Dynamics of urban latent heat in response to climate change and urbanization: What would be a global threshold?

Urban latent heat is influenced by climate change-induced greening, CO₂ fertilization, and the urban heat island effect (Effect 1), which offsets reductions in latent heat caused by urbanization’s expansion of impermeable surfaces (Effect 2). The interaction between these effects remains unclear. The Hong Kong-Shenzhen region, characterized by a stable Leaf Area Index, intense anthropogenic activities, and abundant water resources, amplifies Effect 1. This region serves as an experimental site to explore global thresholds where these impacts reach equilibrium. Using Landsat and ERA5-Land data, monthly latent heat fluxes were computed from 1990 to 2019 using a stomatal process-based urban energy balance model. Shenzhen experienced a decline in latent heat (slope: −0.02), whereas Hong Kong showed an increase (slope: 0.08), confirming the presence of such thresholds. The region was segmented into 129 units, establishing a global benchmark indicating that Effect 1 significantly influences regional latent heat when the vegetation-to-impermeable surface ratio exceeds 2.71. Climate change impacts on Shenzhen’s latent heat increased by 94 %, compared to Hong Kong’s 55 %. Hong Kong demonstrates greater resilience to climate change than Shenzhen. This study underscores the importance of assessing urban dynamics for developing climate mitigation and sustainability strategies.