Satellite-derived Land Surface Temperatures Strongly Mischaracterise Urban Heat Hazard

TL;DR

Satellite-derived land surface temperature is often misused as a proxy for human thermal comfort in urban heat studies, leading to potential misguidance in adaptation policies.

Contribution

This paper critically examines the limitations of satellite-based land surface temperature as an indicator of human thermal stress and advocates for a nuanced, multidisciplinary approach.

Findings

LST poorly correlates with near-surface air temperature during daytime.

Misuse of LST inflates perceived urban heat risks.

Proper interpretation of LST requires complementary data and models.

Abstract

Escalating urban heat, driven by the convergence of global warming and rapid urbanization, is a profound threat to billions of city dwellers. The science directing urban heat adaptation is strongly influenced by studies that use satellite-based land surface temperature (LST), which is readily available globally and address data gaps in cities, particularly in the Global South. LST, however, is a poor surrogate for near-surface air temperature, physiologically relevant human thermal comfort, or direct human heat exposure. This flawed practice leads to issues for several downstream use cases by inflating adaptation benefits, distorting the magnitude and variability of urban heat signals across scales, and thus misguiding urban adaptation policy. We argue that satellite-based LST must be treated as a distinct indicator of surface climate, which, though relevant to the urban surface energy budget, can be frequently decoupled from human-relevant thermal impacts especially during daytime. Only by a disciplined application of this variable, combined with complementary datasets, process-based and data-driven models, as well as interdisciplinary collaboration, can urban adaptation design and policy be effectively advanced.