves, highlighting the need for a multifaceted approach to urban heat mitigation.

“This underscores the need for a multifaceted approach to urban heat mitigation, particularly as cities face more frequent and severe heat waves,” said Jun Ge, corresponding author of the study.

The researchers emphasize the need to expand their analysis beyond China to gain a global perspective on the cooling efficiency of urban trees in response to rising temperatures. Future studies will also aim to incorporate the shading benefits of urban trees, which were not included in this initial analysis due to challenges in quantification through satellite data.

“Our ultimate goal is to understand the underlying mechanisms driving the cooling efficiencies of urban trees and to provide insights that can inform policy decisions on urban resilience strategies in the face of climate change,” said Ge.

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