Land-cover change and urban heat in a warming climate: a global satellite perspective.

The Urban Heat Island effect intensifies urban temperatures and exacerbates climate-related warming, yet how land cover (LC) buffers or amplifies this warming remains poorly quantified. This study analyzed satellite-derived land surface temperature (LST) across 100 cities from 2000 to 2020 using summer Landsat imagery at five-year intervals, evaluating LC-LST relationships through a three-level framework: net compositional change, pixel-level transition-specific pathways, and a Relative Temperature Index (RTI) revealing cross-city thermal signatures. LC change does not simply raise average temperatures - it preferentially amplifies the most dangerous heat. Extreme-heat metrics responded 1.5-1.7× more strongly than mean ΔLST to the same transitions. Water loss showed the strongest association with ΔLST increases (+ 3.7-4.9 K regardless of destination class), while impervious expansion was the most consistent predictor (+ 2.9-4.2 K across source classes) and the strongest significant predictor of net city-scale warming (R2 ≈ 0.23), alongside a significant cooling association with cropland gain. Mean LST across LC classes rose 1.3-2.6× faster than global mean land-only temperature over the study period, and extreme-heat metrics rose 2.9-4.5× faster, indicating urban surfaces amplify background climate warming beyond LC conversion alone. RTI analysis confirmed consistent relative thermal ordering across cities: impervious covers were consistently warmer than city means (RTI = 1.011), water cooler (RTI = 0.988), and vegetation near-neutral (RTI = 1.000). These results - consistent across three analytical levels, underscoring the value of this hierarchical framework - show that mitigation strategies should prioritize protecting water bodies and limiting impervious expansion, evaluated against extreme-heat metrics rather than mean temperature alone.